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Objective To assess whether the reported excess of large for gestational age ( LGA) neonates in pre-eclamptic women delivering at term is attributable to maternal obesity. Design, setting and population Population-based observational study including 77 294 singleton pregnancies registered in the Medical Birth Registry of Norway between 2007 and 2010. Methods Comparison of birthweight percentiles and z-scores between women with and without pre-eclampsia. Main outcome measures Odds ratio ( OR) of LGA and z-scores of birthweight in relation to pre-eclampsia. Results Pre-eclamptic women delivering at term had increased risk of having LGA neonates. Unadjusted ORs with 95% confidence interval (95% CI) of LGA above the 90th and 95th birthweight centiles were 1.4, 95% CI 1.2-1.6 and 1.6, 95% CI 1.3-1.9, respectively. The excess of LGA persisted after including gestational diabetes and diabetes types 1 and 2 in a multivariate analysis (corresponding ORs 1.3, 95% CI 1.1-1.5 and 1.4, 95% CI 1.2-1.7), but disappeared after adjusting for maternal prepregnant body mass index ( ORs 1.1, 95% CI 0.9-1.2 and 1.1, 95% CI 0.9-1.3). Conclusions This study suggests accelerated fetal growth in a subset of pre-eclamptic women delivering at term. The excess of LGA neonates is attributable to maternal obesity among pre-eclamptic women delivering at term. The maternal obesity epidemic may lead to an increased prevalence of both pre-eclampsia and LGA neonates among women delivering at term. [ABSTRACT FROM AUTHOR]

Objective To investigate the aggregation of obstetric anal sphincter injuries ( OASIS) in relatives. Design Population-based cohort study. Setting The Medical Birth Registry of Norway from 1967 to 2008. Population All singleton, vertex-presenting infants weighing 500 g or more. Through linkage by national identification numbers, 393 856 mother-daughter pairs, 264 675 mother-son pairs, 134 889 mothers whose sisters later became mothers, 132 742 fathers whose brothers later became fathers, 131 702 mothers whose brothers later became fathers and 88 557 fathers whose sisters later became mothers were provided. Methods Comparison of women with and without a history of OASIS in their relatives. Main outcome measure Relative risk of OASIS after a previous OASIS in the family. Results The risk of OASIS was increased if the woman's mother or sister had OASIS in a delivery ( aRR 1.9, 95% CI 1.6-2.3; aRR 1.7, 95% CI 1.6-1.7, respectively). If OASIS occurred in one brother's partner at delivery, the risk of OASIS in the next brother's partner was modestly increased ( aRR 1.2, 95% CI 1.1-1.4). If OASIS occurred in one sister at delivery, the risk of OASIS in the brother's partner was also increased a little ( aRR 1.2, 95% CI 1.1-1.4). However, there was no excess occurrence in sisters whose brothers' partners had previously had OASIS ( aRR 1.1, 95% CI 0.9-1.3). Conclusions There appears to be increased familial aggregation of OASIS. These risks are stronger through the maternal rather than the paternal line of transmission, suggesting a strong genetic role that shapes aggregation of OASIS within families. These observations must be cautiously interpreted because of bias from unmeasured confounding factors may have impacted the findings. [ABSTRACT FROM AUTHOR]

Objective: To assess parity in women with chronic inflammatory arthritides (CIA) childless at time of diagnosis. Methods: Patients were selected from the Norwegian Disease-Modifying Anti-Rheumatic Drug (NOR-DMARD) registry. Each patient was matched by year of birth with 100 reference women from the Norwegian Population Registry. Data linkage for patients and references with the Medical Birth Registry of Norway (MBRN) identified all offspring until time of linkage (October 2007). Patients and corresponding references childless at the time of diagnosis were included in the analyses. Kaplan-Meier curves visualized the proportion of childless women and were compared by a log rank test. Results: In all, 156 rheumatoid arthritis (RA), 107 other chronic arthritides (OCA), and 75 juvenile idiopathic arthritis (JIA) patients were childless at time of diagnosis. At the time of data linkage, the proportions (%) of childless RA/OCA/JIA patients versus references were 61.5/62.6/57.3 versus 46.9/42.9/41.0, respectively, all differences statistically significant. The log rank test showed lower parity in all diagnostic groups compared with references (p < 0.001 for RA and OCA and p = 0.002 for JIA). No difference in parity was observed between RA and OCA patients, but both diagnostic groups had lower parity than JIA patients (p = 0.001). Disease characteristics were similar between childless and fertile patients. Conclusions: Reduced parity was observed in all diagnostic groups compared with references. RA and OCA patients had lower parity than JIA patients, indicating that having the disease as a young adult may influence parity more than having the disease in childhood. [ABSTRACT FROM AUTHOR]

Please cite this paper as: Baghestan E, Irgens L, Børdahl P, Rasmussen S. Risk of recurrence and subsequent delivery after obstetric anal sphincter injuries. BJOG 2012;119:62-69. Objective To investigate the recurrence risk, the likelihood of having further deliveries and mode of delivery after third to fourth degree obstetric anal sphincter injuries (OASIS). Design Population-based cohort study. Setting The Medical Birth Registry of Norway. Population A cohort of 828 864 mothers with singleton, vertex-presenting infants, weighing 500 g or more, during the period 1967-2004. Methods Comparison of women with and without a history of OASIS with respect to the occurrence of OASIS, subsequent delivery rate and planned caesarean rate. Main outcome measures OASIS in second and third deliveries, subsequent delivery rate and mode of delivery. Results Adjusted odds ratios of the recurrence of OASIS in women with a history of OASIS in the first, and in both the first and second deliveries, were 4.2 (95% CI 3.9-4.5; 5.6%) and 10.6 (95% CI 6.2-18.1; 9.5%), respectively, relative to women without a history of OASIS. Instrumental deliveries, in particular forceps deliveries, birthweights of 3500 g or more and large maternity units were associated with a recurrence of OASIS. Instrumental delivery did not further increase the excess recurrence risk associated with high birthweight. A man who fathered a child whose delivery was complicated by OASIS was more likely to father another child whose delivery was complicated by OASIS in another woman who gave birth in the same maternity unit (adjusted OR 2.1; 95% CI 1.2-3.7; 5.6%). However, if the deliveries took place in different maternity units, the recurrence risk was not significantly increased (OR 1.3; 95% CI 0.8-2.1; 4.4%). The subsequent delivery rate was not different in women with and without previous OASIS, whereas women with a previous OASIS were more often scheduled to caesarean delivery. Conclusion Recurrence risks in second and third deliveries were high. A history of OASIS had little or no impact on the rates of subsequent deliveries. Women with previous OASIS were delivered more frequently by planned caesarean delivery. [ABSTRACT FROM AUTHOR]

Objective: The objective of this study was to analyze whether maternal negative affectivity assessed in pregnancy is related with subsequent infant food choices.Design: The study design was a cohort study.Subjects: The subjects were mothers (N=37 919) and their infants participating in the Norwegian Mother and Child Cohort Study conducted by the Norwegian Institute of Public Health.Measurements: Maternal negative affectivity assessed prepartum (Hopkins Symptom Checklist 5 (SCL-5) at weeks 17 and 30 of pregnancy), introduction of solid foods by month 3 and feeding of sweet drinks by month 6 (by the reports of the mothers) were analyzed.Results: Mothers with higher negative affectivity were 64% more likely (95% confidence interval 1.5-1.8) to feed sweet drinks by month 6, and 79% more likely (95% confidence interval 1.6-2.0) to introduce solid foods by month 3. These odds decreased to 41 and 30%, respectively, after adjusting for mother's age, body mass index (BMI) and education.Conclusion: The maternal trait of negative affectivity is an independent predictor of infant feeding practices that may be related with childhood weight gain, overweight and obesity. [ABSTRACT FROM AUTHOR]

BACKGROUND: The hypothesis of intrauterine origin of adult disease is debated. We tested whether intrauterine growth restriction is associated with later kidney function. STUDY DESIGN: Prospective cohort study. SETTING & PARTICIPANTS: 7,457 Norwegian adults aged 20 to 30 years participating in the population-based Nord Trøndelag Health Study (1995-1997) with data for birth weight, gestational age, and maternal and perinatal risk factors registered at the Medical Birth Registry of Norway. PREDICTOR: Birth weight expressed as an SD score (SDS) to adjust for gestational age and sex. Subjects with a birth weight SDS less than -2.0, -2.0 to -1.3, and -1.3 to 1.3 were defined as very small, small, and appropriate for gestational age, corresponding to less than the 3rd, 3rd to 10th, and 10th to 90th percentiles, respectively. OUTCOME & MEASUREMENTS: Kidney function estimated using the Cockcroft-Gault and isotope dilution mass spectrometry-traceable 4-variable Modification of Diet in Renal Disease (MDRD) Study equation. Values less than the sex-specific 10th percentile were defined as low-normal kidney function. RESULTS: Compared with men with birth weight appropriate for gestational age (n = 2,755), odds ratios for low-normal creatinine clearance (<100 mL/min) were 1.66 (95% confidence interval [CI], 1.16 to 2.37) if small for gestational age (n = 261) and 2.40 (95% CI, 1.46 to 3.94) if very small for gestational age (n = 101). Kidney function estimated using the MDRD Study equation gave similar results. Women (n = 3,126, 283, and 112, respectively) had odds ratios of 1.65 (95% CI, 1.17 to 2.35) and 2.00 (95% CI, 1.21 to 3.29) for low-normal creatinine clearance (<80 mL/min), whereas the association was not significant using the MDRD Study equation. Using linear regression, creatinine clearance decreased by 4.0 mL/min (95% CI, 3.3 to 4.6) in men and 2.9 mL/min (95% CI, 2.2 to 3.5) in women per 1-SDS decrease. Adjusting for possible confounders did not influence results. LIMITATIONS: Selection bias could be a problem because the participation rate was 49%, but there were no statistically significant differences between participants and nonparticipants regarding maternal and perinatal characteristics. Adjusting kidney function for body size can be a special problem in people with intrauterine growth restriction. CONCLUSIONS: Although effects were still small in young adulthood, intrauterine growth restriction was significantly associated with low-normal kidney function. The effect was weaker and less consistent in women compared with men. Copyright © 2008 National Kidney Foundation, Inc. [ABSTRACT FROM AUTHOR]

Familial correlations in birth weight and gestational age have been explained by fetal and maternal genetic factors, mainly in studies on offspring of twins. The aim of the present intergenerational study was to estimate and compare fetal and maternal genetic effects and shared sibling environmental effects on birth weight and gestational age and also on crown-heel length and head circumference. The authors used path analysis and maximum likelihood principles to estimate these effects and, at the same time, to adjust for covariates. Parent-offspring data were obtained from the Medical Birth Registry of Norway from 1967 to 2004. For the analysis of birth weight and crown-heel length, 101,748 families were included; for gestational age, 91,617 families; and for head circumference, 77,044 families. Assuming no cultural transmission and random mating, the authors found that fetal genetic factors explained 31% of the normal variation in birth weight and birth length, 27% of the variation in head circumference, and 11% of the variation in gestational age. Maternal genetic factors explained 22% of the variation in birth weight, 19% of the variation in birth length and head circumference, and 14% of the variation in gestational age. Relative to the proportion of explained variation, fetal genes were most important for birth length and head circumference. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the effects of early- and late-onset preeclampsia on fetal growth and body proportion.Methods: This was a population-based study based on records of 672,130 pregnancies from the Medical Birth Registry of Norway during 1967-1998. Women with a prior birth, multiple births, those without valid data on the last menstrual period or newborn's crown-heel length, and chronic maternal disease were excluded.Results: In newborns of women with preeclampsia, mean birth weight, crown-heel length, and ponderal index were 4.4%, 0.8%, and 2.6% lower than in births without preeclampsia, respectively. In preterm births, mean differences in birth weight ranged from -11% to -23% against near-equal birth weights in term births. Mean differences in crown-heel length and ponderal index ranged from -1% to -5% and from -5% to -10% before term, respectively. In late preeclampsia, rates of birth weight and crown-heel length above the 90th and 97.5th percentiles and ponderal index above the 97.5th percentile were slightly but significantly higher than in term births without preeclampsia (odds ratios = 1.1-1.5). However, infants born to mothers with preterm preeclampsia were less likely to be heavy, long, or with high ponderal index for gestational age (odds ratios = 0.4-0.6).Conclusion: Our results support the hypothesis that preeclampsia is an etiologically heterogeneous disorder that occurs in at least two subsets, one with normal or enhanced placental function, and another involving placental dysfunction and fetal growth restriction, often with asymmetric fetal body proportion, reduced fetal length, and preterm delivery. In future studies, distinguishing between the two subtypes may be important. [ABSTRACT FROM AUTHOR]

Background: From the early 1970s to the early 1990s, there was a significant rise in the incidence of sudden infant death syndrome (SIDS) in Scandinavia. Following the risk reducing campaign, the incidence has fallen to about the same level as in 1973.Aims: To identify the changes that have occurred in the epidemiology of SIDS.Methods: We compared the Swedish part of the Nordic Epidemiological SIDS Study (NESS), covering the years 1992-1995, with two earlier, descriptive studies during this period. To assess the changing effects of risk factors, we analysed data from the Medical Birth Registry of Sweden, covering the years 1973-1996.Results: There was a predominance of deaths during weekends in the 1970s and 1990s. The seasonal variation was most notable in the 1980s. The proportion of young mothers decreased from 14% to 5%. Cohabitation (living with the biological father) was as frequent in the 1990s as in the 1970s. The prevalence of high parity, admissions to neonatal wards, low birth weight, prematurity, and multiple pregnancies were all increased in the 1990s compared to the 1970s. No significant change in the prevalence of previous apparent life threatening events was found. Deaths occurring in cars diminished from 10% to below 2%. In the data from the Medical Birth Registry of Sweden, there were significantly increased odds ratios after the risk reducing campaign of the risk factors smoking during early pregnancy and preterm birth. We could find no increased effects of maternal age, parity, or being small for gestational age over time. The rate of deaths at weekends remained increased; the median age at death fell from 90 to 60 days. Seasonal variation was less notable in the periods of low incidence. [ABSTRACT FROM AUTHOR]

The objective was to study living conditions of infants and their families in Scandinavia in the 1990s and to assess similarities and differences among the three Scandinavian countries. The emphasis is on health and normality rather than on diseases and other deviations from well-being. The subjects are the 869 controls in the Nordic Epidemiological SIDS study carried out between 1 September 1992 and 31 August 1995 in Norway, Denmark and Sweden. The controls were matched with the 244 SIDS cases for sex, age and maternity hospital. Parents of the SIDS cases and the controls filled in the same questionnaire on family, pregnancy, delivery, the neonatal and the post-perinatal period. The most striking findings were that 99% of the mothers went to regular maternity controls, 97% to well-baby clinics and 84% breastfed exclusively. On the other hand, 11% drank alcohol more than once a month during pregnancy and 29% smoked during pregnancy. Compared to official statistics, to the extent they exist, the differences were small. The material contains valuable information on normal infant care in Scandinavia in the 1990s. Living conditions of infants in Scandinavia are similar in the three countries. Differences exist, but only to a small extent. [ABSTRACT FROM AUTHOR]

Objective: To assess whether alcohol and caffeine are independent risk factors for sudden infant death syndrome (SIDS).Materials and Methods: Analyses based on data from the Nordic epidemiological SIDS study, a case control study in which all parents of SIDS victims in the Nordic countries from 1 September 1992 to 31 August 1995 were invited to participate with parents of four controls, matched for sex and age at death. Odds ratios (ORs) were calculated by conditional logistic regression analysis.Results: The crude ORs for caffeine consumption > 800 mg/24 hours both during and after pregnancy were significantly raised: 3.9 (95% confidence interval (CI), 1.9 to 8.1) and 3.1 (95% CI, 1.5 to 6.3), respectively. However, after adjustment for maternal smoking in 1st trimester, maternal age, education and parity, no significant effect of caffeine during or after pregnancy remained. For maternal or paternal alcohol use, no significant risk increase was found after adjusting for social variables, except for heavy postnatal intake of alcohol by the mother, where the risk was significantly increased.Conclusions: Caffeine during or after pregnancy was not found to be an independent risk factor for SIDS after adjustment for maternal age, education, parity, and smoking during pregnancy. Heavy postnatal but not prenatal intake of alcohol by the mother increased the risk. [ABSTRACT FROM AUTHOR]

To explore the association between smoking and breastfeeding, we obtained data from a retrospective questionnaire-based national survey comprising a random sample (n = 34799) of all mothers giving birth in Norway 1970-91. Variables studied were postpartum smoking habits for both parents, duration of breastfeeding, infant's year of birth and parental age. The response rate was 70% (n = 24438). During the study period, the maternal postpartum smoking prevalence decreased from 38% to 26%. The proportion breastfeeding at 6 months increased from 15% to 44% among smokers, and from 30% to 72% among non-smokers. In spite of a considerable increase in breastfeeding both among smokers and non-smokers, the proportion of breastfeeding, non-smoking women at 6 months was twice that of smoking women during the whole period. Furthermore, the duration of breastfeeding was shorter among young mothers and when the fathers were smoking. There was epidemiological evidence that the effect on breastfeeding of smoking might represent both biological and social mechanisms. [ABSTRACT FROM AUTHOR]

Aim: To establish whether smoking is an independent risk factor for sudden infant death syndrome (SIDS), if the effect is mainly due to prenatal or postnatal smoking, and the effect of smoking cessation.Methods: The analyses were based on data from the Nordic epidemiological SIDS study, a case-control study with 244 cases and 869 controls. Odds ratios were computed by conditional logistic regression analysis.Results: Smoking emerged as an independent risk factor for SIDS, and the effect was mainly mediated through maternal smoking in pregnancy (crude odds ratio 4.0 (95% confidence interval 2.9 to 5.6)). Maternal smoking showed a marked dose-response relation. There was no effect of paternal smoking if the mother did not smoke. Stopping or even reducing smoking was beneficial. SIDS cases exposed to tobacco smoke were breast fed for a shorter time than non-exposed cases, and feeding difficulties were also more common.Conclusions: Smoking is an independent risk factor for SIDS and is mainly mediated through maternal smoking during pregnancy. Stopping smoking or smoking less may be beneficial in reducing the risk of SIDS. [ABSTRACT FROM AUTHOR]

Aims: To assess the effects of breast feeding habits on sudden infant death syndrome (SIDS).Methods: The analyses are based on data from the Nordic Epidemiological SIDS Study, a case-control study in which parents of SIDS victims in the Scandinavian countries between 1 September 1992 and 31 August 1995 were invited to participate, each with parents of four matched controls. The odds ratios presented were computed by conditional logistic regression analysis.Results: After adjustment for smoking during pregnancy, paternal employment, sleeping position, and age of the infant, the adjusted odds ratio (95% CI) was 5.1 (2.3 to 11.2) if the infant was exclusively breast fed for less than four weeks, 3.7 (1.6 to 8.4) for 4-7 weeks, 1.6 (0.7 to 3.6) for 8-11 weeks, and 2.8 (1.2 to 6.8) for 12-15 weeks, with exclusive breast feeding over 16 weeks as the reference. Mixed feeding in the first week post partum did not increase the risk.Conclusions: The study is supportive of a weak relation between breast feeding and SIDS reduction. [ABSTRACT FROM AUTHOR]

A letter to the editor regarding the risk of pre-eclampsia due to maternal obesity.

Background: Unexplained antepartum stillbirth and sudden infant death syndrome (SIDS) are major contributors to perinatal and infant mortality in the western world. A relation between them has been suggested. As an equivalent of SIDS, only cases validated by post mortem examination are diagnosed as sudden intrauterine unexplained death (SIUD).Objective: To test the hypothesis that SIDS and SIUD have common risk factors.Methods: Registration comprised all stillbirths in Oslo and all infant deaths in Oslo and the neighbouring county, Akershus, Norway during 1986-1995. Seventy six cases of SIUD and 78 of SIDS were found, along with 582 random controls surviving infancy, all singletons. Odds ratios were obtained by multiple logistic regression analysis.Results: Whereas SIUD was associated with high maternal age, overweight/obesity, smoking, and low education, SIDS was associated with low maternal age, smoking, male sex, multiparity, proteinuria during pregnancy, and fundal height exceeding +2 SD. Thus the effects of maternal age were opposite in SIUD and SIDS (adjusted odds ratio 1.39 (95% confidence interval 1.17 to 1.66) per year, p < 0.0005). Heavy smoking, male sex, and a multiparous mother was less likely in SIUD than in SIDS (0.22 (0.06 to 0.83), 0.22 (0.07 to 0.78), and 0.03 (<0.01 to 0.17) respectively). Overweight/obesity and low fundal height were more common in SIUD than in SIDS (7.45 (1.49 to 37.3) and 13.8 (1.56 to 122) respectively).Conclusions: The differences in risk factors do not support the hypothesis that SIDS and SIUD have similar determinants in maternal or fetal characteristics detectable by basic antenatal care. [ABSTRACT FROM AUTHOR]

The aim of the study was to investigate the effect of infection on sudden infant death syndrome (SIDS) and to analyse whether modifiable risk factors of SIDS, prone sleeping, covered head and smoking act as effect modifiers. In a consecutive multicentre case-control study of SIDS in Denmark, Norway and Sweden, questionnaires on potential risk factors for SIDS were completed by parents of SIDS victims, and for at least two controls matched for gender, age and place of birth. All SIDS cases were verified by an autopsy. The study comprised 244 SIDS cases and 869 controls, analysed by conditional logistic regression. Significantly more cases than controls presenting symptoms of infectious diseases during the last week and/or last day were treated with antibiotics and had been seen by a physician. The finding is consistent with the hypothesis of an infectious mechanism in SIDS induced by local microorganism growth and toxin or cytokine production, and also adds further support to a possible association between infection and SIDS by loss of protective mechanisms, such as arousal. The risk of SIDS among infants with the combined presence of infectious symptoms and either of the other modfiable risk factors, prone sleeping, head covered or parental smoking, was far greater than the sum of each individual factor. These risk factors thus modify the dangerousness of infection in infancy. [ABSTRACT FROM AUTHOR]

In order to investigate the extent to which musculoskeletal sickness absence was influenced by a range of circumstances concerning family background and health in early life, we established a register-based cohort of all live-born in Norway between 1967 and 1976. Personal data on parental factors and health early in life were recorded prospectively from birth onward in the Medical Birth Registry of Norway, the National Insurance Administration, Statistics Norway, and the Central Population Register. We collected data in the National Insurance Administration on the first spell of medically certified long-term (>16 days) musculoskeletal (International Classification of Primary Care group L) sickness absence in 2000-2003 among 378, 356 participants who were considered to be at risk of sickness absence on January 1st, 2000. The 4-year musculoskeletal absence risk was 0.264 for women and 0.156 for men. Parental education level was associated with musculoskeletal sickness absence, with increasing adjusted relative risks by decreasing educational level for both genders. Associations with other early determinants (birth weight, childhood disease, parental survival, parental disability, parental income, and parental marital status) were all close to unity. Parental education level attributed 36% (95% confidence interval 33-38) to the population risk for women and 67% (64-70) for men. The parental education association was partly mediated through own educational attainment, which was strongly associated with musculoskeletal sickness absence in itself. Our data suggest that mechanisms acting early in life could influence later risk of musculoskeletal sickness absence. [ABSTRACT FROM AUTHOR]

Background: Socioeconomic (SE) inequalities have been observed in a number of adverse outcomes of pregnancy and many of the risk factors for such outcomes are associated with a low SE level. However, SE inequalities persist even after adjustment for these risk factors. Less well-off women are more vulnerable, but may also get less adequate health services. The objective of the present study was to assess possible associations between SE conditions in terms of maternal education as well as ethnic background and obstetric care., Methods: A population-based national cohort study from the Medical Birth Registry of Norway. The study population comprised 2 305 780 births from the observation period 1967-2009. Multilevel analysis was used because of the hierarchical structure of the data. Outcome variables included induction of labour, epidural analgesia, caesarean section, neonatal intensive care and perinatal death., Results: While medical interventions in the 1970s were employed less frequently in women of short education and non-western immigrants, this difference was eliminated or even reversed towards the end of the observation period. However, an excess perinatal mortality in both the short-educated [adjusted relative risk (aRR) = 2.49] and the non-western immigrant groups (aRR = 1.75) remained and may indicate increasing health problems in these groups., Conclusion: Even though our study suggests a fair and favourable development during the last decades in the distribution across SE groups of obstetric health services, the results suggest that the needs for obstetric care have increased in vulnerable groups, requiring a closer follow-up., (© The Author(s) 2020. Published by Oxford University Press on behalf of the European Public Health Association.)

Introduction: In pregnancies after a previous cesarean section (CS), a planned repeat CS delivery has been associated with excess risk of adverse outcome. However, also the alternative, a trial of labor after CS (TOLAC), has been associated with excess risks. A TOLAC failure, involving a non-planned CS, carries the highest risk of adverse outcome and a vaginal delivery the lowest. Thus, the decision regarding delivery mode is pivotal in clinical handling of these pregnancies. However, even with a high TOLAC rate, as seen in Norway, repeat CSs are regularly performed for no apparent medical reason. The objective of the present study was to assess to which extent demographic, socioeconomic, and health system factors are determinants of TOLAC and TOLAC failure in low risk pregnancies, and whether any effects observed changed with time., Materials and Methods: The study group comprised 24 645 second deliveries (1989-2014) after a first delivery CS. Thus, none of the women had prior vaginal deliveries or more than one CS. Included pregnancies were low risk, cephalic, single, and had gestational age ≥ 37 weeks. Data were obtained from the Medical Birth Registry of Norway (MBRN). The exposure variables were (second delivery) maternal age, length of maternal education, maternal country of origin, size of the delivery unit, health region (South-East, West, Mid, North), and maternal county of residence. The outcomes were TOLAC and TOLAC failure, as rates (%), relative risk (RR) and relative risk adjusted (ARR). Changes in determinant effects over time were assessed by comparing rates in two periods, 1989-2002 vs 2003-2014, and including these periods in an interaction model., Results: The TOLAC rate was 74.9%, with a TOLAC failure rate of 16.2%, resulting in a vaginal birth rate of 62.8%. Low TOLAC rates were observed at high maternal age and in women from East Asia or Latin America. High TOLAC failure rates were observed at high maternal age, in women with less than 11 years of education, and in women of non-western origin. The effects of health system factors, i.e. delivery unit size and administrative region were considerable, on both TOLAC and TOLAC failure. The effects of several determinants changed significantly (P < 0.05) from 1989-2002 to 2003-2014: The association between non-TOLAC and maternal age > 39 years became weaker, the association between short education and TOLAC failure became stronger, and the association between TOLAC failure and small size of delivery unit became stronger., Conclusion: Low maternal age, high education, and western country of origin were associated with high TOLAC rates, and low TOLAC failure rates. Maternity unit characteristics (size and region) contributed with effects on the same level as individual determinants studied. Temporal changes were observed in determinant effects., Competing Interests: The authors have declared that no competing interests exist.

Introduction: Trial of labor (TOLAC) is an option in most preganancies after a cesarean section The objective of the study was to compare perinatal outcome in TOLAC and non-TOLAC deliveries in a population with high TOLAC rates., Material and Methods: This was a cohort study based on population data from the Medical Birth Registry of Norway. We included term, cephalic, single, second deliveries, 1989-2009, after a first cesarean section (n = 43 422). TOLAC, TOLAC failure, non-TOLAC deliveries, and after high-risk and low-risk pregnancies (no risk/any risk), were compared with respect to offspring mortality, 5-minute Apgar score Apgar < 7 and < 4, transfer to a neonatal intensive care unit, and neonatal respiratory distress syndrome., Results: Statistically significant differences were observed (P <0.05). In the low-risk group the offspring mortality was 2.3/1000 in TOLAC compared with 0.9/1000 in non-TOLAC. In the high-risk group, the offspring mortality was 3.7/1000 in TOLAC compared with 0.9/1000 in non-TOLAC, and the 5-minute Apgar score < 4 was 3.1/1000 in TOLAC compared with 0.9/1000 in non-TOLAC. In both risk groups, TOLAC delivery had a higher rate of 5-minute Apgar score < 7. In the low-risk group, non-TOLAC deliveries had a higher rate of neonatal respiratory distress syndrome than TOLAC deliveries., Conclusions: We observed higher risk of offspring mortality and lower 5-minute Apgar score in TOLAC than in non-TOLAC. Possible causes and preventive measures should be explored., (© 2018 Nordic Federation of Societies of Obstetrics and Gynecology.)

Objective: To assess whether women with a history of preterm birth, independent on the presence of prelabour rupture of the membranes (PROM) and growth deviation of the newborn, are more likely to develop preeclampsia with preterm or preterm birth in a subsequent pregnancy., Methods: We conducted a population-based cohort study, based on Medical Birth Registry of Norway between 1967 and 2012, including 742,980 women with singleton pregnancies who were followed up from their 1st to 2nd pregnancy. In the analyses we included 712,511 women after excluding 30,469 women with preeclampsia in the first pregnancy., Results: After preterm birth without preeclampsia in the first pregnancy, the risk of preterm preeclampsia in the second pregnancy was 4-7 fold higher than after term birth (odds ratios 3.5; 95% confidence interval (CI) 3.0-4.0 to 6.5; 95% CI 5.1-8.2). The risk of term preeclampsia in the pregnancy following a preterm birth was 2-3 times higher than after term birth (odds ratios 1.6; 95% CI 1.5-1.8 to 2.6; 95% CI 2.0-3.4). After spontaneous non-PROM preterm birth and preterm PROM, the risk of preterm preeclampsia was 3.3-3.6 fold higher than after spontaneous term birth. Corresponding risks of term preeclampsia was 1.6-1.8 fold higher. No significant time trends were found in the effect of spontaneous preterm birth in the first pregnancy on preterm or term preeclampsia in the second pregnancy., Conclusions: The results suggest that preterm birth, regardless of the presence of PROM, and preeclampsia share pathophysiologic mechanisms. These mechanisms may cause preterm birth in one pregnancy and preeclampsia in a subsequent pregnancy in the same woman. The association was particularly evident with preterm preeclampsia.

Background: Perinatal mortality according to birth weight has an inverse J-pattern. Our aim was to estimate the influence of familial factors on this pattern, applying a cohort sibling design. We focused on excess mortality among macrosomic infants (>2 SD above the mean) and hypothesized that the birth weight-mortality association could be explained by confounding shared family factors. We also estimated how the participant's deviation from mean sibling birth weight influenced the association., Methods and Findings: We included 1 925 929 singletons, born term or post-term to mothers with more than one delivery 1967-2011 registered in the Medical Birth Registry of Norway. We examined z-score birth weight and perinatal mortality in random-effects and sibling fixed-effects logistic regression models including measured confounders (e.g. maternal diabetes) as well as unmeasured shared family confounders (through fixed effects models). Birth weight-specific mortality showed an inverse J-pattern, being lowest (2.0 per 1000) at reference weight (z-score +1 to +2) and increasing for higher weights. Mortality in the highest weight category was 15-fold higher than reference. This pattern changed little in multivariable models. Deviance from mean sibling birth weight modified the mortality pattern across the birth weight spectrum: small and medium-sized infants had increased mortality when being smaller than their siblings, and large-sized infants had an increased risk when outweighing their siblings. Maternal diabetes and birth weight acted in a synergistic fashion with mortality among macrosomic infants in diabetic pregnancies in excess of what would be expected for additive effects., Conclusions: The inverse J-pattern between birth weight and mortality is not explained by measured confounders or unmeasured shared family factors. Infants are at particularly high mortality risk when their birth weight deviates substantially from their siblings. Sensitivity analysis suggests that characteristics related to maternal diabetes could be important in explaining the increased mortality among macrosomic infants.

Introduction: Hypertensive disorders of pregnancy (HDP) tend to recur from one pregnancy to the next. The aims of the study were to assess the recurrence risk according to type of HDP defined by gestational age at birth and to examine whether recurrence is associated with the following additional risk factors for HDP: maternal age, smoking, inter-delivery interval, diabetes, body mass index, and fetal growth restriction, and to assess temporal trends in these associations., Material and Methods: All women with two singleton births in the Medical Birth Registry of Norway 1967-2012 (n = 742 980) were included in this population-based cohort study. Logistic regression was used to calculate odds ratios for the risk of recurrent HDP according to type of HDP., Results: The highest odds ratio of recurrence was observed for the same type of HDP based on gestational age at delivery. After gestational hypertension and term preeclampsia, the risk for the same type to recur increased 10-fold, whereas after late and early preterm preeclampsia, the risk increased 27- and 97-fold, respectively. The recurrence of early preterm preeclampsia was less influenced by additional risk factors compared with term HDP. Recurrence of early preterm HDP was significantly lower from 1993 onwards., Conclusions: Recurrent HDP tended to be of the same type as the previous HDP. Risk of recurrence associated with additional risk factors was observed particularly after term. The odds ratio of recurrence of early preterm HDP was significantly lower from 1993 onwards., (© 2016 Nordic Federation of Societies of Obstetrics and Gynecology.)

Background: Diving is associated with both acute and long-term effects in several organ systems. Reduced semen quality after extreme diving and a reduced proportion of males in the offspring of divers have previously been reported., Aims: To study pregnancy outcomes in partners of professional male divers., Methods: The cohort of divers registered with the Norwegian Inshore Diving Registry was linked to the Medical Birth Registry of Norway (MBRN)., Results: In total, 6186 male divers had 10395 children registered in the MBRN during the study period. Of these, 52% were boys, compared to 51% in the general population. The partners of a subgroup of divers who were most likely to be occupationally exposed at the time of conception reported that early miscarriage was more frequent (27%) than in the general population (21%; relative risk 1.21, 95% confidence interval 1.05-1.39). Otherwise, there was a lower risk of adverse pregnancy outcomes such as preterm birth, stillbirth, low birthweight, small for gestational age and low Apgar score compared to the general population. Birthweight above 4000g was more frequent., Conclusions: We observed no reduced sex ratio in the offspring of occupational divers. Except for an increase in self-reported early miscarriage in the partners of exposed divers, we observed no excess risk of any of the adverse perinatal pregnancy outcomes studied., (© The Author 2016. Published by Oxford University Press on behalf of the Society of Occupational Medicine. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Aims: Preterm birth is a major cause of perinatal mortality and morbidity and is strongly associated with socio-economic factors. The objective of this study was to examine the associations of maternal education, marital status and ethnicity with preterm birth and to determine the extent to which such associations can be explained by the established risk factors of maternal age, parity and smoking., Methods: This was a register-based cohort study with data from the Medical Birth Registry of Norway 1999-2009 and Statistics Norway. The sample included all singleton spontaneous births in Norway from 1999 to 2009 (n=494,073). The main outcome measure was preterm birth (gestational age <37 weeks)., Results: Low maternal education and single motherhood were associated with preterm birth. After adjustment for the established risk factors, the excess risks were reduced, but remained statistically significant. The relative risk for low education was reduced from 1.50 to 1.36 and for single motherhood from 1.50 to 1.28. Women from Asia had a higher risk of preterm birth than Norwegian-born women (relative risk 1.29) with minor effects of adjustment. CONCLUSIONS SEVERAL SOCIO-ECONOMIC RISK FACTORS ARE ASSOCIATED WITH PRETERM BIRTH IN NORWAY IN ADDITION TO THE ESTABLISHED RISK FACTORS, PRENATAL HEALTH CARE SHOULD FOCUS ON HIGH-RISK GROUPS DEFINED BY MATERNAL EDUCATION, MARITAL STATUS AND ETHNICITY., (© 2016 the Nordic Societies of Public Health.)

Objective: Child-related stress following the birth of a child with special health care needs (SHCN) can take a toll on parental health. This study examined how the risk of sick leave due to psychiatric disorders (PD) among mothers of children with SHCN compares with that of mothers of children without SHCN during early motherhood., Methods: Responses from 58,532 mothers participating in the Norwegian Mother and Child Cohort Study were linked to national registries and monitored for physician-certified sick leave from the month of their child's first birthday until the month of their child's fourth birthday., Results: As compared with mothers of children without SHCN, mothers of children with mild and moderate/severe care needs were at substantial risk of a long-term sick leave due to PD in general and due to depression more specifically., Conclusions: Extensive childhood care needs are strongly associated with impaired mental health in maternal caregivers during early motherhood., (© The Author 2015. Published by Oxford University Press on behalf of the Society of Pediatric Psychology.)

Background: The purpose of this study was to investigate breastfeeding as a health indicator through routine data registered at public child health centres. The prevalence and course of breastfeeding were surveyed, as well as factors that affect breastfeeding., Material and Method: Breastfeeding status at six weeks and six months of age and other routine data were systematically recorded in a newly developed electronic medical records system (Health Profile 0-20 years) for infants attending public child health centres in Bergen in the period 2010-11. This information was linked to data from the Medical Birth Registry., Results: Of 6,093 infants, 73.6% were exclusively breastfed at six weeks of age and 18.9% at six months. In adjusted analyses, there was an association between breastfeeding cessation before six months and the factors smoking, low maternal age, marital status as single, unsatisfactory family situation and social network, and birth weight under 2,500 g. Attendance at a specialist breastfeeding centre and uncertain/abnormal sleep patterns in infants were associated with continued breastfeeding after six months., Interpretation: The medical records system «Health Profile 0-20 years», linked to the Medical Birth Registry, was well suited to studying factors that can affect breastfeeding. Mothers and infants with increased need for follow-up were identified.

Children born at term with low birth weight (LBW) are regarded growth restricted and are at particular risk of adverse health outcomes requiring a high degree of parental participation in the day-to-day care. This study examined whether their increased risk of special health care needs compared to other children may influence mothers' opportunities for participation in the labor market at different times after delivery. Data from 32,938 participants in the population-based Norwegian Mother and Child Cohort Study with singleton children born at term in 2004-2006 were linked to national registers in order to investigate the mothers' employment status when their children were 1-3 years in 2007 and 4-6 years in 2010. Children weighing less than two standard deviations below the gender-specific mean were defined as LBW children. Although not significantly different from mothers of children in the normal weight range, mothers of LBW children had the overall highest level of non-employment when the children were 1-3 years. At child age 4-6 years on the other hand, LBW was associated with an increased risk of non-employment (RR 1.39: 95 % CI 1.11-1.75) also after adjustment for factors associated with employment in general. In accordance with employment trends in the general population, our findings show that while mothers of normal birth weight children re-enter the labor market as their children grow older, mothers of LBW children born at term participate to a lesser extent in paid employment and remain at levels similar to those of mothers with younger children.

We aimed to explore why, in population studies, the positive association between normal-range birth weight and intelligence becomes negative at the highest birth weights. The study population comprised 217,746 Norwegian male singletons born at term between 1967 and 1976. All had data on birth weight and intelligence quotient (IQ) score at the time of military conscription; 137,574 had data on sibling birth weights; and 62,906 had data on male sibling birth weights. We estimated associations between birth weight and IQ score by ordinary least squares regression for the total study population and by fixed-effects regression for comparisons of brothers. The crude mean IQ score was 1.2 points (95% confidence interval (CI): 0.3, 2.2) lower for those with birth weights of 5,000 g or more compared with the reference group (with birth weights of 4,000-4,499 g). This difference leveled off to 0.0 (95% CI: -0.8, 0.9) in multivariable ordinary least squares regression and reversed to 2.2 points (95% CI: 0.3, 4.2) higher in fixed-effects regression. Results differed mainly because, at a given birth weight, participants who had a sibling with macrosomia had a lower mean IQ score. Nevertheless, within families with 1 or more macrosomic siblings, as in other families, men with higher birth weights tended to have higher IQ scores. Thus, a family-level confounder introduces a cross-level bias that cannot be detected in individual-level studies. We suggest ways in which future studies might elucidate the nature of this confounder., (© The Author 2014. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)