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Aim: Genetic influences on cerebral activity have been described previously, but data are scarce in preterms. We aimed to investigate whether a genetic influence causes amplitude-integrated electroencephalography (aEEG) signals to differ between singletons and twin preterm newborns. Methods: This was a retrospective single-centre study conducted at Innsbruck Medical University Hospital, Austria. Preterm infants born before 32 weeks of gestation between 6 November 2010 and 6 December 2022 were eligible for the study. The aEEG was analysed for the total maturation score, its component scores and the number of sleep--wake cycles per hour. Results: We enrolled 240 preterm twin infants (57.5% male) with a mean gestational age of 30 (range: 24-32) weeks and a mean birth weight of 1324 (range: 600--2116) grams. We compared 240 singleton matched preterms. No differences were found between preterm singletons and twin preterm infants regarding the total maturation and component scores, or the number of sleep--wake cycles. aEEG showed no difference between monozygotic and dizygotic twins. Conclusion: Compared to singletons, twin infants born preterm showed no differences in aEEG signals in the first 4 weeks of life. Future studies should include more complex non-invasive functional neuroimaging methods to gain more insight into this important topic. [ABSTRACT FROM AUTHOR]

Background: The way in which socioeconomic status (SES) moderates the etiology of reading attainment has been explored many times, with past work often finding that genetic influences are suppressed under conditions of socioeconomic deprivation and more fully realized under conditions of socioeconomic advantage: a gene–SES interaction. Additionally, past work has pointed toward the presence of gene–location interactions, with the relative influence of genes and environment varying across geographic regions of the same country/state. Method: This study investigates the extent to which SES and geographical location interact to moderate the genetic and environmental components of reading attainment. Utilizing data from 2,135 twin pairs in Florida (mean age 13.82 years, range 10.71–17.77), the study operationalized reading attainment as reading comprehension scores from a statewide test and SES as household income. We applied a spatial twin analysis procedure to investigate how twin genetic and environmental estimates vary by geographic location. We then expanded this analysis to explore how the moderating role of SES on said genetic and environmental influences also varied by geographic location. Results: A gene–SES interaction was found, with heritability of reading being suppressed in lower‐ (23%) versus higher‐SES homes (78%). The magnitude of the moderating parameters were not consistent by location, however, and ranged from −0.10 to 0.10 for the moderating effect on genetic influences, and from −0.30 to 0.05 for the moderating effect on environmental influences. For smaller areas and those with less socioeconomic variability, the magnitude of the genetic moderating parameter was high, giving rise to more fully realized genetic influences on reading there. Conclusions: SES significantly influences reading variability. However, a child's home location matters in both the overall etiology and how strongly SES moderates said etiologies. These results point toward the presence of multiple significant environmental factors that simultaneously, and inseparably, influence the underlying etiology of reading attainment. [ABSTRACT FROM AUTHOR]

Objective: The main risk factor for preterm delivery (PTD; <37 gestational weeks) is having a history of PTD. The aim of this research was to compare the risk for recurrent PTD following twin versus singleton gestation PTD. Methods: A retrospective population‐based cohort study was performed, including all women who had two consecutive pregnancies, the first of which ended with PTD. The incidence of PTD recurrence was compared between women with PTD in twin versus singleton gestation. Multivariable logistic models were used to study the association between twinning status and PTD recurrence, and specifically by gestational age of the first PTD, inter‐pregnancy interval (IPI), and mode of conception. Results: The study population included 15 590 women, of whom 1680 (10.8%) had twins in their index pregnancy and 13 910 (89.2%) had singletons. The incidence of recurrent PTD was 10.5% (n = 177) following twin PTD versus 21.9% (n = 3044) following singleton PTD (adjusted odds ratio = 0.50, 95% confidence interval 0.32–0.76, while controlling for confounding variables). The results were consistent while stratifying by IPI, gestational age of the first PTD, or mode of conception. Conclusions: Women with PTD in twin gestations are at lower risk for recurrent PTD compared with women with singleton PTD. Women with preterm delivery (PTD) in twin versus singleton gestations are at lower risk for recurrent PTD, regardless of gestational age, inter‐pregnancy interval or conception mode. [ABSTRACT FROM AUTHOR]

Background: Findings from randomized trials (RCTs) on cervical pessary treatment to prevent spontaneous preterm birth are inconsistent. Objectives: Our hypothesis suggests that adhering to the European Medical Device Regulation (MDR) and following the instructions for use are essential prerequisites for successful therapy. Conversely, the non‐adherence to these guidelines will probably contribute to its failure. Search Strategy and Selection Criteria: Based on validated criteria from integrity assessments we performed a systematic review identifying 14 RCTs evaluating the effect of cervical pessaries. Data Collection and Analysis: We analyzed the implications of 14 criteria each accounting for 0–2 points of a score reflecting the clinical evaluation plan (CEP) as proposed by the MDR to evaluate the risk–benefit ratio of medical devices. Main Results: Seven RCTs in each singleton and twin pregnancies (5193 "cases") were included, detecting a high heterogeneity within control groups (I2 = 85% and 87%, respectively, P < 0.01). The CEP score varied from 11 to 26 points for all studies. The most common reasons for low scores and potential data compromise were poor recruitment rates, no (completed) power analysis, and no pre‐registration, but mainly non‐adherence to technical, biological, and clinical equivalence to the instructions for use as required by the MDR. All trials with score values greater than 20 had applied audit procedures. Within this group we found significantly reduced rates of spontaneous preterm birth at less than 34 weeks within the pessary group in singleton (odds ratio 0.28; 95% confidence interval 0.12–0.65) and twin pregnancies (odds ratio 0.30; 95% confidence interval 0.13–0.67). Similarly, there was a significant reduction in the composite poor neonatal outcome in singleton (odds ratio 0.25; 95% confidence interval 0.10–0.61) and twin pregnancies (odds ratio 0.54; 95% confidence interval 0.35–0.82) after a pessary as compared with controls. Conclusion: Non‐audited RCTs and meta‐analyses mixing studies of different clinical quality as pre‐defined by a CEP and the MDR pose the risk for erroneous conclusions. Synopsis: Our findings underline the importance of clinical audit procedures for randomized trials and specifically for the effect of cervical pessaries. [ABSTRACT FROM AUTHOR]

We assessed prevalence and correlates of differential maternal‐infant bonding (i.e., experiencing a stronger bond with one baby vs. the other) in mothers of twins, focusing on aspects of maternal mental health, well‐being, and pregnancy/birth that have been previously linked with maternal‐infant bonding. Participants (N = 108 American women, 88.89% White, 82.41% non‐Hispanic, aged 18–45, who gave birth to twins in the past 6–24 weeks) were recruited from postpartum support websites. Participants completed a Qualtrics survey assessing pregnancy/birth history, symptoms of depression and anxiety, sleep, stress, romantic relationship satisfaction, and postpartum bonding. Twenty‐six participants (24.07%) reported a bonding discrepancy. These participants endorsed higher symptoms of depression and anxiety, lower relationship satisfaction, lower average postpartum bonding, higher general and parenting stress, and longer pregnancy (all ps >.05). Greater degree of bonding discrepancy correlated with more depression, higher parenting stress, longer pregnancy, and lower relationship satisfaction (all ps >.05). Mothers of twins may benefit from postpartum mental health support, stress management strategies, and interventions to improve bonding. Future work should assess the role of breastfeeding difficulties, delivery method, birth‐related trauma, infant regulatory capacity, and temperament. Longitudinal studies will help test cause and effect and potential long‐term repercussions of maternal‐infant bonding discrepancies. [ABSTRACT FROM AUTHOR]

Objective: Reward‐based eating drives are putative mechanisms of uncontrolled eating implicated in obesity and disordered eating (e.g., binge eating). Uncovering the genetic and environmental contributions to reward‐related eating, and their genetic correlation with BMI, could shed light on key mechanisms underlying eating and weight‐related disorders. Method: We conducted a classical twin study to examine how much variance in uncontrolled eating phenotypes and body mass index (BMI) was explained by genetic factors, and the extent that these phenotypes shared common genetic factors. 353 monozygotic twins and 128 dizygotic twins completed the Reward‐based Eating Drive 13 scale, which measures three distinct uncontrolled eating phenotypes (loss of control over eating, preoccupation with thoughts about food, and lack of satiety), and a demographic questionnaire which included height and weight for BMI calculation. We estimated additive genetic (A), common environmental (C), and unique environmental (E) factors for each phenotype, as well as their genetic correlations, with a multivariate ACE model. A common pathway model also estimated whether genetic variance in the uncontrolled eating phenotypes was better explained by a common latent uncontrolled eating factor. Results: There were moderate genetic correlations between uncontrolled eating phenotypes and BMI (.26–.41). Variance from the uncontrolled eating phenotypes was also best explained by a common latent uncontrolled eating factor that was explained by additive genetic factors (52%). Discussion: These results suggest that uncontrolled eating phenotypes are heritable traits that also share genetic variance with BMI. This has implications for understanding the cognitive mechanisms that underpin obesity and disordered eating. Public Significance: Our study clarifies the degree to which uncontrolled eating phenotypes and BMI are influenced by shared genetics and shows that vulnerability to uncontrolled eating traits is impacted by common genetic factors. [ABSTRACT FROM AUTHOR]

Epigenetic clocks based on DNA methylation have been known as biomarkers of aging, including principal component (PC) clocks representing the degree of aging and DunedinPACE representing the pace of aging. Prior studies have shown the associations between epigenetic aging and T2DM, but the results vary by epigenetic age metrics and people. This study explored the associations between epigenetic age metrics and T2DM or glycemic traits, based on 1070 twins (535 twin pairs) from the Chinese National Twin Registry. It also explored the temporal relationships of epigenetic age metrics and glycemic traits in 314 twins (157 twin pairs) who participated in baseline and follow‐up visits after a mean of 4.6 years. DNA methylation data were used to calculate epigenetic age metrics, including PCGrimAge acceleration (PCGrimAA), PCPhenoAge acceleration (PCPhenoAA), DunedinPACE, and the longitudinal change rate of PCGrimAge/PCPhenoAge. Mixed‐effects and cross‐lagged modelling assessed the cross‐sectional and temporal relationships between epigenetic age metrics and T2DM or glycemic traits, respectively. In the cross‐sectional analysis, positive associations were identified between DunedinPACE and glycemic traits, as well as between PCPhenoAA and fasting plasma glucose, which may be not confounded by shared genetic factors. Cross‐lagged models revealed that glycemic traits (fasting plasma glucose, HbA1c, and TyG index) preceded DunedinPACE increases, and TyG index preceded PCGrimAA increases. Glycemic traits are positively associated with epigenetic age metrics, especially DunedinPACE. Glycemic traits preceded the increases in DunedinPACE and PCGrimAA. Lowering the levels of glycemic traits may reduce DunedinPACE and PCGrimAA, thereby mitigating age‐related comorbidities. [ABSTRACT FROM AUTHOR]

Objective Methods Results Conclusion To compare the risk of intrapartum cesarean delivery (CD) between patients with twin and singleton pregnancies undergoing a trial of labor and identify risk factors for intrapartum CD in twin pregnancies.The present study was a retrospective cohort study of patients with a twin or singleton pregnancy who underwent a trial of labor at ≥340/7 weeks in a single center (2015–2022). The primary outcome was the rate of intrapartum CD. In twin pregnancies, this outcome was limited to CD of both twins. The association of plurality with intrapartum CD was estimated using multivariable Poisson regression.A total of 20 754 patients met the study criteria, 669 of whom had a twin pregnancy. Patients with twins had a greater risk of intrapartum CD (of both twins) than those with singleton pregnancies (22.1% vs 15.9%, respectively; aRR 1.38 [95% CI: 1.15–1.66]), primarily due to a greater risk of failure to progress. In addition, 4.1% of the twin pregnancies had a CD for the second twin, resulting in an overall CD rate in twin pregnancies of 26.2%. Variables associated with intrapartum CD in twin pregnancies included nulliparity (aOR 3.50, 95% CI: 2.34–5.25), birthweight discordance >20% (aOR 2.47, 95% CI: 1.27–4.78), and labor induction (aOR 1.64, 95% CI: 1.07–2.53). The rate of intrapartum CD was highest when all three risk factors were present (67% [95% CI: 41%–87%]).Twin pregnancies are associated with a greater risk of intrapartum CD than singleton pregnancies. Information on the individualized risk of intrapartum CD may be valuable when counseling patients with twins regarding mode of delivery. [ABSTRACT FROM AUTHOR]

The phenomenon of familial clustering in depression is well established, yet the mechanisms by which depression is transmitted within families remain poorly understood. In the current study, we investigate the familial genetic and environmental transmission of depression by incorporating data from both adolescent twins and their parents. A total of 987 twin families were recruited from the Beijing Twin Study. Depression assessments were conducted for both adolescents and their parents. Twins' depression was assessed through reports from both the twins themselves and their parents, while parental depression was assessed by parental self‐report. We employed a nuclear twin family model to examine genetic and environmental influences on adolescent depression. Our results, based on both self‐ and parent‐report, demonstrate significant additive and dominant genetic influences on depression. We also found mild yet significant sibling environmental influences, while familial environmental influences were absent. Notably, parent‐reported depression showed higher heritability but lower unique environmental influences compared with self‐reported depression. These results highlight the important role of genetic transmission and sibling environmental transmission in explaining depression. Our study delineates the underlying mechanism of familial transmission in depression and can inform early treatments to halt transmission during adolescence. [ABSTRACT FROM AUTHOR]

Objective: To estimate the effect of antenatal corticosteroids on newborn respiratory morbidity in twins. Design: Regression discontinuity applied to population‐based birth registry data. Setting: British Columbia, Canada, 2008–2018. Population: Twin pregnancies admitted for birth between 31+0 and 36+6 weeks of gestation. Methods: During our study period, Canadian clinical practice guidelines recommended antenatal corticosteroid administration for imminent preterm birth up to 33+6 weeks. We used a logistic model to compare the predicted risks of our outcomes among pregnancies admitted for birth immediately before this clinical cut‐point (higher probability of exposure to antenatal corticosteroids) versus immediately after it (lower probability). Main outcome measures: Our primary outcome was a composite of newborn respiratory distress or in‐hospital death. Our secondary outcome was a composite of newborn respiratory intervention or in‐hospital death. Results: Among 2524 pregnancies (5035 liveborn twins), 47% of admissions before 34+0 weeks of gestation were exposed to antenatal corticosteroids but only 4.2% of admissions after this cut‐point were exposed. The risk of newborn respiratory distress or in‐hospital mortality increased abruptly at 34+0 weeks, corresponding to a protective effect of treatment (risk ratio [RR] 0.69, 95% CI 0.53–0.90; risk difference [RD] −12 cases per 100 births, 95% CI −20 to −4.1). There was no clear evidence for or against an effect on newborn respiratory intervention or in‐hospital death (RR 0.89, 95% CI 0.70–1.13; RD −4.2 per 100, 95% CI −13 to +4.2). Conclusions: Our findings provide evidence for the effectiveness of antenatal corticosteroids in preventing adverse newborn respiratory outcomes in twins. [ABSTRACT FROM AUTHOR]

Background: Stress is a universal phenomenon and one of the most common precipitants of insomnia. However, not everyone develops insomnia after experiencing a stressful life event. This study aims to test aspects of Spielman's '3P model of insomnia' (during adolescence) by exploring the extent to which: (a) insomnia symptoms are predicted by polygenic scores (PGS); (b) life events predict insomnia symptoms; (c) the interaction between PGS and life events contribute to the prediction of insomnia symptoms; (d) gene–environment interaction effects remain after controlling for sex. Methods: The sample comprised 4,629 twins aged 16 from the Twin Early Development Study who reported on their insomnia symptoms and life events. PGS for insomnia were calculated. In order to test the main hypothesis of this study (a significant interaction between PGS and negative life events), we fitted a series of mixed effect regressions. Results: The best fit was provided by the model including sex, PGS for insomnia, negative life events, and their interactions (AIC = 26,158.7). Our results show that the association between insomnia symptoms and negative life events is stronger for those with a higher genetic risk for insomnia. Conclusions: This work sheds light on the complex relationship between genetic and environmental factors implicated for insomnia. This study has tested for the first time the interaction between genetic predisposition (PGS) for insomnia and environmental stressors (negative life events) in adolescents. This work represents a direct test of components of Spielman's 3P model for insomnia which is supported by our results. [ABSTRACT FROM AUTHOR]

Objective: To compare morbidity, as measured by length of stay in the neonatal intensive care unit (NICU), in twin and singleton gestations classified as small‐for‐gestational age (SGA) according to estimated fetal weight < 10th percentile on twin or singleton growth charts. Methods: NICU length of stay was compared in 1150 twins and 29 035 singletons that underwent ultrasound assessment between 35 + 0 and 36 + 6 weeks' gestation. Estimated fetal weight was obtained from measurements of head circumference, abdominal circumference and femur length using the Hadlock formula. Gestational age was derived from the first‐trimester crown–rump length measurement, using the larger of the two twins. Singletons and twins were compared in terms of NICU admission rate and length of stay according to classification as SGA by the Fetal Medicine Foundation singleton and twin reference distributions. Results: The overall proportions of twins and singletons admitted to NICU were similar (7.3% vs 7.4%), but twins tended to have longer lengths of stay in NICU (≥ 7 days: 2.4% vs 0.8%; relative risk (RR), 3.0 (95% CI, 1.6–4.4)). Using the singleton chart, a higher proportion of twins were classified as SGA compared with singletons (37.6% vs 7.0%). However, the proportion of SGA neonates entering NICU was similar (10.2% for twins and 10.1% for singletons) and the proportion of SGA neonates spending ≥ 7 days in NICU was substantially higher for twins compared with singletons (3.7% vs 1.4%; RR, 2.6 (95% CI, 1.4–4.7)). Conclusions: When singleton charts are used to define SGA in twins and in singletons, there is a greater degree of growth‐related neonatal morbidity amongst SGA twins compared with SGA singletons. Consequently, singleton charts do not inappropriately overdiagnose fetal growth restriction in twins and they should be used for monitoring fetal growth in both twins and singletons. © 2023 International Society of Ultrasound in Obstetrics and Gynecology. [ABSTRACT FROM AUTHOR]

Objective: To assess whether the risk for future diabetes is higher among women diagnosed with gestational diabetes (GD) during twin versus singleton gestations. Method: A retrospective cohort study was performed including all women who delivered at a tertiary medical center between the years 1991 and 2021 and had at least one GD diagnosis. The first GD diagnosis per women was defined as the index pregnancy. Women diagnosed with GD during multiple gestations were compared with women diagnosed with GD during singleton gestations. The outcomes included first hemoglobin A1C (Hba1C) level > 6.4 mg/dL post partum, and the highest level measured during the follow‐up period of up to 30 years. Multivariable logistic and Cox proportional analysis were used to compare the risk between the two groups while adjusting for confounding variables. Results: The current study included 13 770 mothers, with 458 patients (3.3%) diagnosed with GD during twin gestations and 13 312 (96.7%) during singleton gestations. The mean follow‐up was 12.25 ± 9.3 years. Mothers of both groups did not differ in age at index pregnancy; however, mothers of twins were more likely to conceive following fertility treatments. Incidence of diabetes and prediabetes (defined as Hba1C > 6.4 and >5.7, respectively) were lower among the twin‐gestation group, both during the 6‐month postpartum period (for diabetes: 15.5% vs 22.1%; odds ratio [OR], 0.65 [95% confidence interval (CI), 0.46–0.91]) and during the long‐term follow‐up (for diabetes: 31.8% vs 40.7%; OR, 0.68 [95% CI, 0.52–0.88]). These results remained significant in the multivariable analysis, while accounting for age, ethnicity, and fertility treatments. Conclusion: GD diagnosis during multiple versus singleton gestations is associated with a lower risk for future diabetes. Synopsis: Women diagnosed with gestational diabetes during twin gestation are at lower risk for future diabetes, suggesting that gestational diabetes criteria should account for multiple gestation. [ABSTRACT FROM AUTHOR]

Twinning‐induced plasticity steel is characterized by the presence of twins and austenite at room temperature. In this work, Fe–24Mn–3Al–1Ni–2Si–0.06C steel is cold‐rolled at 30, 50, and 80% thickness reduction and subsequently annealed at temperatures between 300 and 1100 °C for 15 min. The microstructure and hardness are analyzed, and dislocation density, stacking fault, and twin probability are calculated using the diffraction method based on the intensity of X‐rays generated in a synchrotron facility. The Rietveld analysis using Materials Analysis Using Diffraction (MAUD) software is performed, and Popa Model is employed. Cold rolling increases hardness due to the formation of deformation twins, stacking fault, and dislocation in different degrees depending on the thickness reduction. During annealing, recrystallization influences the parameters obtained by X‐Ray diffraction such as stacking fault probability and dislocation density. [ABSTRACT FROM AUTHOR]

Objective: Several personality theories distinguish between rather genetically rooted, universal dispositional traits (DTs) and rather environmentally shaped, more contextualized characteristic adaptations (CAs). However, no study so far has compared different measures of theoretically postulated DTs and CAs regarding their environmental and genetic components while considering differences in measurement abstraction and reliability. This study aims to bridge this gap by testing the assumed differences in the sensitivity to environmental influences based on representative sets of DTs (Big Five and HEXACO domains and facets) and CAs (goals, interests, value priorities, religiousness, and self‐schemas). Method: Using intra‐class correlations and running extended twin family and spouses‐of‐twins model analyses, we analyzed a large data set (N = 1967) encompassing 636 twin pairs, 787 parent‐offspring dyads, and 325 spouses/partners. Results: Findings consistently support lower environmentality of DTs compared to CAs. On average, more than half of reliable variance in DTs was genetic, whereas the reverse was found for CAs. Larger environmental components in CAs were primarily attributable to larger individual‐specific effects (beyond error of measurement) and factors shared by spouses. Conclusions: Findings are discussed against the background of the definitional distinction between DTs and CAs and the value of extended twin family data. [ABSTRACT FROM AUTHOR]

The investigation of environmental effects on clinical measurements using individual samples is challenging because their genetic and environmental factors are different. However, using monozygotic twins (MZ) makes it possible to investigate the influence of environmental factors as they have the same genetic factors within pairs because the difference in the clinical traits within the MZ mostly reflect the influence of environmental factors. We hypothesized that the within‐pair differences in the traits that are strongly affected by genetic factors become larger after genetic risk score (GRS) correction. Using 278 Japanese MZ pairs, we compared the change in within‐pair differences in each of the 45 normalized clinical measurements before and after GRS correction, and we also attempted to correct for the effects of genetic factors to identify Cytosine‐phosphodiester‐Guanine (CpG) sites in DNA sequences with epigenetic effects that are regulated by genetic factors. Five traits were classified into the high heritability group, which was strongly affected by genetic factors. CpG sites could be classified into three groups: regulated only by environmental factors, regulated by environmental factors masked by genetic factors, and regulated only by genetic factors. Our method has the potential to identify trait‐related methylation sites that have not yet been discovered. [ABSTRACT FROM AUTHOR]

During research conducted in 2019 regarding pelvic shape in population groups and its effects on successful delivery, one of the individuals studied was a Late Dynastic/Coptic Egyptian female mummy approximately 14–17 years old (USNM catalogue number 258601). She had an associated fetus that was wrapped and placed between her legs during mummification (USNM 258602). In 1908, the mother and child were excavated and autopsied for analysis. Field notes from 1908 said she had died from obstetric complications. For our 2019 study, the mummy was CT scanned to acquire the measurements of her pelvis and determine if cephalopelvic disproportion played a role in her death. While examining the CT images, elements of what was believed to be the fetus were identified in the mother. However, there were repetitions of elements, and a second fetus was discovered in the chest cavity of the mummy. The mother was carrying twins. For this study, re‐scanning by CT and plain film radiography of the torso were performed on the mother as well as plain film radiography on the external fetus. Additionally, records and photographs from the 1908 expedition were reviewed to gather additional information on the mummy. Results note this mummy was pregnant with twins and in the middle of the birthing process at the time of her death. [ABSTRACT FROM AUTHOR]

Objective: Supporting families during the first 1001 days from conception to the age of two is vital for setting the emotional, cognitive, and physical building blocks for children's futures. Families with twins, triplets, or higher order multiples (multiple birth families) have unique challenges due to caring for more than one baby at the same time. Therefore, identifying the needs of multiple birth families is necessary to provide optimum support during the first 1001 critical days. Design: A rapid review was undertaken to synthesize knowledge of the needs of multiple birth families in the United Kingdom (UK) during the first 1001 critical days. Findings from five databases (MEDLINE, APA PsycArticles, APA PsycInfo, CINAHL, and Web of Science) for peer‐reviewed studies and grey literature published between 2012 and 2022 were synthesized. Fifteen studies were reviewed using narrative synthesis. Results: Multiple birth families have unique and complex emotional and practical needs across the first 1001 critical days, and in particular, the first‐year post birth, impacted further by complicated pregnancies and prematurity. Needs were identified within the four key themes: high risk pregnancy and birth; transformed reality of raising multiples; inadequate support; and positively affecting experiences. Health professional support was inconsistent and particularly lacking in intrapartum, postnatal, and community care including transition. Conclusion: Multiple birth families' needs should be considered in the design and delivery of care within the first 1001 critical days, especially within the first year after birth. Multiples specific advice across the first 1001 critical days is needed and training for health professionals to adapt universal advice for this population is one way to achieve this. Further research is needed to ensure this advice is evidence based and effective. [ABSTRACT FROM AUTHOR]

Background: The association of sleep bruxism with mortality has not been studied. Objectives: Altogether 12 040 subjects from the nationwide Finnish twin cohort were included in the analyses. We examined whether self‐reported sleep bruxism is associated with increased risk of mortality, and if so, whether the effect is independent of known common risk factors. The time span of the follow‐up was 30 years. Methods: Cox proportional hazards regression models (Hazard Ratios and their 95% Confidence Intervals) adjusted by age, sex and covariates were used to assess the effect of baseline bruxism status in 1990 on future mortality in 1990–2020. Results: The risk of mortality among all participants (n = 12 040), independent of missing covariates and adjusted by age and sex, was 40% higher in weekly bruxers than in never bruxers (HR 1.40, 95% CI 1.16–1.68, p <.001). However, when adjusted by all studied covariates, (n = 11 427) the risk was no longer observed (HR 1.04, 95% CI 0.86–1.25, p =.717). Despite the overall lack of between bruxism and mortality after adjustment for covariates, we examined the cause‐specific risks for major cause‐of‐death groups. There were no substantial associations of weekly bruxism with major disease outcomes by the fully adjusted hazard ratios for them. Conclusion: Bruxism does not kill—in line with its definition of being rather a behaviour (with all its phenotypes) than a disease. [ABSTRACT FROM AUTHOR]

Background: Due to different assessment modes employed, a clear picture of the prevalence of sleep bruxism across time cannot be formed. Moreover, studies on the persistent or fluctuating nature of sleep bruxism have yielded divergent and even contradictory results. The aim of the present study was to evaluate in a nationwide twin cohort whether self‐reported sleep bruxism was correlated longitudinally, pairwise and cross‐twin over a 20‐year period. Objectives: Self‐reported bruxism was assessed in 1990 and 2011 by mailed questionnaires in the Finnish Twin Cohort study of same‐sex twins born 1945–1957. Methods: We assessed the phenotypic stability over time for all participating individuals (n = 4992). Among zygosity verified pairs (n = 516 MZ and n = 837 DZ), we estimated the cross‐sectional zygosity correlations and the zygosity‐specific cross‐twin cross‐time correlations. Results: Reported bruxism appeared rather persistent over time without significant difference regarding zygosity. The overall phenotypic longitudinal correlation was 0.540 and somewhat higher in men (0.596) than in women (0.507). Pairwise trait correlations in 1990 and 2011 were higher in MZ than in DZ pairs. The cross‐twin cross‐time correlations were higher in MZ twins than in DZ twins, but less than the cross‐sectional MZ and DZ pairwise correlations. Conclusions: The higher correlation of reported sleep bruxism in the cross‐twin cross‐time analyses in MZ than in DZ pairs implies a genetic background for bruxism persistence. Also, bruxism over time in individual twins appears to be fairly persistent and somewhat higher in men than women. [ABSTRACT FROM AUTHOR]

Objective: To compare the maternal and neonatal outcomes of twin pregnancies between vertex and nonvertex presentations of the second twin in vaginal delivery. Methods: In this unicentric retrospective cohort study, we collected data from 213 cases of vaginal twin deliveries from January 2016 to July 2020. Participants were divided into the vertex‐vertex presentation group (VV) and vertex‐breech presentation group (VB). Data on maternal and neonatal outcomes were compared between groups. Results: Among the 213 mothers and 426 infants (213 twin pairs), there were 140 women in the VV group and 73 women in the VB group (65.73% vs. 34.27%). Infants in the VB group had a higher incidence of admission to NICU (51.43% vs. 68.49%, p = 0.017), lower 1‐min (11.43% vs. 28.77%, p < 0.001) and 5‐minute Apgar scores (1.43% vs. 4.11%, p = 0.043) for the second twin. However, after the adjustment for sex of the twin, birth weight, chorionicity, and gestational age, the greater risk of admission to NICU and low 5‐min Apgar score was no longer significantly different. Conclusion: VB twins are at no greater overall risk of a poor outcome due to breech presentation in the second twin. However, the presentation of the second fetus represents a risk factor for a low 1‐min Apgar score. Obstetricians and midwives should consider appropriate interventions for second twins who present breech versus vertex. [ABSTRACT FROM AUTHOR]

Objective: To characterize fetal growth in dichorionic twins using individualized growth assessment (IGA), a method based on individual growth potential estimates. Methods: This secondary analysis included 286 fetuses/neonates from 143 dichorionic twin pregnancies that were part of the ESPRiT (Evaluation of Sonographic Predictors of Restricted Growth in Twins) study. The sample was subcategorized according to birth weight into appropriate‐for‐gestational‐age (AGA) (n = 243) and small‐for‐gestational‐age (SGA) (n = 43) cohorts. Serial biometric scans evaluating biparietal diameter, head circumference (HC), abdominal circumference, femur diaphysis length and estimated weight at 2‐week intervals were used to evaluate fetal growth, while measurements of birth weight, crown–heel length and HC determined neonatal growth outcome. Six abnormalities (hypoxic ischemic encephalopathy, periventricular leukomalacia, necrotizing enterocolitis, respiratory distress, sepsis and death) constituted the evaluated adverse neonatal outcomes (ANO). IGA was used to: evaluate differences in second‐trimester growth velocities between singletons (from a published dataset) and dichorionic twins (138 AGA twins with normal third‐trimester growth); describe the degree to which actual third‐trimester growth in twins followed expected growth (111 AGA twins, normal fetal growth and neonatal growth outcomes); determine if the fetal growth pathology score 1 (–FGPS1) could detect, quantify and classify twin growth pathology (224 AGA, 42 SGA); and assess the relationship between –FGPS1 and ANO (24 SGA twins with progressive growth restriction confirmed by abnormal neonatal growth outcome). Results: The differences in second‐trimester growth velocity between singletons and twins (means and variances) were small and not statistically significant. Percent deviations from the expected third‐trimester size trajectories were within the 95% reference ranges derived from singletons at 95.7% (1677/1752) of timepoints studied. Abnormal growth was detected in 37.9% of AGA twins and 85.7% of SGA twins. Growth restriction was more heterogeneous in AGA twins, while in SGA twins progressive growth restriction was the principal type (66.7%). –FGPS1 patterns previously defined in singletons classified 97.5% of pathological twin cases. In our most severe form of growth restriction (progressive), there were only three (12.5%) ANOs related to growth abnormalities, all in cases with –FGPS1 values more negative than –2.0%. Using these criteria, the frequency of ANO was 33%. Conclusions: With respect to growth, dichorionic twins can be considered as two singletons in the same uterus. Normally growing dichorionic twins have the same growth potential as singletons with normal growth outcome. These twins also follow expected third‐trimester growth trajectories with the same precision as do singletons. Third‐trimester growth pathology can be detected, quantified and classified using –FGPS1 as in singletons. Limited evidence of a relationship between fetal growth abnormalities and adverse neonatal outcome was found. © 2023 International Society of Ultrasound in Obstetrics and Gynecology. [ABSTRACT FROM AUTHOR]

Objectives: To determine the accuracy of sonographic fetal weight estimation in predicting birth weight (BW) and BW discordance in twin gestations, and to evaluate maternal and fetal characteristics that may affect the accuracy of this assessment. Methods: This was a retrospective cohort study of all twins delivered at a single tertiary medical center between 2010 and 2021. Twin gestations for which sonographic estimation of fetal weight was performed within the week preceding delivery were included. Statistical analysis was performed to evaluate the strength of the correlation between sonographic estimated fetal weight (EFW) and BW, and to determine the impact of maternal and fetal factors on the accuracy of sonographic estimation. Results: The study included 2154 twin pregnancies. There was a strong correlation between sonographic EFW and corresponding BW for all twins (r = 0.922; P < 0.001). Strong correlations were observed for both the presenting and non‐presenting cotwin (r = 0.921 and r = 0.922, respectively; both P < 0.001), as well as the larger and smaller cotwin (r = 0.928 and r = 0.934, respectively; both P < 0.001). The overall mean ± SD absolute error of sonographic EFW was 7.41 ± 6.81%. This error was greater for the non‐presenting cotwin compared with the presenting cotwin (7.99 ± 6.12% vs 7.17 ± 5.64%; P < 0.001), and for the smaller cotwin compared with the larger cotwin (8.56 ± 7.50% vs 6.58 ± 5.47%; P < 0.001). Advanced gestational age at scanning was correlated inversely with the mean absolute error of sonographic EFW. Multivariate logistic regression indicated that an earlier gestational age at scanning, being the non‐presenting cotwin and being the smaller cotwin were independent risk factors for sonographic EFW inaccuracy. Pregnancies in which the presenting twin was estimated to be the smaller cotwin had twice the rate of false‐positive BW discordance compared with pregnancies in which the presenting twin was estimated to be the larger cotwin (36.0% vs 13.0% for BW discordance > 15%, 35.0% vs 17.0% for BW discordance > 20% and 37.7% vs 12.1% for BW discordance > 25%; all P < 0.001). The error in sonographic EFW discordance was not related to chorionicity, the position of the presenting fetus or gestational age at the time of fetal weight estimation. Conclusions: Sonographic estimation of fetal weight within 7 days before delivery accurately predicts BW in twin pregnancy. Sonographic EFW accuracy is reduced for the non‐presenting twin, the smaller cotwin and when delivery occurs at an earlier gestational age. Sonographic estimation of fetal weight discordance is less accurate when the presenting twin is the smaller cotwin. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology. [ABSTRACT FROM AUTHOR]

A substantial literature in political psychology has emphasized the importance of personality traits for understanding differences in political participation. One such trait is extraversion. However, the causal status of this relationship is complicated by a number of issues, not least genetic confounding stemming from the heritability of both personality traits and political participation. This study confirms the well‐established naive relationship between extraversion and participation, but goes on with (a) a discordant MZ twin design and (b) a new approach using measured genetic variation, or a polygenic index, in the given trait (extraversion) to assess the causal nature of this relationship. First, utilizing variation in extraversion and participation within identical twin pairs shows that twins with higher extraversion do not participate more. Second, random variation within fraternal twin pairs in a polygenic index of extraversion does predict trait extraversion, but does not predict political participation. In summary, previously identified associations between extraversion and political participation are not likely to be causal, but instead reflect common underlying familial factors. [ABSTRACT FROM AUTHOR]

Research into the family of the Counts Swéerts‐Sporck raised doubts regarding their biographical data, particularly concerning a child who died in 1817, later identified as Philipp Swéerts‐Sporck, and his siblings Joseph and Barbara. These were alleged to include a pair of dizygotic twins, but DNA could not be used to clarify their relationships. Carbon and nitrogen isotopes were therefore measured in their first permanent molars, whereas Philipp's biological age was estimated based on his skeleton. Philipp died at an older age than the written sources claim; an isotopic similarity was found between Joseph and Barbara, but Philipp differed. [ABSTRACT FROM AUTHOR]

Background: Parents' and peers' cannabis use are well‐documented predictors of youth cannabis use, however, relatively little is known about the influence of siblings' cannabis use. Hence, this meta‐analysis investigated the association between sibling‐youth cannabis use (disorder) and explored moderation by sibling type (monozygotic‐ vs. dizygotic‐ vs. non‐twins), age, age spacing, birth order, gender, and gender constellations (same‐ vs. mix‐ gender pairs). When comparison data of parents' and peers' cannabis use (disorder) were also available in the included studies, separate meta‐analyses on associations between parent‐youth and peer‐youth cannabis use (disorder) were additionally conducted. Methods: Studies were selected if they included 11‐ to 24‐year‐old participants, and investigated associations between cannabis use (disorder) among those youth and their siblings. These studies were retrieved via a search in seven databases (e.g., PsychINFO). A multi‐level meta‐analysis using a random effects model was performed on the studies, and heterogeneity analyses and moderator analyses were also conducted. PRISMA guidelines were followed. Results: We retrieved 20 studies (most of which originated from Western cultures) with 127 effect sizes for the main sibling‐youth meta‐analysis and found a large overall effect‐size (r =.423), implying that youth had higher cannabis use rates when their sibling used cannabis, and this association was stronger for monozygotic twins and for same‐gender sibling pairs. Finally, a medium effect size existed for the associations between parent‐youth cannabis use (r =.300) and a large effect size for peer‐youth cannabis use (r =.451). Conclusions: Youth are more likely to use cannabis when their siblings use cannabis. This sibling‐youth cannabis use association existed for all sibling constellations, was larger than the association between parent‐youth cannabis use, and was similar in magnitude compared to the association between peer‐youth cannabis use—suggesting both genetic and environmental influences (e.g., social‐learning) between siblings. Hence, it is important not to neglect sibling influences when treating youth cannabis use (disorder). [ABSTRACT FROM AUTHOR]

Background: Emotional symptoms, such as anxiety and depressive symptoms, are common during adolescence, often persist over time, and can precede the emergence of severe anxiety and depressive disorders. Studies suggest that a vicious cycle of reciprocal influences between emotional symptoms and interpersonal difficulties may explain why some adolescents suffer from persisting emotional symptoms. However, the role of different types of interpersonal difficulties, such as social isolation and peer victimisation, in these reciprocal associations is still unclear. In addition, the lack of longitudinal twin studies conducted on emotional symptoms during adolescence means that the genetic and environmental contributions to these relationships during adolescence remain unknown. Methods: Participants (N = 15,869) from the Twins Early Development Study completed self‐reports of emotional symptoms, social isolation and peer victimisation at 12, 16 and 21 years old. A phenotypic cross‐lagged model examined reciprocal associations between variables over time, and a genetic extension of this model examined the aetiology of the relationships between variables at each timepoint. Results: First, emotional symptoms were reciprocally and independently associated with both social isolation and peer victimisation over time, indicating that different forms of interpersonal difficulties uniquely contributed to emotional symptoms during adolescence and vice versa. Second, early peer victimisation predicted later emotional symptoms via social isolation in mid‐adolescence, indicating that social isolation may constitute an intermediate pathway through which peer victimisation predicts longer‐term emotional symptoms. Finally, individual differences in emotional symptoms were mostly accounted for by non‐shared environmental factors at each timepoint, and both gene–environment and individual‐specific environmental mechanisms were involved in the relationships between emotional symptoms and interpersonal difficulties. Conclusions: Our study highlights the necessity to intervene early in adolescence to prevent the escalation of emotional symptoms over time and to consider social isolation and peer victimisation as important risk factors for the long‐term persistence of emotional symptoms. [ABSTRACT FROM AUTHOR]

Background: Attention‐deficit/hyperactivity disorder (ADHD) is an increasingly commonly diagnosed neurodevelopmental condition. One possibility is that this reflects a genuine increase in the prevalence of ADHD due to secular environmental changes, yet this hypothesis remains untested. We therefore investigated whether the genetic and environmental variance underlying ADHD, and traits of ADHD, has changed over time. Methods: We identified twins born from 1982 to 2008 from the Swedish Twin Registry (STR). We linked the STR with the Swedish National Patient Register and Prescribed Drug Register to identify diagnoses of ADHD and prescriptions of ADHD medication for these twins. We also utilized data collected from participants in the Child and Adolescent Twin Study in Sweden (CATSS), born from 1992 to 2008. Their parents completed a structured ADHD screening tool, which was used to measure traits of ADHD and assign broad screening diagnoses of ADHD. We used the classical twin design to test whether the degree to which variation in these measures was influenced by genetic and environmental variation changed over time. Results: We included 22,678 twin pairs from the STR and 15,036 pairs from CATSS. The heritability of ADHD in the STR ranged from 66% to 86% over time, although these fluctuations were not statistically significant. We observed a modest increase in variance in ADHD traits, from 0.98 to 1.09. This was driven by small increases in the underlying genetic and environmental variance, with heritability estimated as 64%–65%. No statistically significant changes in variance in screening diagnoses were observed. Conclusions: The relative contribution of genetic and environmental factors to ADHD has remained stable over time, despite its increasing prevalence. Thus, changes in the underlying etiology of ADHD over time are unlikely to explain the increase in ADHD diagnoses. [ABSTRACT FROM AUTHOR]

Objective: To investigate the national prevalence and prenatal detection rate (DR) of major congenital heart disease (mCHD) in twin pregnancies without twin‐to‐twin transfusion syndrome (TTTS)‐associated CHD in a Danish population following a standardized prenatal screening program. Methods: This was a national registry‐based study of data collected prospectively over a 10‐year period. In Denmark, all women with a twin pregnancy are offered standardized screening and surveillance programs in addition to first‐ and second‐trimester screening for aneuploidies and malformation, respectively: monochorionic (MC) twins every 2 weeks from gestational week 15 and dichorionic (DC) twins every 4 weeks from week 18. The data were retrieved from the Danish Fetal Medicine Database and included all twin pregnancies from 2009–2018, in which at least one fetus had a pre‐ and/or postnatal mCHD diagnosis. mCHD was defined as CHD requiring surgery within the first year of life, excluding ventricular septal defects. All pregnancy data were pre‐ and postnatally validated in the local patient files at the four tertiary centers covering the entire country. Results: A total of 60 cases from 59 twin pregnancies were included. The prevalence of mCHD was 4.6 (95% CI, 3.5–6.0) per 1000 twin pregnancies (1.9 (95% CI, 1.3–2.5) per 1000 live births). The prevalences for DC and MC were 3.6 (95% CI, 2.6–5.0) and 9.2 (95% CI, 5.8–13.7) per 1000 twin pregnancies, respectively. The national prenatal DR of mCHD in twin pregnancies for the entire period was 68.3%. The highest DRs were in cases with univentricular hearts (100%) and the lowest with aortopulmonary window, total anomalous pulmonary venous return, Ebstein's anomaly, aortic valve stenosis and coarctation of the aorta (0–25%). Mothers of children with prenatally undetected mCHD had a significantly higher body mass index (BMI) compared to mothers of children with a prenatally detected mCHD (median, 27 kg/m2 and 23 kg/m2, respectively; P = 0.02). Conclusions: The prevalence of mCHD in twins was 4.6 per 1000 pregnancies and was higher in MC than DC pregnancies. The prenatal DR of mCHD in twin pregnancies was 68.3%. Maternal BMI was higher in cases of prenatally undetected mCHD. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the mother–child separation rate in twin pregnancies delivered in maternity units offering an appropriate level of neonatal care. Methods: JUMODA is a French, prospective, population‐based cohort study of twin deliveries, including 7998 women who gave birth in maternity units with appropriate levels of neonatal care based on thresholds for weeks of gestational age (wGA) and birth weight according to French guidelines: level I (≥36 wGA), IIA (≥34 wGA), IIB (≥32 wGA and ≥ 1500 g), and IIII (<32 wGA or < 1500 g). The primary outcome was mother–child separation, defined as the transfer of at least one twin or the mother to another hospital. Results: Mother–child separation occurred in 2.1% of pregnancies. This rate was significantly higher in level I (4.8%, 95% confidence interval [CI] 1.5–12.5) and IIA (3.4%, 95% CI 2.4–4.7) compared with level IIB (1.6%, 95% CI 1.1–2.3) and level III maternity units (2.1%, 95% CI 1.9–2.8). In level IIA units, the rate of mother–child separation was higher for babies born between 34 and 36 wGA (8.3%) than for those born at 36 wGA or beyond (1.7%). In level IIb, the rate of mother–child separation for babies born between 32 and 34 wGA (7.5%) was higher than for those born between 34 and 36 wGA (2.1%) and at 36 wGA or beyond (0.9%). Conclusion: Mother–child separation rates were low but differed by level of care. By using specific thresholds for twins to define levels of care, rather than data from singleton births, one‐fifth of mother–child separations could have been avoided. Synopsis: Rates of mother–child separation after twin birth in a maternity unit with appropriate level of neonatal care were low but differed by level of care. [ABSTRACT FROM AUTHOR]

We propose a unique, minimal assumption, approach based on variance analyses (compared with standard approaches) to investigate genetic influence on individual differences on the functional connectivity of the brain using 65 monozygotic and 65 dizygotic healthy young adult twin pairs' low‐frequency oscillation resting state functional Magnetic Resonance Imaging (fMRI) data from the Human Connectome Project. Overall, we found high number of genetically‐influenced functional (GIF) connections involving posterior to posterior brain regions (occipital/temporal/parietal) implicated in low‐level processes such as vision, perception, motion, categorization, dorsal/ventral stream visuospatial, and long‐term memory processes, as well as high number across midline brain regions (cingulate) implicated in attentional processes, and emotional responses to pain. We found low number of GIF connections involving anterior to anterior/posterior brain regions (frontofrontal > frontoparietal, frontotemporal, frontooccipital) implicated in high‐level processes such as working memory, reasoning, emotional judgment, language, and action planning. We found very low number of GIF connections involving subcortical/noncortical networks such as basal ganglia, thalamus, brainstem, and cerebellum. In terms of sex‐specific individual differences, individual differences in males were more genetically influenced while individual differences in females were more environmentally influenced in terms of the interplay of interactions of Task positive networks (brain regions involved in various task‐oriented processes and attending to and interacting with environment), extended Default Mode Network (a central brain hub for various processes such as internal monitoring, rumination, and evaluation of self and others), primary sensorimotor systems (vision, audition, somatosensory, and motor systems), and subcortical/noncortical networks. There were >8.5‐19.1 times more GIF connections in males than females. These preliminary (young adult cohort‐specific) findings suggest that individual differences in the resting state brain may be more genetically influenced in males and more environmentally influenced in females; furthermore, standard approaches may suggest that it is more substantially nonadditive genetics, rather than additive genetics, which contribute to the differences in sex‐specific individual differences based on this young adult (male and female) specific cohort. Finally, considering the preliminary cohort‐specific results, based on standard approaches, environmental influences on individual differences may be substantially greater than that of genetics, for either sex, frontally and brain‐wide. [Correction added on 10 May 2023, after first online publication: added: functional Magnetic Resonance Imaging. Added: individual differences in, twice. Added statement between furthermore ... based on standard approaches.] [ABSTRACT FROM AUTHOR]

Objectives: Accumulating evidence has revealed that dental anxiety is robustly associated with dental care‐related pain and discomfort, but also with the personality trait of neuroticism (i.e. the relatively stable disposition to experience the world as distressing, threatening and unsafe). However, there is a near absence of research on these risk factors in samples for which genetic information is available. With the aim of arriving at a more refined understanding of dental anxiety, this twin cohort study assessed genetic and environmental influences on neuroticism, dental care‐related pain and dental anxiety, and the relation between these phenotypes. Methods: Participants were recruited from the Norwegian Twin Registry, and data collections were carried out in 1992–98 (Time 1) and 2011 (Time 2). Well‐validated questionnaires were used to assess the study variables, including Corah's Dental Anxiety Scale, the Numerical Pain Rating Scale, the NEO Personality Inventory Revised (Time 2) and Eysenck's Personality Questionnaire (Time 1). Pearson correlation analysis and generalized estimating equations (GEE) were used to investigate phenotypic associations. Analyses of genetic and environmental influences were performed using Cholesky modelling. Results: A total of 746 monozygotic (MZ) and 770 dizygotic (DZ) twins in the age group of 50–65 participated in the study. Moderate estimates of heritability for dental anxiety (0.29), treatment‐related pain (0.24) and neuroticism (0.45–0.54) were found. Cholesky modelling showed furthermore that neuroticism assessed at Time 1 and Time 2 was related to dental anxiety and pain via both genetic and individual‐specific environmental pathways, albeit not very strongly. The particularly high phenotypic correlation observed between dental care‐related pain and anxiety (r =.68) was explained by both overlapping genetic and individual‐specific environmental influences (the genetic and environmental correlations were.84 and.63 respectively). Conclusions: The findings provide deeper insight into the aetiology of dental anxiety and confirm that while it is strongly linked to treatment‐related pain experiences, this relation is to a considerable degree independent of general negative affectivity/neuroticism. [ABSTRACT FROM AUTHOR]

Objective: Twin pregnancies are associated with increased antepartum and intrapartum risks. Limited multiple embryo transfers are associated with decreased twin birth rates. We aimed to study the effect of 2009 Icelandic regulations on twin birth rates and examine obstetric intervention rates for twin births during the study period. Methods: The study included all births (N = 94 028) in Iceland during 1997–2018. Twin birth rates and obstetric intervention rates were compared over birth year periods using modified Poisson regression adjusted for confounders. Results: An observed decrease in the twin birth rate trend was most notable from 2006 until 2009. Twin birth decreased in 2009–2013 (prevalence ratio [PR] 0.74, 95% confidence interval [CI] 0.64–0.86) and in 2014–2018 (PR 0.74, 95% CI 0.64–0.86) compared with 1997–2002. This decrease was only evident for women aged 30+ years in stratified analysis. Induction of labor rates increased from 26% in 1997–2002 to 44% in 2014–2018 (adjusted rate ratio [ARR] 2.10, 95% CI 1.72–2.57) whereas elective cesarean section (ARR 0.80, 95% CI 0.59–1.07) and urgent cesarean section (ARR 0.79, 95% CI 0.63–1.00) rates appeared to decline. Conclusion: Twin births decreased during the study period. International guidelines published before the Icelandic regulations may have affected twin birth rates in Iceland. Induction of labor rates for twins increased while cesarean section rates decreased. Synopsis: Icelandic embryo transfer regulations may have had a decreasing effect on twin birth rates. Rates of induction of labor increased and cesarean section rates decreased for twins. [ABSTRACT FROM AUTHOR]

Objective: To examine neonatal outcomes at birth among twins conceived spontaneously or by medically assisted reproduction (MAR). Methods: A retrospective study was conducted at a single university teaching hospital on data collected between January 1995 and September 2019. Live twin deliveries at more than 24 weeks of pregnancy were included. The study group consisted of women who conceived by MAR and the controls were spontaneously conceived twins. The study group was further divided into two groups: in vitro fertilization (IVF) and ovulation induction (OI) groups. The primary outcomes were umbilical artery pH less than 7.1 and/or Apgar score less than 7 of any twin 5 min after birth. Results: Overall, 2235 eligible twin gestations were included, corresponding to a total of 4470 live neonates; 1009 (45.1%) conceived by MAR (762 [75.5%] IVF and 247 [24.5%] OI) and 1226 (54.9%) conceived spontaneously. Incidence of the primary outcome was 5.3% and 5.1% in the study and control groups, respectively (P = 0.71). The primary outcome was comparable among the IVF (5%), OI (6.2%), and control (5.1%) groups. The results did not change even after adjusting for demographic and obstetric variables, including mode of delivery, which differed between the groups. Conclusion: Neonatal condition of twin pregnancies at birth among MAR subgroups is similar to spontaneously conceived twins. Synopsis: Incidence of neonatal Apgar score <7 at 5 min and cord artery pH <7.1 is comparable in twins conceived spontaneously or by medically assisted reproduction. [ABSTRACT FROM AUTHOR]

Aims: To evaluate cardiac findings in newborn twins from the general population and investigate if newborn twins may require systematic evaluation of cardiac parameters. Methods: Prospective cohort study of newborns with cardiac evaluation performed during the first month of life. Cardiac findings were compared 1:3 with matched singletons. Results: We included 412 newborn twins (16% monochorionic; 50% boys) and 1236 singletons. Comparing cardiac findings showed twins had an increased prevalence of non‐severe structural heart disease (most common: ventricular septal defects in both groups), thinner left ventricular posterior wall in diastole (LVPWd; 1.82 vs. 1.87 mm, p = 0.02), smaller diameter of the left atrium (10.6 vs. 11.1 mm, p = 0.04), higher heart rate (148 vs. 144 bpm, p = 0.04), more left‐shifted QRS axis (106 vs. 111°, p < 0.001), and lower maximum R‐wave amplitude in V1 (927 vs. 1015 μV, p = 0.02) compared to singletons. After multifactorial adjustment for potential confounders, the effect of twinning on cardiac parameters persisted only for LVPWd (p < 0.05). Conclusion: Despite contemporary surveillance, we found an increased prevalence of non‐severe structural heart disease in a population‐based cohort of newborn twins. However, the effect of twinning on cardiac parameters was modest and generally did not persist after correction for likely confounding factors. [ABSTRACT FROM AUTHOR]

Objective: Eating disorders are associated with subsequent alcohol problems, but it is not known whether this association also extends to broader eating disorder symptoms not captured by clinical diagnoses. We assessed the longitudinal association of broad eating disorder symptoms with alcohol problems in a nationwide twin sample (FinnTwin16). Methods: Finnish women (N = 1905) and men (N = 1449) self‐reported their eating disorder symptoms using the Eating Disorder Inventory‐2 Bulimia, Drive for Thinness, and Body Dissatisfaction subscales at the mean age of 24.4 years in 2000–2003. A subsample of participants also completed items on drive for muscularity, height dissatisfaction, and muscle‐enhancing supplement use. Alcohol problems were assessed 10 years later at the age of 34.1 in 2010–2012 with the Rutgers Alcohol Problem Index. Results: Eating disorder symptoms were associated with later alcohol problems (odds ratio per point increase 1.02–1.18). Bulimia showed stronger associations among men than women (p for interaction.012). Drive for muscularity and height dissatisfaction were also associated with later alcohol problems, but supplement use was not. When accounting for baseline alcohol problems, only Bulimia (among women and men) and Drive for Thinness (among men) were significantly associated with later alcohol problems. Bulimia was also significantly associated with later alcohol problems in within‐twin‐pair analyses among dizygotic twins, but not among monozygotic twins. Discussion: In a longitudinal setting, eating disorder symptoms were associated with later alcohol problems. Bulimic symptoms were a stronger risk factor for men than women. These associations may be attributable to baseline alcohol problems, childhood environment and genetic liability. Public significance: This study found that both young adult women and men with broad eating disorder symptoms are at a higher risk of alcohol‐related problems than those without such symptoms. Men with bulimic symptoms were at a particularly high risk. These findings emphasize the need for better prevention and treatment of disordered eating, body image concerns and alcohol problems for both young adult women and men. [ABSTRACT FROM AUTHOR]

Objectives: To evaluate the outcome of monochorionic diamniotic (MCDA) twins complicated by Type‐II selective fetal growth restriction (sFGR) who underwent fetoscopic laser photocoagulation and to validate a previously proposed subclassification system for Type‐II sFGR in a large multicenter cohort. Methods: This retrospective multicenter cohort study included all MCDA twins complicated by Type‐II sFGR who underwent laser photocoagulation of placental anastomoses at four large tertiary fetal‐care centers between 2006 and 2020. Cases were subclassified according to a recently proposed system based on Doppler evaluation of the ductus venosus (DV) and middle cerebral artery (MCA) into Type‐IIA (normal DV flow and MCA peak systolic velocity (PSV) of the growth‐restricted fetus) or Type‐IIB (absent or reversed flow in the DV during atrial contraction and/or MCA‐PSV ≥ 1.5 multiples of the median of the growth‐restricted fetus). Demographic characteristics and pregnancy outcomes were compared between the groups. Data are presented as mean ± SD or n (%) as appropriate. P‐values < 0.05 were considered statistically significant. Results: A total of 98 patients with MCDA twins met our inclusion criteria, with 56 subclassified as Type IIA and 42 as Type IIB. Demographic characteristics were similar between the groups; however, Type‐IIB cases had a significantly earlier gestational age at diagnosis and at laser surgery, as well as larger intertwin estimated fetal weight discordance, which may be a reflection of disease severity. Postnatal survival of the growth‐restricted fetus to 30 days of age was significantly lower in Type‐IIB compared to Type‐IIA cases (23.8% vs 46.4%; P = 0.034). Conclusions: In MCDA twins complicated by Type‐II sFGR and treated with laser photocoagulation of placental anastomoses, preoperative Doppler assessment of the DV and MCA helped identify a subset of patients at increased risk of demise of the growth‐restricted fetus following intervention. This study provides valuable information for guiding surgical management and patient counseling. © 2023 International Society of Ultrasound in Obstetrics and Gynecology. [ABSTRACT FROM AUTHOR]

Background: Twin studies have demonstrated shared genetic and environmental effects between eating disorders and alcohol involvement in adults and middle adolescents. However, fewer studies have focused on late adolescents or investigated a wide range of eating disorder dimensions and alcohol involvement subscales in both sexes. We examined genetic and environmental correlations among three eating disorder dimensions and two alcohol involvement subscale scores in late adolescent twins using bivariate twin models. Methods: Participants were 3568 female and 2526 male same‐sex twins aged 18 years old from the Child and Adolescent Twin Study in Sweden. The Eating Disorder Inventory‐2 (EDI) assessed the drive for thinness, bulimia, and body dissatisfaction. Alcohol involvement was assessed with the Alcohol Use Disorder Identification Test consumption (AUDIT‐C) and problem (AUDIT‐P) subscales. Results: Only phenotypic and twin correlations in female twins met our threshold for twin modeling. The proportion of total variance for each trait accounted for by additive genetic factors ranged from 0.50 to 0.64 in female twins, with the rest explained by nonshared environmental factors and measurement error. Shared environmental factors played a minimal role in the variance of each trait. The strongest genetic correlation (ra) emerged between EDI bulimia and AUDIT‐P (ra = 0.46, 95% confidence interval: 0.37, 0.55), indicating that the proportion of genetic variance of one trait that was shared with the other trait was 0.21. Nonshared environmental correlations between eating disorder dimensions and alcohol involvement ranged from 0.03 to 0.13. Conclusions: We observed distinct patterns of genetic and environmental effects for co‐occurring eating disorder dimensions and alcohol involvement in female vs. male twins, supporting sex‐specific treatment strategies for late adolescents with comorbid eating disorders and alcohol use disorder. Our findings emphasize the importance of assessing family history of multiple eating disorder dimensions while treating late adolescents with problematic alcohol use, and vice versa, to improve detection and treatment. [ABSTRACT FROM AUTHOR]

Mollusk shells protect the animals that form and inhabit them. They are composites of minerals and organics, with diverse mesostructures, including nacre, prismatic calcite, crossed‐lamellar aragonite, and foliated calcite. Twins, that is, crystals mirror symmetric with respect to their coherent interface, occurring as formation or deformation twins, are observed in all mollusk shell mesostructures but never within calcite prisms. Here, nanotwins and microwins within single calcite prisms are observed in different shells. Using Polarization‐dependent Imaging Contrast (PIC) mapping with 20–60 nm resolution, twins are observed to be 0.2–3 µm thick layers of differently oriented and colored crystals with respect to the main prism crystal. Multiple twins are interspersed with the prism crystal, parallel to one another, and similarly oriented. When comparing images of calcite prisms and twins obtained by PIC mapping and by Electron Back‐Scattered Diffraction (EBSD), the images correspond precisely. All twins are e‐twin types, with 127° angular distance between c‐axes. E‐twins are the most common deformation twins in geologic calcite, as also observed here in Carrara marble. Location of all twins near the outer surface of all shells and e‐twin type both suggest that twins within calcite prisms in mollusk shells result from deformation twinning. [ABSTRACT FROM AUTHOR]

Objective: To compare the neurodevelopmental outcomes of preterm twins at 5½ years by chorionicity of pregnancy. Design: Prospective nationwide population‐based EPIPAGE2 (Etude Epidémiologique sur les Petits Âges Gestationnels) cohort study. Setting: A total of 546 maternity units in France, between March and December 2011. Population: A total of 1126 twins eligible for follow‐up at 5½ years. Methods: The association of chorionicity with outcomes was analysed using multivariate regression models. Main outcome measures: Survival at 5½ years with or without neurodevelopmental disabilities (comprising cerebral palsy, visual, hearing, cognitive deficiency, behavioural difficulties or developmental coordination disorders) were described and compared by chorionicity. Results: Among the 1126 twins eligible for follow‐up at 5½ years, 926 (82.2%) could be evaluated: 228 monochorionic (MC) and 698 dichorionic (DC). Based on chronicity and gestational age of birth, we found no significant differences for severe neonatal morbidity. The rates of moderate/severe neurobehavioral disabilities were similar in infants from DC pregnancies versus infants from MC pregnancies (OR 1.22, 95% CI 0.65–2.28). By gestational age and without twin–twin transfusion syndrome (TTTS), no difference according to chorionicity was found for all neurodevelopmental outcome measures. Conclusions: The neurodevelopmental outcomes among preterm twins at 5½ years is similar, irrespective of chorionicity. Linked article: This article is commented on by R. N. Brown, pp. 1059 in this issue. To view this mini commentary visit https://doi.org/10.1111/1471‐0528.17527. [ABSTRACT FROM AUTHOR]

Objective: To estimate the association of advanced maternal age with pregnancy complications in twin pregnancies and compare it with that observed in singleton pregnancies. Methods: A population‐based retrospective cohort study of all patients with a singleton or twin hospital birth in Ontario, Canada, between 2012 and 2019. The primary outcome was preterm birth (PTB) less than 34 weeks. Pregnancy outcomes were stratified by maternal age groups in twin pregnancies and, separately, in singleton pregnancies. Results: A total of 935 378 patients met the study criteria: 920503 (98.4%) had a singleton pregnancy and 14 875 (1.6%) had twins. In singletons, the rate of PTB less than 34 weeks increased progressively with increasing maternal age and was highest for patients aged 45 years or more (3.4%; adjusted risk ratio [aRR] 1.56, 95% confidence interval [CI] 1.05–2.33). By contrast, in twins, although the rate of PTB less than 34 was highest patients under 20 years of age (25.3%) and was lowest among patients aged 35–39 years (11.7%), the associations between maternal age group and the risk of PTB were not statistically significant in the adjusted analysis. Conclusion: Although the absolute rates of pregnancy complications are higher in twin pregnancies, there are considerable differences in the relationship between maternal age and the risk of certain complications between twin and singleton pregnancies. Synopsis: The relationship between maternal age and the risk of pregnancy complications differs between twin and singleton pregnancies. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the natural evolution of and risk factors for the adverse outcome of monochorionic twins with selective intrauterine growth restriction (sIUGR) under expectant management. Methods: Retrospective study conducted in a single tertiary referral center. The clinical characteristics and neonatal outcomes of 153 patients with sIUGR under expectant management were evaluated, and the risk factors leading to adverse outcomes were explored. Results: Fifty‐one patients (33.3%) showed a changed pattern in umbilical artery Doppler at the last examination, occurring in all types of sIUGR. Compared with type Ia, the gestational age of diagnosis was earlier, the estimated fetal body weight difference at diagnosis was greater, and the rate of severe neonatal complications in both fetuses was significantly higher in type Ib (P < 0.05). Univariate and multivariate logistic regression analyses showed that type II (odds ratio [OR] 5.41, 95% confidence interval [CI] 2.34–12.51; P < 0.001) and type III (OR 9.11, 95% CI 3.02–27.50; P < 0.001) were associated with adverse perinatal outcomes in sIUGR. Conclusion: Type II and III sIUGR are independent risk factors predicting adverse outcomes of sIUGR. Different types of sIUGR could convert to each other. The outcome of type Ib is poorer than that of type Ia. Synopsis: Type II and III are independent risk factors for adverse outcomes of sIUGR while type Ib had a poorer outcome compared with type Ia. [ABSTRACT FROM AUTHOR]

Introduction: The aims of the study were to evaluate perinatal outcome in monochorionic (MC) twins complicated with single intrauterine fetal death, spontaneously vs after fetal therapy, and to assess antenatal events that increase the risk of cerebral injury. Material and methods: Historical cohort study of MC pregnancies with single intrauterine fetal death diagnosed or referred to a tertiary referral hospital (2012–2020). Adverse perinatal outcome included termination of pregnancy, perinatal death, abnormal fetal or neonatal neuroimaging and abnormal neurological development. Results: A total of 68 MC pregnancies with single intrauterine fetal death after 14 weeks of gestation were included. Sixty‐five (95.6%) occurred in complicated MC pregnancies (twin to twin transfusion syndrome: 35/68 [51.5%]; discordant malformation: 13/68 [19.1%], selective intrauterine growth restriction: 10/68 [14.7%], twin reversed arterial perfusion sequence: 5/68 [7.3%] and cord entanglement in monoamniotic twins: 2/68 [2.94%]). In 52 cases (76.5%) single intrauterine fetal demise occurred after fetal therapy and in 16 (23.5%) occurred spontaneously. Cerebral damage included 14/68 cases (20.6%): 6/68 cases (8.82%) were prenatal lesions and 8/68 cases (11.8%) were postnatal. Risk of cerebral damage tended to be higher in the spontaneous death group (6/16, 37.5%) compared to the therapy‐group (8/52, 15.38%) (p = 0.07). The risk increased with gestational age at intrauterine death (OR 1.21, 95% CI: 1.04–1.41, p = 0.014) and was higher in those surviving co‐twins who developed anemia (OR 9.27, 95% CI: 1.50–57.12, p = 0.016). Pregnancies complicated with selective intrauterine growth restriction tended to be at higher risk for neurological damage (OR 2.85, 95% CI: 0.68–11.85, p = 0.15). Preterm birth rate (<37 weeks of pregnancy) was 61.7% (37/60). Seven of eight postnatal cerebral lesions (87.5%) were related to extreme prematurity. Overall perinatal survival rate was 88.3% (57/68) and 7% (4/57) of children had an abnormal neurological outcome. Conclusions: Risk of cerebral damage in single intrauterine fetal death is especially high when it occurs spontaneously. Gestational age at single intrauterine fetal death, selective intrauterine growth restriction and anemia of the surviving co‐twin are the main predictors for prenatal lesions and might be useful in parent counseling. Abnormal postnatal neurological outcome is closely related to extreme prematurity. [ABSTRACT FROM AUTHOR]

Introduction: Multiple gestations are a risk factor for most pregnancy complications. The current study aimed to study whether offspring born after twin pregnancies are at increased risk for long‐term health complications. Material and methods: A retrospective cohort study was conducted in a large medical center, including all offspring born between the years 1991–2021, which were followed‐up until 18 years of age. Hospital‐based diagnoses of the offspring were categorized into main groups of morbidities: cardiac, respiratory, infectious, neurological, malignancy, and metabolic. Incidence of hospitalization with diagnoses from each main group was compared between twins and singletons, as well as time to first hospitalization. Cox proportional hazard models were used to study the association between twins vs singletons and hospitalizations by grouped morbidities, while adjusting for maternal age, ethnicity and gender, besides maternal recurrence in the cohort. Results: A total of 369 478 offspring were included in the analysis; of these 11 986 (3.2%) were twins and 357 492 (96.8%) were singletons. Twins were more likely to be delivered preterm (odds ratio = 17.65, 95% CI: 16.74–18.60), by cesarean delivery and following infertility treatments. Incidence of hospitalizations with all morbidity groups was slightly, some significantly, higher among twins, including cardiac: 1.9% vs 1.5%, respiratory; 8.4% vs 7.1%, neurological: 7.7% vs 7.4%, infectious: 26.0% vs 24.1%, and malignancies: 0.7% vs 0.4%. The risk remained higher in the multivariable analyses (adjusted hazard ratios ranging between 1.09–1.75). When stratifying by gestational age at delivery, the risk for most morbidities was lower among twins vs singletons born in similar gestational ages. Conclusions: Twins as compared to singletons are at increased risk for most morbidities due to their risk of being born earlier. [ABSTRACT FROM AUTHOR]

Genealogical samples that couple dental data and documented relatedness information provide unique opportunities to examine the biological foundations of tooth variation. Over the past century, these resources have been critical for examining the various factors that influence dental phenotypes—the same traits that anthropologists regularly apply to reconstructions of past phenomena. Genealogical samples are uniquely suited to test long‐standing assumptions underlying bioanthropological practice, for example, biodistance and phylogenetic analysis, which commonly reference aspects of tooth size and form as proxies for latent genetic information. This article provides an overview of published genealogical research, with a focus on the practical implications of quantitative genetic and environmental studies of (non)human primate dentitions. To highlight the utility of genealogical samples for understanding the influence of specific non‐genetic factors on dental characters, we also present novel data on gestational hormone effects in opposite‐sex dizygotic twin pairs as a test of the twin testosterone transfer (TTT) hypothesis. This article discusses fruitful next steps in genealogical dental research, as well as important ethical considerations surrounding the use of associated datasets, which are sensitive in nature. As we forge ahead in an age of phenomics, genealogical samples are likely to play a key role in generating comprehensive genotype–phenotype maps of the dentition and in refining bioanthropological methods. [ABSTRACT FROM AUTHOR]

Identifying metabolic biomarkers of frailty, an age‐related state of physiological decline, is important for understanding its metabolic underpinnings and developing preventive strategies. Here, we systematically examined 168 nuclear magnetic resonance‐based metabolomic biomarkers and 32 clinical biomarkers for their associations with frailty. In up to 90,573 UK Biobank participants, we identified 59 biomarkers robustly and independently associated with the frailty index (FI). Of these, 34 associations were replicated in the Swedish TwinGene study (n = 11,025) and the Finnish Health 2000 Survey (n = 6073). Using two‐sample Mendelian randomization, we showed that the genetically predicted level of glycoprotein acetyls, an inflammatory marker, was statistically significantly associated with an increased FI (β per SD increase = 0.37%, 95% confidence interval: 0.12–0.61). Creatinine and several lipoprotein lipids were also associated with increased FI, yet their effects were mostly driven by kidney and cardiometabolic diseases, respectively. Our findings provide new insights into the causal effects of metabolites on frailty and highlight the role of chronic inflammation underlying frailty development. [ABSTRACT FROM AUTHOR]

Aim: We compared milk volumes, skin‐to‐skin contact and breastfeeding by the mothers of very preterm twins and singleton infants born at 28–32 weeks of gestation. Methods: This Norwegian longitudinal prospective comparative study was carried out in two neonatal intensive care units: one with single family rooms and one open bay unit. It comprised 49 singleton infants, 28 twins and their mothers. The mothers' milk volume and direct breastfeeding were recorded from birth until 4 months' of corrected age. They also answered the breastfeeding self‐efficacy scale and skin‐to‐skin contact was recorded. Results: The mothers of preterm twins produced doubled the volume of expressed milk at day 14, compared to the mothers of singletons (mean 816 ± 430 mL vs. 482 ± 372 mL, p < 0.05) and this difference was still sustained at 34 + 0 weeks/days (p < 0.02). Mothers of twins had their first breastfeeding attempt later than mothers of singletons (median of 133 h compared to 56 (p < 0.002). Preterm twins received less daily skin‐to‐skin contact (mean 157 ± 66 min each vs. 244 ± 109) (p < 0.001). There were no differences in receiving mother's own milk, exclusively direct breastfeeding or perceived breastfeeding self‐efficacy. Conclusion: Breastfeeding was initiated as successfully in preterm twins as singletons as the mothers' milk production doubled. [ABSTRACT FROM AUTHOR]

Summary: Background: Being born with intrauterine growth restriction (IUGR) was associated with subsequent health issues later in life. However, the underlying role of adipokines in IUGR is unknown. Objectives: To measure the adiponectin and leptin concentrations in the cord blood of monochorionic (MC) twins with selective IUGR (sIUGR) and evaluate their associations with childhood growth trajectories. Methods: Cord blood samples were collected from 22 pairs of MC twins with sIUGR and 20 pairs of normal MC twins. Adiponectin and leptin concentrations in cord blood were determined by ELISA. Data regarding perinatal outcomes and infantile growth trajectories from birth to 24 months were obtained. Results: Only cord blood adiponectin concentrations were associated with IUGR (β −1.51, 95% CI −2.45, −0.57, p = 0.002), and cord blood leptin concentrations were significantly lower in sIUGR twins compared to normal twins (2.8 ± 1.6 vs. 6.4 ± 3.0, p < 0.001). Adiponectin concentrations were negatively associated with height increments from birth to 6 months (β −0.28, 95% CI −0.51, −0.06, p = 0.015). Leptin concentrations were negatively associated with weight at 6 and 24 months (β −0.12 95% CI −0.22, −0.02, p = 0.002; β −0.18 95% CI −0.33, −0.03, p = 0.019) and weight and height increments from birth to 6 months (β −0.17 95% CI −0.29, −0.06, p = 0.020; β −0.40 95% CI −0.81, −0.01, p = 0.037). Conclusion: Cord blood adiponectin concentrations were negatively associated with IUGR but did not predict childhood growth. Cord blood leptin concentrations were inversely associated with weight and height increments in the first 6 months. [ABSTRACT FROM AUTHOR]

The ability to perceive approximate numerosity is present in many animal species, and emerges early in human infants. Later in life, it is moderately heritable and associated with mathematical abilities, but the etiology of the Approximate Number System (ANS) and its degree of independence from other cognitive abilities in infancy is unknown. Here, we assessed the phenotypic specificity as well as the influence of genetic and environmental factors on the ANS in a sample of 5‐month‐old twins (N = 514). We found a small‐to‐moderate but statistically significant effect of genetic factors on ANS acuity (heritability = 0.18, 95% CI: 0.02, 0.33), but only when differences in numerosity were relatively large (1:4 ratio). Non‐verbal ability assessed with the Mullen Scales of Early Learning (MSEL) was found to be heritable (0.47; 95% CI: 0.34, 0.57) and the phenotypic association between ANS acuity and non‐verbal ability performance was close to zero. Similarly, we found no association between ANS acuity and general attention during the task. An unexpected weak but statistically significant negative association between ANS acuity and scores on the receptive language scale of the MSEL was found. These results suggest that early ANS function may be largely independent from other aspects of non‐verbal development. Further, variability in ANS in infancy seems to, to some extent, reflect genotypic differences in the population. Highlights: Assessing 514 infant twins with eye tracking, we found that infants' sense of approximate numerosity is heritable and not positively associated with concurrent attentional, cognitive or motor abilities.These results have implications for our understanding of development of mathematical ability and the link between cognitive abilities early in postnatal life. [ABSTRACT FROM AUTHOR]

Gypsum twins are frequently observed in nature, triggered by a wide array of impurities that are present in their depositional environments and that may exert a critical role in the selection of different twin laws. Identifying the impurities able to promote the selection of specific twin laws has relevance for geological studies aimed at interpreting the gypsum depositional environments in ancient and modern deposits. Here, the effect of calcium carbonate (CaCO3) on gypsum (CaSO4·2H2O) growth morphology has been investigated by performing temperature‐controlled laboratory experiments with and without the addition of carbonate ions. The precipitation of twinned gypsum crystals has been achieved experimentally (101 contact twin law) by adding carbonate to the solution, and the involvement of rapidcreekite (Ca2SO4CO3·4H2O) in selecting the 101 gypsum contact twin law was supported, suggesting an epitaxial mechanism. Moreover, the occurrence of 101 gypsum contact twins in nature has been suggested by comparing the natural gypsum twin morphologies observed in evaporitic environments with those obtained in experiments. Finally, both orientations of the primary fluid inclusions (of the negative crystal shape) with respect to the twin plane and the main elongation of sub‐crystals that form the twin are proposed as a fast and useful method (especially in geological samples) to distinguish between the 100 and 101 twin laws. The results of this study provide new insights into the mineralogical implications of twinned gypsum crystals and their potential as a tool to better understand natural gypsum deposits. [ABSTRACT FROM AUTHOR]