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Per-and polyfluoroalkyl substances (PFAS) are widespread pollutants that may impact youth adiposity patterns. We investigated cross-sectional associations between PFAS and body mass index (BMI) in teenagers/adolescents across nine European countries within the Human Biomonitoring for Europe (HBM4EU) initiative. We used data from 1957 teenagers (12-18 yrs) that were part of the HBM4EU aligned studies, consisting of nine HBM studies (NEBII, Norway; Riksmaten Adolescents 2016-17, Sweden; PCB cohort (follow-up), Slovakia; SLO CRP, Slovenia; CROME, Greece; BEA, Spain; ESTEBAN, France; FLEHS IV, Belgium; GerES V-sub, Germany). Twelve PFAS were measured in blood, whilst weight and height were measured by field nurse/physician or self-reported in ques-tionnaires. We assessed associations between PFAS and age-and sex-adjusted BMI z-scores using linear and logistic regression adjusted for potential confounders. Random-effects meta-analysis and mixed effects models were used to pool studies. We assessed mixture effects using molar sums of exposure biomarkers with toxicological/structural similarities and quantile g-computation. In all studies, the highest concentrations of PFAS were PFOS (medians ranging from 1.34 to 2.79 mu g/L). There was a tendency for negative associations with BMI z-scores for all PFAS (except for PFHxS and PFHpS), which was borderline significant for the molar sum of [PFOA and PFNA] and significant for single PFOA [beta-coefficient (95% CI) per interquartile range fold change =-0.06 (-0.17, 0.00) and-0.08 (-0.15,-0.01), respectively]. Mixture assessment indicated similar negative associations of the total mixture of [PFOA, PFNA, PFHxS and PFOS] with BMI z-score, but not all compounds showed associations in the same direction: whilst [PFOA, PFNA and PFOS] were negatively associated, [PFHxS] associated positively with BMI z-score. Our results indicated a tendency for associations of relatively low PFAS concentrations with lower BMI in European teenagers. More prospective research is needed to investigate this potential relationship and its implications for health later in life., European Commission 733032, Swedish Research Council European Commission 2017-00822

The prevalence of cryptorchidism has increased over the past decades, yet its origins remain poorly understood. Testis descent is dependent on androgens and likely affected by endocrine disrupting compounds (EDCs), targeting the androgen receptor (AR). We investigated the association between anti-androgenic activity, not derived from natural hormones, in maternal breast milk and impaired testis descent among boys. We performed a case-control study based on 199 breast milk samples from 94 mothers of cryptorchid boys and 105 random non-cryptorchid boys participating in the Norwegian HUMIS (Human Milk Study) cohort. For each participant, apolar, and polar fractions were extracted, and combined to reconstitute a mixture. Anti-androgenic activity was measured in all three fractions using the human cell-based in vitro anti-AR CALUX® assay and expressed in μg of flutamide equivalent, a well-known antiandrogen. Results from fraction analyses were compared among boys with cryptorchidism and controls using multiple logistic regression, controlling for appropriate confounders identified using a directed acyclic graph. Children's daily exposure to anti-androgenic EDCs through breastfeeding was estimated to 78 μg flutamide eq./kg of body weigh/day. The activity was higher in the polar fraction (1.48 ± 1.37 μg flutamide eq./g of milk) mainly representing non-persistent chemicals, in contrast to other fractions. However, the activity in the polar extracts was decreased when in mixtures with the apolar fraction, indicating synergistic interactions. No significant difference in the activity was observed according to cryptorchid status for polar, apolar or mixed breast milk fractions. The study showed anti-androgenic activity in nearly all human milk samples, and at levels higher than the advisory threshold. However, no significant association was observed between cryptorchidism and antiandrogenic activity measured in either polar, apolar, or mixture fractions derived from breast milk.

Triglyceride-bound fatty acids constitute the majority of lipids in human milk and may affect infant growth. We describe the composition of fatty acids in human milk, identify predictors, and investigate associations between fatty acids and infant growth using data from the Norwegian Human Milk Study birth cohort. In a subset of participants (n = 789, 30% of cohort), oversampled for overweight and obesity, we analyzed milk concentrations of detectable fatty acids. We modelled percent composition of fatty acids in relation to maternal body mass index, pregnancy weight gain, parity, smoking, delivery mode, gestational age, fish intake, and cod liver oil intake. We assessed the relation between fatty acids and infant growth from 0 to 6 months. Of the factors tested, excess pregnancy weight gain was positively associated with monounsaturated fatty acids and inversely associated with stearic acid. Multiparity was negatively associated with monounsaturated fatty acids and n-3 fatty acids while positively associated with stearic acid. Gestational age was inversely associated with myristic acid. Medium-chain saturated fatty acids were inversely associated with infant growth, and mono-unsaturated fatty acids, particularly oleic acid, were associated with an increased odds of rapid growth. Notably, excessive maternal weight gain was associated with cis-vaccenic acid, which was further associated with a threefold increased risk of rapid infant growth (OR = 2.9, 95% CI 1.2–6.6), suggesting that monounsaturated fatty acids in milk may play a role in the intergenerational transmission of obesity.

Background Exposure to endocrine-disrupting chemicals (EDCs) during the critical period of testicular descent may increase the risk of cryptorchidism and male fertility. Objective To investigate 27 potential EDCs measured in breast milk as a proxy for perinatal exposure and the risk of cryptorchidism in a prospective cohort. Method The Norwegian Human Milk Study (2002–2009) enrolled 2606 mother-infant pairs, of which 1326 were mother-son pairs. In a case-cohort design, we studied 641 male infants who had 27 EDCs already quantified in milk samples: 5 organochlorine pesticides, 14 polychlorinated biphenyls (PCBs), 6 brominated flame retardants, and 2 poly- and perfluoroalkyl substances. We defined cases of congenital, recurrent, persistent and ever-reported cryptorchidism based on questionnaires mothers completed when children were 1, 6, 12 and 24 months old. Variable selection via elastic net logistic regression identified the best cryptorchidism predictors while multivariable logistic regression models determined their effect estimates. Results The prevalence of reported congenital cryptorchidism was 6.1%, with half spontaneously descending within six months of birth, after which prevalence stabilized between 2.2 and 2.4%. The ever-reported prevalence of cryptorchidism at 1, 6, 12, or 24 months was 12.2%. Elastic net models identified PCB-74 (OR = 1.31, 95% CI: 1.001–1.703), PCB-114 (OR = 1.36, 95% CI: 1.05–1.77), PCB-194 (OR = 1.28, 95% CI: 1.03–1.53) and β-HCH (OR = 1.26, 95% CI: 1.03–1.53 (per interquartile range increase in concentration of EDCs) as best predictors of congenital cryptorchidism. No EDCs were selected for either recurrent or persistent cryptorchidism, and only PCB-194 was selected by elastic net for ever-reported cryptorchidism (OR = 1.23, 95% CI: 1.01–1.51), in contrast to unpenalized multivariable logistic regression, where most of the individual congeners of PCBs showed significant associations. Conclusion In the largest multi-pollutant analysis to date considering potential confounding from co-exposure to other chemicals, perinatal exposure to PCB-74, PCB-114, PCB-194 and β-HCH were associated with increased odds of congenital cryptorchidism. Many PCBs may falsely be associated with cryptorchidism when assessed individually, due to confounding by highly correlated chemicals. Experimental studies are warranted to confirm our findings.

Mercury (Hg), cadmium (Cd), and lead (Pb) are of great concern for food safety and infants are especially sensitive to exposure to the maternal body burden. We quantified these elements in breast milk from Norwegian mothers and determined their association with dietary habits, maternal amalgam fillings, and smoking. Breast milk (n = 300) from the Norwegian Human Milk Study (HUMIS) was analyzed using triple quadrupole inductively coupled plasma mass spectrometry, after an acidic decomposition using microwave technique. We used multiple linear regression to examine predictors of Hg and Cd in breast milk, and logistic regression to test predictors of Pb above the quantification limit. The median breast milk concentrations (minimum - maximum) were 0.20 μg Hg/kg (0.058-0.89), 0.057 μg Cd/kg (0.017-1.2), and0.67 μg Pb/kg (0.2-7.5). Cadmium showed no significant relation with any exposure variable investigated. Lead was associated with intake of liver and kidneys from game. For Hg concentration in breast milk, number of amalgam fillings and high fish consumption were significant predictors (p 0.001). We detected a significant association (p 0.01) between Hg in breast milk and maternal consumption of Atlantic halibut, lean fish, mussels and scallops and lifetime consumption of crab. Seafood intake alone explained 10% of variance, while together with amalgam explained 46% of variance in Hg concentration in breast milk. Our findings emphasize the importance of following consumer advice with respect to fish and seafood and points to amalgam as an important source for Hg exposure.

Background Early disruption of the microbial community may influence life-long health. Environmental toxicants can contaminate breast milk and the developing infant gut microbiome is directly exposed. We investigated whether environmental toxicants in breastmilk affect the composition and function of the infant gut microbiome at 1 month. We measured environmental toxicants in breastmilk, fecal short-chain fatty acids (SCFAs), and gut microbial composition from 16S rRNA gene amplicon sequencing using samples from 267 mother-child pairs in the Norwegian Microbiota Cohort (NoMIC). We tested 28 chemical exposures: polychlorinated biphenyls (PCBs), polybrominated flame retardants (PBDEs), per- and polyfluoroalkyl substances (PFASs), and organochlorine pesticides. We assessed chemical exposure and alpha diversity/SCFAs using elastic net regression modeling and generalized linear models, adjusting for confounders, and variation in beta diversity (UniFrac), taxa abundance (ANCOM), and predicted metagenomes (PiCRUSt) in low, medium, and high exposed groups. Results PBDE-28 and the surfactant perfluorooctanesulfonic acid (PFOS) were associated with less microbiome diversity. Some sub-OTUs of Lactobacillus, an important genus in early life, were lower in abundance in samples from infants with relative “high” (> 80th percentile) vs. “low” (

Background Maternal seafood intake during pregnancy and prenatal mercury exposure may influence children’s growth trajectories. Methods This study, based on the Norwegian Mother, Father and Child Cohort Study (MoBa), includes 51 952 mother-child pairs recruited in pregnancy during 2002–08 and a subsample (n = 2277) with maternal mercury concentrations in whole blood. Individual growth trajectories were computed by modelling based on child’s reported weight and length/height from 1 month to 8 years. We used linear mixed-effects regression analysis and also conducted discordant-sibling analysis. Results Maternal lean fish was the main contributor to total seafood intake in pregnancy and was positively but weakly associated with child body mass index (BMI) growth trajectory. Higher prenatal mercury exposure (top decile) was associated with a reduction in child’s weight growth trajectory, with the estimates ranging from -130 g [95% Confidence Intervals (CI) = -247, -12 g] at 18 months to -608 g (95% CI = -1.102, -113 g) at 8 years. Maternal fatty fish consumption was positively associated with child weight and BMI growth trajectory, but only in the higher mercury-exposed children (P-interaction = 0.045). Other seafood consumption during pregnancy was negatively associated with child weight growth compared with no intake, and this association was stronger for higher mercury-exposed children (P-interaction = 0.004). No association was observed between discordant maternal seafood intake and child growth in the sibling analysis. Conclusions Within a population with moderate seafood consumption and low mercury exposure, we found that maternal seafood consumption in pregnancy was associated with child growth trajectories, and the direction of the association varied by seafood type and level of prenatal mercury exposure. Prenatal mercury exposure was negatively associated with child growth. Our findings on maternal seafood intake are likely non-causal.

Introduction: To date, the evidence for an association between perfluoroalkyl substances (PFAS) exposure and attention deficit and hyperactivity disorder (ADHD) is inconclusive. Objective: We investigated the association between early life exposure to perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), and ADHD in a collaborative study including nine European population-based studies, encompassing 4,826 mother-child pairs. Methods: Concentrations of PFOS and PFOA were measured in maternal serum/plasma during pregnancy, or in breast milk, with different timing of sample collection in each cohort. We used a validated pharmacokinetic model of pregnancy and lactation to estimate concentrations of PFOS and PFOA in children at birth and at 3, 6, 12, and 24 months of age. We classified ADHD using recommended cutoff points for each instrument used to derive symptoms scores. We used multiple imputation for missing covariates, logistic regression to model the association between PFAS exposure and ADHD in each study, and combined all adjusted study-specific effect estimates using random-effects meta-analysis. Results: A total of 399 children were classified as having ADHD, with a prevalence ranging from 2.3% to 7.3% in the studies. Early life exposure to PFOS or PFOA was not associated with ADHD during childhood [odds ratios (ORs) ranging from 0.96 (95% CI: 0.87, 1.06) to 1.02 (95% CI: 0.93, 1.11)]. Results from stratified models suggest potential differential effects of PFAS related to child sex and maternal education. Conclusion: We did not identify an increased prevalence of ADHD in association with early life exposure to PFOS and PFOA. However, stratified analyses suggest that there may be an increased prevalence of ADHD in association with PFAS exposure in girls, in children from nulliparous women, and in children from low-educated mothers, all of which warrant further exploration. https://doi.org/10.1289/EHP5444. This research was primarily supported by a grant from the European Community’s Seventh Framework Program (FP7/2007–2013) under grant agreement Developmental Neurotoxicity Assessment of Mixtures in Children (DENAMIC) no. 282957. M.-A.V. is the recipient of a Research Scholars J1 Award from the Fonds de recherche du Québec–Santé. Norwegian Human Milk Study (HUMIS) research was funded by a grant from the Norwegian Research Council, under the NEVRINOR program grant agreement no. 226402; by PROTECTion against Endocrine Disruptors: Detection, mixtures, health effects, risk assessment and communication, and by European Union (EU) Horizon 2020 Marie Skłodowska-Curie Actions Innovative Training Networks–European Training Network no. 722634. We thank Anteneh Desalegn for his work in the HUMIS biobank. The study was approved by the Regional Ethics Committee for Medical Research in Norway (ref. S-02122) and the Norwegian Data Inspectorate (refs. 2002/1398), and participation did not occur until after informed consent was obtained. The Infancia y Medio Ambiente (INMA) study was funded by grants from the EU: NEWGENERIS FP6-2003-Food-3-A-016320, FP7-ENV-2011 cod 282957, HEALTH.2010.2.4.5-1; and by grants from Spain: Instituto de Salud Carlos III (Red INMA G03/176 and CB06/02/0041, FIS-FEDER:PI 03/1615, PI04/1509, PI04/1112, PI04/1436, PI04/1931, PI/04/2018, PI05/1079, PI05/1052, PI06/0867, PI06/1213, PI07/0314, PI/08/1151, PI09/02647, FIS-PI041436, FIS-PI081151, FISS-PI042018, FISS-PI09/02311, FISPI06/0867 FIS-PS09/00090, FIS-PI07/0252, PS09/00090, PI11/01007, PI11/02591, PI11/02038, PI13/1944, PI13/2032, PI14/00891, PI14/01687, PI16/1288, PI17/00663 and Miguel Servet-FEDER: CP11/00178, MS13/00054, and MSII16/00051), Generalitat de Catalunya-CIRIT 1999SGR 00241, La Fundació La Marató de TV3 (090430), Alicia Koplowitz Foundation 2017, Conselleria de Sanitat Generalitat Valenciana, Department of Health of the Basque Government (2005111093 and 2009111069), Provincial Government of Gipuzkoa (DFG06/004 and DFG08/001), Obra Social Cajastur, Universidad de Oviedo, Consejería de Salud de la Junta de Andalucía (grant no. 183/07), EU Commission (QLK4-1999-01422, QLK4-2002-00603, and CONTAMED FP7-ENV-212502), and Fundación Roger Torné. Global Health Institute Barcelona (ISGlobal) is a member of the CERCA Programme, Generalitat de Catalunya. A full roster of the INMA Project Investigators can be found at http://www.proyectoinma.org/presentacion-inma/listadoinvestigadores/en_listado-investigadores.html. The INUENDO study was funded by the European Commission’s Seventh and Fifth Framework Programmes (FP7-ENV-2008-1-226217 and QLK4-CT-2001-00202). The polychorinated biphenyl (PCB) cohort was funded by the U.S. National Institutes of Health (grants R01 CA096525 and R03 TW007152), the EU Seventh Framework Programme FP7/2007-2023 (grant agreement OBELIX, no. 227391), Slovak Research and Development Agency (grants APVT-21-016804, APVV-0571-12, APVV-0444-11), and by the ITMS project (no. 26240120033) based on the supporting operational research and development program from the European Regional Development Fund. This research was primarily supported by a grant from the European Community’s Seventh Framework Program (FP7/2007–2013) under grant agreement Developmental Neurotoxicity Assessment of Mixtures in Children (DENAMIC) no. 282957. M.-A.V. is the recipient of a Research Scholars J1 Award from the Fonds de recherche du Québec–Santé. Norwegian Human Milk Study (HUMIS) research was funded by a grant from the Norwegian Research Council, under the NEVRINOR program grant agreement no. 226402; by PROTECTion against Endocrine Disruptors: Detection, mixtures, health effects, risk assessment and communication, and by European Union (EU) Horizon 2020 Marie Skłodowska-Curie Actions Innovative Training Networks–European Training Network no. 722634. We thank Anteneh Desalegn for his work in the HUMIS biobank. The study was approved by the Regional Ethics Committee for Medical Research in Norway (ref. S-02122) and the Norwegian Data Inspectorate (refs. 2002/1398), and participation did not occur until after informed consent was obtained. The Infancia y Medio Ambiente (INMA) study was funded by grants from the EU: NEWGENERIS FP6-2003-Food-3-A-016320, FP7-ENV-2011 cod 282957, HEALTH.2010.2.4.5-1; and by grants from Spain: Instituto de Salud Carlos III (Red INMA G03/176 and CB06/02/0041, FIS-FEDER:PI 03/1615, PI04/1509, PI04/1112, PI04/1436, PI04/1931, PI/04/2018, PI05/1079, PI05/1052, PI06/0867, PI06/1213, PI07/0314, PI/08/1151, PI09/02647, FIS-PI041436, FIS-PI081151, FISS-PI042018, FISS-PI09/02311, FISPI06/0867 FIS-PS09/00090, FIS-PI07/0252, PS09/00090, PI11/01007, PI11/02591, PI11/02038, PI13/1944, PI13/2032, PI14/00891, PI14/01687, PI16/1288, PI17/00663 and Miguel Servet-FEDER: CP11/00178, MS13/00054, and MSII16/00051), Generalitat de Catalunya-CIRIT 1999SGR 00241, La Fundació La Marató de TV3 (090430), Alicia Koplowitz Foundation 2017, Conselleria de Sanitat Generalitat Valenciana, Department of Health of the Basque Government (2005111093 and 2009111069), Provincial Government of Gipuzkoa (DFG06/004 and DFG08/001), Obra Social Cajastur, Universidad de Oviedo, Consejería de Salud de la Junta de Andalucía (grant no. 183/07), EU Commission (QLK4-1999-01422, QLK4-2002-00603, and CONTAMED FP7-ENV-212502), and Fundación Roger Torné. Global Health Institute Barcelona (ISGlobal) is a member of the CERCA Programme, Generalitat de Catalunya. A full roster of the INMA Project Investigators can be found at http://www.proyectoinma.org/presentacion-inma/listadoinvestigadores/en_listado-investigadores.html. The INUENDO study was funded by the European Commission’s Seventh and Fifth Framework Programmes (FP7-ENV-2008-1-226217 and QLK4-CT-2001-00202). The polychorinated biphenyl (PCB) cohort was funded by the U.S. National Institutes of Health (grants R01 CA096525 and R03 TW007152), the EU Seventh Framework Programme FP7/2007-2023 (grant agreement OBELIX, no. 227391), Slovak Research and Development Agency (grants APVT-21-016804, APVV-0571-12, APVV-0444-11), and by the ITMS project (no. 26240120033) based on the supporting operational research and development program from the European Regional Development Fund.

Background: It has been suggested that prenatal exposure to n-3 long-chain fatty acids protects against asthma and other allergy-related diseases later in childhood. The extent to which fish intake in pregnancy protects against child asthma and rhinitis symptoms remains unclear. We aimed to assess whether fish and seafood consumption in pregnancy is associated with childhood wheeze, asthma and allergic rhinitis. Methods: We pooled individual data from 60 774 mother-child pairs participating in 18 European and US birth cohort studies. Information on wheeze, asthma and allergic rhinitis prevalence was collected using validated questionnaires. The time periods of interest were: infancy (0-2 years), preschool age (3-4 years), and school age (5-8 years). We used multivariable generalized models to assess associations of fish and seafood (other than fish) consumption during pregnancy with child respiratory outcomes in cohort-specific analyses, with subsequent random-effects meta-analyses. Results: The median fish consumption during pregnancy ranged from 0.44 times/week in The Netherlands to 4.46 times/week in Spain. Maternal fish intake during pregnancy was not associated with offspring wheeze symptoms in any age group nor with the risk of child asthma [adjusted meta-analysis relative risk (RR) per 1-time/week = 1.01, 95% confidence interval 0.97-1.05)] and allergic rhinitis at school age (RR = 1.01, 0.99-1.03). These results were consistently found in further analyses by type of fish and seafood consumption and in sensitivity analyses. Conclusion: We found no evidence supporting a protective association of fish and seafood consumption during pregnancy with offspring symptoms of wheeze, asthma and allergic rhinitis from infancy to mid childhood. This work was supported by the European Community’s Seventh Framework Program [EU- FP7- HEALTH-2009-single-stage-241604]. Details of funding per cohort are available at IJE online.

Background/Aims: Many environmental toxicants are passed to infants in utero and through breast milk. Exposure to toxicants during the perinatal period can alter growth patterns, impairing growth or increasing obesity risk. Previous studies have focused on only a few toxicants at a time, which may confound results. We investigated levels of 26 toxicants in breast milk and their associations with rapid infant growth, a risk factor for later obesity. Methods: We used data from the Norwegian HUMIS study, a multi-center cohort of 2,606 mothers and newborns enrolled between 2002 and 2008. Milk samples collected 1 month after delivery from a subset of 789 women oversampled by overweight were analyzed for toxicants including polychlorinated biphenyls (PCBs), heavy metals, and pesticides. Growth was defined as change in weight-for-age z-score between 0 and 6 months among the HUMIS population, and rapid growth was defined as change in z-score above 0.67. We used a Bayesian variable selection method to determine the exposures that most explained variation in the outcome. Identified toxicants were included in logistic and linear regression models to estimate associations with growth, adjusting for maternal age, smoking, education, pre-pregnancy body mass index (BMI), gestational weight gain, parity, child sex, cumulative breastfeeding, birth weight, gestational age, and preterm status. Results: Of 789 infants, 19.2% displayed rapid growth. The median maternal age was 29.6 years, and the median pre-pregnancy BMI was 24.0 kg/m2, with 45.3% of mothers overweight or obese. Rapid growers were more likely to be firstborn. Hexachlorobenzene, β-hexachlorocyclohexane (β-HCH), and PCB-74 were identified in the variable selection method. An interquartile range (IQR) increase in β-HCH exposure was associated with a lower odds of rapid growth (OR 0.63, 95% CI 0.42-0.94). Newborns exposed to high levels of β-HCH showed reduced infant growth (β = -0.03, 95% CI -0.05 to -0.01 for IQR increase in breast milk concentration). No other significant associations were found. Conclusions: Our results suggest that early life β-HCH exposure may be linked to slowed growth. Further research is warranted on the potential mechanism behind this association and the longer-term metabolic effects of perinatal β-HCH exposure.

Background Maternal obesity and excessive gestational weight gain may have persistent effects on offspring fat development. However, it remains unclear whether these effects differ by severity of obesity, and whether these effects are restricted to the extremes of maternal body mass index (BMI) and gestational weight gain. We aimed to assess the separate and combined associations of maternal BMI and gestational weight gain with the risk of overweight/obesity throughout childhood, and their population impact. Methods and findings We conducted an individual participant data meta-analysis of data from 162,129 mothers and their children from 37 pregnancy and birth cohort studies from Europe, North America, and Australia. We assessed the individual and combined associations of maternal pre-pregnancy BMI and gestational weight gain, both in clinical categories and across their full ranges, with the risks of overweight/obesity in early (2.0–5.0 years), mid (5.0–10.0 years) and late childhood (10.0–18.0 years), using multilevel binary logistic regression models with a random intercept at cohort level adjusted for maternal sociodemographic and lifestyle-related characteristics. We observed that higher maternal pre-pregnancy BMI and gestational weight gain both in clinical categories and across their full ranges were associated with higher risks of childhood overweight/obesity, with the strongest effects in late childhood (odds ratios [ORs] for overweight/obesity in early, mid, and late childhood, respectively: OR 1.66 [95% CI: 1.56, 1.78], OR 1.91 [95% CI: 1.85, 1.98], and OR 2.28 [95% CI: 2.08, 2.50] for maternal overweight; OR 2.43 [95% CI: 2.24, 2.64], OR 3.12 [95% CI: 2.98, 3.27], and OR 4.47 [95% CI: 3.99, 5.23] for maternal obesity; and OR 1.39 [95% CI: 1.30, 1.49], OR 1.55 [95% CI: 1.49, 1.60], and OR 1.72 [95% CI: 1.56, 1.91] for excessive gestational weight gain). The proportions of childhood overweight/obesity prevalence attributable to maternal overweight, maternal obesity, and excessive gestational weight gain ranged from 10.2% to 21.6%. Relative to the effect of maternal BMI, excessive gestational weight gain only slightly increased the risk of childhood overweight/obesity within each clinical BMI category (p-values for interactions of maternal BMI with gestational weight gain: p = 0.038, p < 0.001, and p = 0.637 in early, mid, and late childhood, respectively). Limitations of this study include the self-report of maternal BMI and gestational weight gain for some of the cohorts, and the potential of residual confounding. Also, as this study only included participants from Europe, North America, and Australia, results need to be interpreted with caution with respect to other populations. Conclusions In this study, higher maternal pre-pregnancy BMI and gestational weight gain were associated with an increased risk of childhood overweight/obesity, with the strongest effects at later ages. The additional effect of gestational weight gain in women who are overweight or obese before pregnancy is small. Given the large population impact, future intervention trials aiming to reduce the prevalence of childhood overweight and obesity should focus on maternal weight status before pregnancy, in addition to weight gain during pregnancy., Vincent Jaddoe and colleagues report that a high BMI before pregnancy, rather than excessive gestational weight gain, is more likely to contribute to childhood obesity., Author summary Why was this study done? Maternal pre-pregnancy obesity and excessive gestational weight gain are important risk factors of various pregnancy and birth complications. An accumulating body of evidence suggests that maternal obesity and excessive gestational weight gain also have persistent effects on offspring fat development. It is not clear whether these effects exist across the full ranges of maternal pre-pregnancy body mass index and gestational weight gain, what their combined effects are, and what the population impact of these effects is. What did the researchers do and find? We conducted an individual participant data meta-analysis using data from 162,129 mothers and their children from 37 pregnancy and birth cohorts from Europe, North America, and Australia to assess the separate and combined associations of maternal pre-pregnancy body mass index and gestational weight gain with the risk of overweight/obesity throughout childhood, and their population impact. We observed not only that maternal pre-pregnancy overweight and obesity were associated with an increased risk of childhood overweight/obesity, but that this risk increased gradually over the full range of maternal BMI. Similarly, the risk of childhood overweight/obesity increased across the full range of gestational weight gain. We estimated that 21.7% to 41.7% of childhood overweight/obesity prevalence could be attributed to maternal overweight and obesity together, whereas 11.4% to 19.2% could be attributed to excessive gestational weight gain. The additional effect of excessive gestational weight gain on the risk of childhood overweight/obesity was small among women who are already overweight or obese before pregnancy. What do these findings mean? Maternal pre-pregnancy BMI and, to a smaller extent, gestational weight gain are important modifiable risk factors of childhood overweight/obesity with considerable population impact. Future intervention trials aiming to reduce the prevalence of childhood overweight and obesity should focus on maternal weight status before pregnancy, in addition to weight status during pregnancy.

Understanding the role of the early-life gut microbiota in obesity is important because there may be opportunities for preventive strategies. We examined the relationships between infant gut microbiota at six times during the first two years of life and BMI at age 12 in a birth cohort of 165 children and their mothers. We found that the gut microbiota from early life to two years shows an increasingly strong association with childhood BMI. This study provides preliminary evidence that the gut microbiome at 2 years of age may offer useful information to help to identify youth who are at risk for obesity, which could facilitate more-targeted early prevention efforts., Childhood obesity is a growing problem worldwide. Recent research suggests that the gut microbiota may play an important and potentially causal role in the development of obesity and may be one mechanism that explains the transgenerational transmission of obesity risk. Here we examine the early-life gut microbiota at days 4, 10, 30, 120, 365, and 730 and the association with body mass index (BMI) z-scores at age 12 in a Norwegian prospective cohort (n = 165), and evaluate how these BMI-associated taxa relate to maternal overweight/obesity (Ow/Ob) and excessive gestational weight gain (GWG). We performed 16S rRNA gene sequencing on the gut microbiota samples. Taxonomic phylogeny at days 10 and 730 was significantly associated with childhood BMI, and the gut microbiota taxa at two years of age explained over 50% of the variation in childhood BMI in this cohort. The subset of the early-life taxa within the gut microbiota that best predicted later childhood BMI showed substantial overlap with the maternal taxa most strongly associated with maternal Ow/Ob and excessive GWG. Our results show an association between the infant gut microbiota and later BMI, and they offer preliminary evidence that the infant gut microbiota, particularly at 2 years of age, may have potential to help identify children at risk for obesity.

Background: Numerous ubiquitous environmental chemicals are established or suspected neurotoxicants, and infants are exposed to a mixture of these during the critical period of brain maturation. However, evidence for associations with the risk of attention-deficit/hyperactivity disorder (ADHD) is sparse. We investigated early-life chemical exposures in relation to ADHD. Methods: We used a birth cohort of 2606 Norwegian mother–child pairs enrolled 2002–2009 (HUMIS), and studied a subset of 1199 pairs oversampled for child neurodevelopmental outcomes. Concentrations of 27 persistent organic pollutants (14 polychlorinated biphenyls, 5 organochlorine pesticides, 6 brominated flame retardants, and 2 perfluoroalkyl substances) were measured in breast milk, reflecting the child's early-life exposures. We estimated postnatal exposures in the first 2 years of life using a pharmacokinetic model. Fifty-five children had a clinical diagnosis of ADHD (hyperkinetic disorder) by 2016, at a median age of 13 years. We used elastic net penalized logistic regression models to identify associations while adjusting for co-exposure confounding, and subsequently used multivariable logistic regression models to obtain effect estimates for the selected exposures. Results: Breast milk concentrations of perfluorooctane sulfonate (PFOS) and β‑hexachlorocyclohexane (β-HCH) were associated with increased odds of ADHD: odds ratio (OR) = 1.77, 95% confidence interval (CI): 1.16, 2.72 and OR = 1.75, 95% CI: 1.22, 2.53, per interquartile range increase in ln-transformed concentrations, respectively. Stronger associations were observed among girls than boys for PFOS (pinteraction = 0.025). p,p′‑Dichlorodiphenyltrichloroethane (p,p′-DDT) levels were associated with lower odds of ADHD (OR = 0.64, 95% CI: 0.42, 0.97). Hexachlorobenzene (HCB) had a non-linear association with ADHD, with increasing risk in the low-level exposure range that switched to a decreasing risk at concentrations above 8 ng/g lipid. Postnatal exposures showed similar results, whereas effect estimates for other chemicals were weaker and imprecise. Conclusions: In a multi-pollutant analysis of four classes of chemicals, early-life exposure to β-HCH and PFOS was associated with increased risk of ADHD, with suggestion of sex-specific effects for PFOS. The unexpected inverse associations between p,p′-DDT and higher HCB levels and ADHD could be due to live birth bias; alternatively, results may be due to chance findings. Keywords: Attention-deficit/hyperactivity disorder (ADHD), Contaminants, Endocrine disrupting chemicals (EDCs), Environmental chemicals, Hyperkinetic disorder, Neurodevelopment

Background/aim Presystemic biotransformation of metals by gut microbiota alters their bioaccessibility and toxicity in experimental studies. Humans are chronically exposed to arsenic through contaminated food and groundwater, and exposure occurs during critical periods of early-life development via transplacental and lactational transfer. We investigated if gut microbiota modulated arsenic speciation. Methods This study was based on the Norwegian HUMIS-NoMIC birth cohort. Total arsenic (tAs) and water-soluble arsenic species (including the organic forms dimethylarsinate and arsenobetaine) were quantified in breastmilk collected at one month postpartum. Gut microbiota was sequenced in maternal faecal samples collected 4 days postpartum using Illumina 16S rRNA amplicon analysis. We assessed associations between α-diversity (Shannon’s, phylogenetic, and OTU richness), β-diversity, and taxonomic composition of gut microbiota and the profile of arsenic species in breastmilk. Results The median (interquartile range) of tAs was 0.33 µg/kg (0.08–0.65). Both fatty and lean fish intake was strongly associated with arsenic concentrations in breastmilk. Increasing α-diversity measures were associated with decreasing tAs and also with specific arsenic species. There were no consistent associations for β-diversity. Preliminary analyses revealed associations between arsenic speciation and differential abundances of taxa. Conclusion There were indications that maternal gut microbiota modulated the chemical forms of arsenic presenting in breastmilk, although it was not possible to establish directionality of associations in this observational study. This warrants further research as gut microbiota are amenable to interventions and may modulate the toxicity of environmental metal exposures.

Background/aim Numerous ubiquitous environmental chemicals are established or suspected neurotoxicants, and infants are exposed to a mixture of these during the critical period of brain maturation. Evidence for associations with the risk of attention-deficit/hyperactivity disorder (ADHD) is sparse. We investigated measured perinatal and estimated postnatal chemical exposure levels in relation to ADHD. Methods We used a birth cohort of Norwegian mother–child pairs enrolled 2005–2009 (HUMIS-NoMIC). In a subset of 1199 oversampled for neurodevelopmental outcomes, 27 persistent organic pollutants were measured in maternal breastmilk samples (14 PCBs, 5 organochlorine pesticides, 6 brominated flame retardants, and 2 perfluoroalkyl substances). We modelled pre- and postnatal exposures using a pharmacokinetic model. ADHD (n=40) was identified based on an ICD-10 diagnosis of hyperkinetic disorder in the national patient registry by 2014 (median age of 10.3 years). To identify associations and adjust for co-exposure confounding, we used elastic net penalised logistic regression models, and then used multivariable logistic regression models to obtain effect estimates for the selected exposures. Results Perfluorooctane sulfonate (PFOS) and β -hexachlorocyclohexane ( β -HCH) were associated with increased odds and hexachlorobenzene (HCB) with decreased odds of ADHD diagnosis [confounder-adjusted odds ratio (OR) per interquartile range increase in breastmilk levels: 2.04 for PFOS; OR=1.64 for β -HCH; OR=0.36 for HCB]. Postnatal exposures showed similar results, whereas effect estimates for other chemicals were imprecise. Conclusion In a multi-pollutant analysis of four classes of chemicals, early-life exposure to several persistent organic pollutants was associated with ADHD.

Background Preterm infants have low gut microbial diversity and few anaerobes. It is unclear whether the low diversity pertains to prematurity itself or is due to differences in delivery mode, feeding mode or exposure to antibiotics. Methods The Norwegian Microbiota Study (NoMIC) was established to examine the colonization of the infant gut and health outcomes. 16S rRNA gene Illumina amplicon-sequenced samples from 519 children (160 preterms), collected at 10 days, 4 months and 1 year postnatally, were used to calculate alpha diversity. Short-chain fatty acids (SCFA) were analysed with gas chromatography and quantified using flame ionization detection. We regressed alpha diversity on gestational age, taking into account possible confounding and mediating factors, such as breastfeeding and antibiotics. Taxonomic differences were tested using Analysis of Composition of Microbiomes (ANCOM) and SCFA profile (as a functional indicator of the microbiota) was tested by Wilcoxon rank-sum. Results Preterm infants had 0.45 Shannon units lower bacterial diversity at 10 days postnatally compared with infants born at term (95% confidence interval: -0.60, -0.32). Breastfeeding status and antibiotic exposure were not significant mediators of the gestational age-diversity association, although time spent in the neonatal intensive care unit was. Vaginally born, exclusively breastfed preterm infantss not exposed to antibiotics at 10 days postnatally had fewer Firmicutes and more Proteobacteria than children born at term and an SCFA profile indicating lower saccharolytic fermentation. Conclusions Preterm infants had distinct gut microbiome composition and function in the early postnatal period, not explained by factors more common in preterms, such as shorter breastfeeding duration, more antibiotics or caesarean delivery.

International audience; Background - Attention-deficit/hyperactivity disorder (ADHD) is increasing worldwide for reasons largely unknown and environmental chemicals with neurotoxic properties, such as persistent organic pollutants (POPs), have been proposed to play a role. We investigated the association between prenatal and postnatal exposure to polychlorinated biphenyl-153 (PCB-153), p-p´-dichlorodiphenyldichloroethylene (p-p'-DDE) and hexachlorobenzene (HCB) and ADHD in childhood. Methods - We pooled seven European birth cohort studies encompassing 4437 mother-child pairs from the general population with concentrations of PCB-153, p-p´-DDE and HCB measured in cord blood, maternal blood or milk. We then calculated prenatal (birth) and postnatal (3, 6, 12 and 24 months) POP concentrations using a pharmacokinetic model. The operational definition of ADHD varied across cohorts and ranged from doctor diagnosis obtained from patient registries to maternal or teachers reports. We used multilevel (mixed) logistic regression models to estimate the associations between exposure to POPs at birth, 3, 6, 12 and 24 months and ADHD. Results - The global prevalence of ADHD in our study was 6%. The mean age at assessment of ADHD was 5.8 years (range: 3.8-9.5 years). We found no association between exposure to PCB-153, p-p´-DDE and HCB at any age point between birth and 24 months and ADHD, in the pooled analyses (pooled odds ratios ranging from 1.00 to 1.01). A number of sensitivity analyses gave basically the same results. Conclusions - In the largest study to date of 4437 children in seven European birth cohorts, we did not observe any association between either pre- or postnatal exposure (up to 24 months) to PCB-153, p-p´-DDE and HCB and the risk of ADHD before the age of 10 years.

Background: Infants are exposed to persistent environmental contaminants through breast milk, yet studies assessing the health effects of postnatal exposure are lacking. Existing postnatal exposure assessment is either too simple (lactation exposure model, LEM) or requires complex physiologically-based pharmacokinetic (PBPK) models. Objectives: We present equations for postnatal exposure calculations. We applied these equations to study the effect of hexachlorobenzene (HCB) on infant growth in the two first years of life. Methods: HCB was measured in breast milk samples in 449 mother-child pairs participating in the Norwegian birth cohort study HUMIS. We used these concentrations, mother's weight, height and age, together with child's weight at 8 age points, and proportion of milk consumed each month, to calculate HCB concentrations in the infant over age. We then estimated the association between HCB and infant growth using a linear mixed model. Results: Children exposed to HCB via mother's milk reached concentrations 1–5 times higher than the mother. HCB was associated with lower weight gain in the first 2 years (−33 g per unit HCB and month, 95% CI: −38, −27 at 6 months). Associations were stronger during the first 3 months (−57 g per unit HCB and month, 95% CI: −67, −49 at 1 month), indicating a critical window of effect. Our equations gave more precise estimates than the LEM. Conclusion: Our equations for postnatal exposure of lipophilic environmental toxicants give better results than the LEM and are easier to implement than the complex PBPK models. HCB exposure, especially during the first three months of life, has a negative effect on infant growth up to 2 years. Keywords: Postnatal exposure, HCB, Modeling, Infant growth, Linear mixed model

Background Infant exposure to persistent organic pollutants (POPs) may contribute to obesity. However, many studies so far have been small, focused on transplacental exposure, used an inappropriate measure to assess postnatal exposure through breastfeeding if any, or did not discern between prenatal and postnatal effects. Objectives We investigated prenatal and postnatal exposure to POPs and infant growth (a predictor of obesity). Methods We pooled data from seven European birth cohorts with biomarker concentrations of polychlorinated biphenyl 153 (PCB-153) (n = 2,487), and p,p´-dichlorodiphenyldichloroethylene (p,p´-DDE) (n = 1,864), estimating prenatal and postnatal POPs exposure using a validated pharmacokinetic model. Growth was change in weight-for-age z-score between birth and 24 months. Per compound, multilevel models were fitted with either POPs total exposure from conception to 24 months or prenatal or postnatal exposure. Results We found a significant increase in growth associated with p,p´-DDE, seemingly due to prenatal exposure (per interquartile increase in exposure, adjusted β = 0.12; 95% CI: 0.03, 0.22). Due to heterogeneity across cohorts, this estimate cannot be considered precise, but does indicate that an association with infant growth is present on average. In contrast, a significant decrease in growth was associated with postnatal PCB-153 exposure (β = –0.10; 95% CI: –0.19, –0.01). Conclusion To our knowledge, this is the largest study to date of POPs exposure and infant growth, and it contains state-of-the-art exposure modeling. Prenatal p,p´-DDE was associated with increased infant growth, and postnatal PCB-153 with decreased growth at European exposure levels. Citation Iszatt N, Stigum H, Verner MA, White RA, Govarts E, Palkovicova Murinova L, Schoeters G, Trnovec T, Legler J, Pelé F, Botton J, Chevrier C, Wittsiepe J, Ranft U, Vandentorren S, Kasper-Sonnenberg M, Klümper C, Weisglas-Kuperus N, Polder A, Eggesbø M, OBELIX. 2015. Prenatal and postnatal exposure to persistent organic pollutants and infant growth: a pooled analysis of seven European birth cohorts. Environ Health Perspect 123:730–736; http://dx.doi.org/10.1289/ehp.1308005

BACKGROUND: Various studies report interactions between thyroid hormones and early life chemical exposure. Our objective was to analyse associations between markers of endocrine disrupting chemical exposure and thyroid function in newborns, determined in heel prick blood spots.METHODS: Three European mother-child cohorts (FLEHSI - Belgium, HUMIS - Norway, and the PCB cohort - Slovakia. Total n=1784) were pooled for the purpose of this study. Data on Thyroid Stimulating Hormone (TSH) was obtained from national neonatal screening registries, and cord plasma and/or breast milk was collected to determine exposure to various chemicals. Multiple regression models were composed with exposure and cohort as fixed factors, and adjustments were made for a priori defined covariates.RESULTS: Median TSH concentrations were 1.00, 1.10, and 2.76 mU/l, for the Belgian, Norwegian, and the Slovak cohort, respectively. For polychlorinated biphenyl (PCB)-153 and dichlorodiphenyldichloroethylene (p,p'-DDE), children in the third exposure quartiles had a 12 - 15% lower TSH at birth. Results remained unchanged after additional adjustment for birth weight and gestational weight gain. No effect on TSH was observed for the other compounds.CONCLUSION: Early life exposure to PCB-153, and p,p'-DDE was associated with newborn TSH levels. Higher exposure levels were associated with 12-15% lower TSH levels.Pediatric Research (2017); doi:10.1038/pr.2017.50.

Author(s): Dahl, Cecilie; Stanislawski, Maggie; Iszatt, Nina; Mandal, Siddhartha; Lozupone, Catherine; Clemente, Jose C; Knight, Rob; Stigum, Hein; Eggesbo, Merete | Abstract: ObjectivePreterm birth is the main reason for neonatal deaths worldwide. We investigate whether maternal gut microbiota may play a previously overlooked role.MethodsThe Norwegian Microbiota Study (NoMIC) is a case control study on preterm birth (l259 days of gestation, calculated primarily based on the last menstrual period), including two consecutively born term infants per infant born prematurely. Eligible mothers were fluent in Norwegian and recruited from the maternity ward at a county hospital in Eastern Norway in the period 2002-2005. Fecal samples were collected at day 4 postpartum, and analyzed using 16S ribosomal RNA gene sequencing. We used samples from 121 mothers giving birth vaginally. Measures of alpha diversity (Shannon, Phylogenetic Diversity and Observed Operational Taxonomic Units) and microbiome composition were combined with information from the Medical Birth Registry, pregnancy journals, and questionnaires.ResultsThe association between maternal gut diversity and preterm delivery was examined using logistic regression. One IQR increase in Shannon diversity was significantly associated with 38% lower odds of spontaneous preterm birth, (95% confident interval (CI): 1%, 61%), and the association was stronger when adjusting for maternal age, marital status, ethnicity, parity, BMI, education, antibiotic use, pets in the household, income and smoking (48% lower odds, 95% CI: 4.2%, 72%). Mothers delivering prematurely also had lower abundance of OTUs belonging to Bifidobacterium and Streptococcus, and of the Clostridiales order.ConclusionAnalysis of maternal gut microbiota using next-generation sequencing shows that low gut diversity, with a distinct microbial composition, is associated with spontaneous preterm delivery.

During 2003–2004, United Utilities water company in North West England introduced enhanced coagulation (EC) to four treatment works to mitigate disinfection by-product (DBP) formation. This enabled examination of the relation between DBPs and birth outcomes whilst reducing socioeconomic confounding. We compared stillbirth, and low and very low birth weight rates three years before (2000–2002) with three years after (2005–2007) the intervention, and in relation to categories of THM change.We created exposure metrics for EC and trihalomethane (THM) concentration change (n = 258 water zones). We linked 429,599 live births and 2279 stillbirths from national birth registers to the water zone at birth. We used Poisson regression to model the differences in birth outcome rates with an interaction between before/after the intervention and EC or THM change.EC treatment reduced chloroform concentrations more than non-treatment (mean -29.7 µg/l vs. -14.5 µg/l), but not brominated THM concentrations. Only 6% of EC water zones received 100% EC water, creating exposure misclassification concerns. EC intervention was not associated with a statistically significant reduction in birth outcome rates. Areas with the highest chloroform decrease (30 – 65 μg/l) had the greatest percentage decrease in low -9 % (-12, -5) and very low birth weight -16% (-24, -8) rates. The interaction between before/after intervention and chloroform change was statistically significant only for very low birth weight, p = 0.02. There were no significant decreases in stillbirth rates.In a novel approach for studying DBPs and adverse reproductive outcomes, the EC intervention to reduce DBPs did not affect birth outcome rates. However, a measured large decrease in chloroform concentrations was associated with statistically significant reductions in very low birth weight rates. Keywords: Chloroform, Disinfection by-products, Trihalomethanes, Drinking-water, Low birth weight, Stillbirth

Introduction: Spontaneous preterm delivery has been linked to vaginal infections and illnesses such as inflammatory bowel disease, but few have considered whether maternal gut microbiota may play a...

Background Dioxins and dioxin-like compounds are endocrine disrupting chemicals (EDCs). Experimental studies suggest perinatal exposure to EDCs results in later obesity. However, the few epidemiological investigations on dioxins are inconclusive. We investigated perinatal exposure to dioxins and dioxin-like compounds, infant growth and body mass index (BMI) in childhood. Methods We pooled data from 3 European birth cohorts (Belgian, Norwegian, Slovak) with exposure assessment in cord blood or breast milk. Two cohorts had dioxin-like toxicity assessed using dioxin-responsive chemical-activated luciferase expression (DR-CALUX) bioassay and one cohort had measured concentrations of dioxins, furans and dioxin-like polychlorinated biphenols with CALUX relative potency values applied. Growth was cohort- and sex-specific change in weight-for-age z-score between birth and 24 months (N = 367). BMI was calculated at around 7 years (median 7.17, interquartile range [IQR] 7.00–7.37 years, N = 251), and overweight defined according to international standards for children equivalent to adult BMI > 25 kg/m2 (Cole and Lobstein, 2012). We fitted multivariate models using generalized estimating equations, and tested effect modification by sex, breastfeeding and cohort. Results per 10 pg CALUX TEQ/g lipid increase in exposure. Results Dioxin exposure was highest in the Belgian and lowest in the Norwegian cohort; median (IQR) of the pooled sample 13 (12.0) pg CALUX TEQ/g lipid. Perinatal exposure to dioxins and dioxin-like compounds appeared associated with increased growth between 0 and 24 months (adjusted estimate for change in z-score: β = 0.07, 95% CI: − 0.01, 0.14). At 7 years, dioxins exposure was associated with a statistically significant increase in BMI in girls (adjusted estimate for BMI units β = 0.49, 95% CI: 0.07, 0.91) but not in boys (β = − 0.03, 95% CI: − 0.55, 0.49) (p-interaction = 0.044). Furthermore, girls had a 54% (− 6%, 151%) increased risk of overweight at 7 years (p-interaction = 0.023). Conclusion Perinatal exposure to dioxin and dioxin-like compounds was associated with increased early infant growth, and increased BMI in school age girls. Studies in larger sample sizes are required to confirm these sex-specific effects. © 2016 Elsevier Ltd Background Dioxins and dioxin-like compounds are endocrine disrupting chemicals (EDCs). Experimental studies suggest perinatal exposure to EDCs results in later obesity. However, the few epidemiological investigations on dioxins are inconclusive. We investigated perinatal exposure to dioxins and dioxin-like compounds, infant growth and body mass index (BMI) in childhood. Methods We pooled data from 3 European birth cohorts (Belgian, Norwegian, Slovak) with exposure assessment in cord blood or breast milk. Two cohorts had dioxin-like toxicity assessed using dioxin-responsive chemical-activated luciferase expression (DR-CALUX) bioassay and one cohort had measured concentrations of dioxins, furans and dioxin-like polychlorinated biphenols with CALUX relative potency values applied. Growth was cohort- and sex-specific change in weight-for-age z-score between birth and 24 months (N = 367). BMI was calculated at around 7 years (median 7.17, interquartile range [IQR] 7.00–7.37 years, N = 251), and overweight defined according to international standards for children equivalent to adult BMI > 25 kg/m 2 (Cole and Lobstein, 2012). We fitted multivariate models using generalized estimating equations, and tested effect modification by sex, breastfeeding and cohort. Results per 10 pg CALUX TEQ/g lipid increase in exposure. Results Dioxin exposure was highest in the Belgian and lowest in the Norwegian cohort; median (IQR) of the pooled sample 13 (12.0) pg CALUX TEQ/g lipid. Perinatal exposure to dioxins and dioxin-like compounds appeared associated with increased growth between 0 and 24 months (adjusted estimate for change in z-score: β = 0.07, 95% CI: − 0.01, 0.14). At 7 years, dioxins exposure was associated with a statistically significant increase in BMI in girls (adjusted estimate for BMI units β = 0.49, 95% CI: 0.07, 0.91) but not in boys (β = − 0.03, 95% CI: − 0.55, 0.49) (p-interaction = 0.044). Furthermore, girls had a 54% (− 6%, 151%) increased risk of overweight at 7 years (p-interaction = 0.023). Conclusion Perinatal exposure to dioxin and dioxin-like compounds was associated with increased early infant growth, and increased BMI in school age girls. Studies in larger sample sizes are required to confirm these sex-specific effects.

OBJECTIVES: The aim of this study was to review epidemiologic evidence, provide summary risk estimates of the association between exposure to chlorination disinfection by-products (DBPs) and congenital anomalies, and provide recommendations for future studies. DATA SOURCES AND EXTRACTION: We included all published epidemiologic studies that evaluated a relationship between an index of DBP exposure (treatment, water source, DBP measurements, and both DBP measurements and personal characteristics) and risk of congenital anomalies. When three or more studies examined the same exposure index and congenital anomaly, we conducted a meta-analysis to obtain a summary risk estimate comparing the highest exposure group with the lowest exposure group. When five or more studies examined total trihalomethane (TTHM) exposure and a specific congenital anomaly, we conducted a meta-analysis to obtain exposure-response risk estimates per 10 microg/L TTHM. DATA SYNTHESIS: For all congenital anomalies combined, the meta-analysis gave a statistically significant excess risk for high versus low exposure to water chlorination or TTHM [17%; 95% confidence interval (CI), 3-34] based on a small number of studies. The meta-analysis also suggested a statistically significant excess risk for ventricular septal defects (58%; 95% CI, 21-107), but this was based on only three studies, and there was little evidence of an exposure-response relationship. We observed no statistically significant relationships in the other meta-analyses. We found little evidence for publication bias, except for urinary tract defects and cleft lip and palate. CONCLUSION: Although some individual studies have suggested an association between chlorination disinfection by-products and congenital anomalies, meta-analyses of all currently available studies demonstrate little evidence of such an association. This work was conducted without specific allocated funding, but contributions were made by researchers working on the Integrated Assessment of Health Risks of Environmental Stressors in Europe (INTARESE) project, cofunded by the European Commission under the Sixth Framework Programme (2002–2006), and the Health Impacts of Long-term Exposure to Disinfection By-products in Drinking Water in Europe (HIWATE) project, which is a 3.5-year Specific Targeted Research Project funded under the European Union Sixth Framework Programme for Research and Technological Development by the Research Directorate–Biotechnology, Agriculture and Food Research Unit (contract Food-CT-2006-036224)

Low-level exposure to polychlorinated biphenyl-153 (PCB-153) and dichlorodiphenyldichloroethylene (p-p′-DDE) can impair fetal growth; however, the exposure–response relationship and effect modifiers of such association are not well established. This study is an extension of an earlier European meta-analysis. Our aim was to explore exposure–response relationship between PCB-153 and p-p′-DDE and birth outcomes; to evaluate whether any no exposure–effect level and susceptible subgroups exist; and to assess the role of maternal gestational weight gain (GWG). We used a pooled dataset of 9377 mother–child pairs enrolled in 14 study populations from 11 European birth cohorts. General additive models were used to evaluate the shape of the relationships between organochlorine compounds and birth outcomes. We observed an inverse linear exposure–response relationship between prenatal exposure to PCB-153 and birth weight [decline of 194 g (95% CI −314, −74) per 1 μg/L increase in PCB-153]. We showed effects on birth weight over the entire exposure range, including at low levels. This reduction seems to be stronger among children of mothers who were non-Caucasian or had smoked during pregnancy. The most susceptible subgroup was girls whose mothers smoked during pregnancy. After adjusting for absolute GWG or estimated fat mass, a reduction in birth weight was still observed. This study suggests that the association between low-level exposure to PCB-153 and birth weight exists and follows an inverse linear exposure–response relationship with effects even at low levels, and that maternal smoking and ethnicity modify this association. Keywords: Biomarkers of exposure, Persistent organic pollutants, Polychlorinated biphenyls (PCBs), Dichlorodiphenyldichloroethylene (DDE), Birth weight

Perfluoroalkyl substances (PFASs) are chemicals with potential neurotoxic effects although the current evidence is still limited. This study investigated the association between perinatal exposure to perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) and neuropsychological development assessed at 6, 12 and 24 months. We measured PFOS and PFOA in breast milk samples collected one month after delivery by mothers of children participating in the HUMIS study (Norway). Cognitive and psychomotor development was measured at 6 and at 24 months using the Ages and Stages Questionnaire (ASQ-II). Behavioral development was assessed using the infant–toddler symptom checklist (ITSC) at 12 and at 24 months. Weighted logistic regression and weighted negative binomial regression models were applied to analyze the associations between PFASs and ASQ-II and ITSC, respectively. The median concentration of PFOS was 110 ng/L, while the median for PFOA was 40 ng/L. We did not detect an increased risk of having an abnormal score in ASQ-II at 6 months or 24 months. Moreover, no consistent increase in behavioral problems assessed at 12 and 24 months by ITSC questionnaire was detected. We observed no association between perinatal PFOS and PFOA exposure and early neuropsychological development. Further longitudinal studies are needed to confirm the effects of these compounds on neuropsychological development in older children. Keywords: Nervous system, Child development, Neuropsychology, Perfluorooctanoic acid, Perfluorooctane sulfonic acid, Epidemiology

Objectives Disinfection by-products (DBPs) have been associated with adverse semen outcomes in laboratory animals, although the evidence for trihalomethanes (THMs) is limited. Three small epidemiological studies found little evidence for an association between DBPs and adverse semen outcomes in humans. Using data from a large case–referent study (Chemicals and Pregnancy Study, Chaps-UK), we investigated the association between total THM (TTHM), chloroform and total brominated THMs and sperm concentration, percent motile sperm and motile sperm concentration (MSC). Methods Chaps-UK recruited men from 13 fertility clinics in nine urban centres across England and Wales between 1999 and 2002. We linked modelled THM concentrations in water zones to semen quality data for 642 cases (men with low MSC) and 926 referents (other men investigated for infertility), based on the men9s residence during semen sampling. We assessed risk of low MSC in relation to DBP exposure using continuous THM concentrations. A secondary analysis investigated continuous outcomes (MSC, sperm concentration and percent motile sperm). Results In the case–referent analysis there was little evidence of elevated risk associated with chloroform, total brominated THM or TTHM concentration after adjustment (OR per 10 µg/L TTHM 1.01; 95% CI 0.91 to 1.12). Similarly, there was no significant effect of THMs on the continuous outcomes. Conclusions In the largest study to date on DBPs in public water supplies, and semen quality we found that concentrations of THMs were not associated with poor semen quality. Large-scale investigation of other DBPs (eg, haloacetic acids) and other semen quality parameters (eg, sperm morphology and/or sperm DNA integrity) is recommended.

It is acknowledged that some obesity trajectories are set early in life, and that rapid weight gain in infancy is a risk factor for later development of obesity. Identifying modifiable factors associated with early rapid weight gain is a prerequisite for curtailing the growing worldwide obesity epidemic. Recently, much attention has been given to findings indicating that gut microbiota may play a role in obesity development. We aim at identifying how the development of early gut microbiota is associated with expected infant growth. We developed a novel procedure that allows for the identification of longitudinal gut microbiota patterns (corresponding to the gut ecosystem developing), which are associated with an outcome of interest, while appropriately controlling for the false discovery rate. Our method identified developmental pathways of Staphylococcus species and Escherichia coli that were associated with expected growth, and traditional methods indicated that the detection of Bacteroides species at day 30 was associated with growth. Our method should have wide future applicability for studying gut microbiota, and is particularly important for translational considerations, as it is critical to understand the timing of microbiome transitions prior to attempting to manipulate gut microbiota in early life., Author Summary Some obesity trajectories are set early in life, with rapid weight gain being a risk factor for later development of obesity. Recently, much attention has been given to findings indicating that gut microbiota may play a role in obesity development. The existence of time-dependent exposure windows, which rely on stimuli from the gut to initiate healthy development, gives the evolution of early life gut microbiota a critical role in human health. We identified children that followed their expected growth trajectories at six months of life, and those that had deviated. We then developed a novel statistical approach that allowed the identification of longitudinal gut microbiota patterns (e.g. a particular species was detected at days 4, 10, and 30 and not detected at day 120) that were associated with expected growth, while appropriately restricting the false discovery rate. We further identified when a deviation from the proposed longitudinal gut microbiota patterns would result in an abnormal growth outcome (either rapid or decreased growth at six months of life). We found developmental pathways of Staphylococcus species and Escherichia coli that were associated with expected growth, as well as indications that Bacteroides species at day 30 was associated with growth.

Nina Iszatt, MRC-HPA Centre for Environment and Health, Department of Epidemiology and Biostatistics, Imperial College London, London, UK Mark J. Nieuwenhuijsen, Center for Research in Environmental Epidemiology (CREAL), Barcelona, Spain James Bennett, MRC-HPA Centre for Environment and Health, Department of Epidemiology and Biostatistics, Imperial College London, London, UK Mireille B. Toledano, MRC-HPA Centre for Environment and Health, Department of Epidemiology and Biostatistics, Imperial College London, London, UK

Background The relationship between the use of biocides and insect repellents and the risk of hypospadias was examined in a large case–control study in the South East of England. Methods A case–control study was carried out among 471 cases of hypospadias referred to surgeons, and 490 randomly selected population-based controls, born between 1 January 1997 and 30 September 1998. Telephone interviews were conducted between September 2000 and March 2003. The questionnaire included information on demographic, lifestyle and environmental factors, including the use of biocides and insect repellents, during pregnancy. A total biocide score was created from summing positive responses to an eight-item biocide exposure questionnaire. Results The use of insect repellent (adjusted OR 1.81, 95% CI 1.06 to 3.11) during the first trimester of pregnancy was associated with risk of hypospadias, but none of the biocides, or indicators for them, except for the total biocide score for the highest two exposure categories (score 3: adjusted OR 1.73, 95% CI 1.02 to 2.94; and scores 4 and 5 combined: adjusted OR 2.98, 95% CI 1.01 to 8.78) showed statistically significant associations. Conclusion The authors found an association between the use of insect repellent and total biocide score and risk of hypospadias. In particular, the use of insect repellent warrants further investigation, specifically in relation to type, content and frequency of use since this information was missing in the current study.

This paper summarizes the epidemiological evidence for adverse health effects associated with disinfection by-products (DBPs) in drinking water and describes the potential mechanism of action. There appears to be good epidemiological evidence for a relationship between exposure to DBPs, as measured by trihalomethanes (THMs), in drinking water and bladder cancer, but the evidence for other cancers including colorectal cancer is inconclusive and inconsistent. There appears to be some evidence for an association between exposure to DBPs, specifically THMs, and little for gestational age/intrauterine growth retardation and, to a lesser extent, pre-term delivery, but evidence for relationships with other outcomes such as low birth weight, stillbirth, congenital anomalies and semen quality is inconclusive and inconsistent. Major limitations in exposure assessment, small sample sizes and potential biases may account for the inconclusive and inconsistent results in epidemiological studies. Moreover, most studies have focused on total THMs as the exposure metric, whereas other DBPs appear to be more toxic than the THMs, albeit generally occurring at lower levels in the water. The mechanisms through which DBPs may cause adverse health effects including cancer and adverse reproductive effects have not been well investigated. Several mechanisms have been suggested, including genotoxicity, oxidative stress, disruption of folate metabolism, disruption of the synthesis and/or secretion of placental syncytiotrophoblast-derived chorionic gonadotropin and lowering of testosterone levels, but further work is required in this area.