Maternal intrahepatic cholestasis of pregnancy and neurodevelopmental conditions in offspring: A population-based cohort study of 2 million Swedish children.

BACKGROUND: Intrahepatic cholestasis of pregnancy (ICP) is the most common obstetric liver disorder and is associated with an increased risk of iatrogenic preterm birth and adverse infant outcomes. Hence, there are several plausible pathways through which ICP could affect offspring neurodevelopment. However, to the best of our knowledge, no studies have investigated these associations. Thus, we aimed to determine whether ICP is associated with offspring neurodevelopmental conditions. METHODS AND FINDINGS: In this Swedish register-based cohort study, we included singleton non-adopted children born in Sweden between the 1st of January 1987 and the 31st of December 2010, who were resident in Sweden >5 years, with no missing covariate information, which we followed until the 31st of December 2016. Maternal ICP diagnosis and the date of the initial diagnosis during pregnancy were obtained from the National Patient Register. Offspring diagnoses of attention deficit/hyperactivity disorder (ADHD), autism, or intellectual disability were obtained from the National Patient Register, and the dispensation of ADHD medications were obtained from the Prescribed Drug Register. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using logistic regression while controlling for observed confounders and unobserved confounders shared among full siblings and maternal full cousins. A total of 2,375,856 children were included in the study; 81.6% of them were of Nordic origin, and 51.4% were male. Of these, 10,378 (0.44%) were exposed to ICP. During a median of 18 years follow-up (interquartile range 11 to 24), 143,746 (6.05%) of children were diagnosed with a neurodevelopmental condition. After adjusting for child's sex, birth year, birth month, maternal age, highest parental education level, maternal birth country, birth order, maternal psychiatric history, ICP was associated with increased odds of offspring neurodevelopmental conditions (OR 1.22, 95% CI 1.13 to 1.31), particularly among those exposed to early-onset ICP (OR 2.38, 95% CI 1.71 to 3.30) as compared to ICP diagnosed after reaching term (≥37 weeks of gestation) (OR 1.08, 95% CI 0.97 to 1.20). The findings of early-onset ICP were consistent in family-based analyses. Within-family comparisons of full maternal cousins yielded an OR of 2.99 (95% CI 1.48 to 6.04), and comparisons of full siblings showed an OR of 1.92 (95% CI 0.92 to 4.02), though the latter was less precise. The findings were consistent across specific neurodevelopmental conditions and different analytical approaches. The primary limitations of this study included its observational design, the absence of data on ICP therapeutics, and the lack of bile acid measures. CONCLUSIONS: In this study, we observed that exposure to ICP during gestation is associated with an increased likelihood of neurodevelopmental conditions in offspring, particularly in cases of early-onset ICP. Further studies are warranted to better understand the role of early-ICP in offspring neurodevelopment.

Acetaminophen Use During Pregnancy and Children's Risk of Autism, ADHD, and Intellectual Disability.

Importance: Several studies suggest that acetaminophen (paracetamol) use during pregnancy may increase risk of neurodevelopmental disorders in children. If true, this would have substantial implications for management of pain and fever during pregnancy. Objective: To examine the associations of acetaminophen use during pregnancy with children's risk of autism, attention-deficit/hyperactivity disorder (ADHD), and intellectual disability. Design, Setting, and Participants: This nationwide cohort study with sibling control analysis included a population-based sample of 2 480 797 children born in 1995 to 2019 in Sweden, with follow-up through December 31, 2021. Exposure: Use of acetaminophen during pregnancy prospectively recorded from antenatal and prescription records. Main Outcomes and Measures: Autism, ADHD, and intellectual disability based on International Classification of Diseases, Ninth Revision and International Classification of Diseases, Tenth Revision codes in health registers. Results: In total, 185 909 children (7.49%) were exposed to acetaminophen during pregnancy. Crude absolute risks at 10 years of age for those not exposed vs those exposed to acetaminophen were 1.33% vs 1.53% for autism, 2.46% vs 2.87% for ADHD, and 0.70% vs 0.82% for intellectual disability. In models without sibling control, ever-use vs no use of acetaminophen during pregnancy was associated with marginally increased risk of autism (hazard ratio [HR], 1.05 [95% CI, 1.02-1.08]; risk difference [RD] at 10 years of age, 0.09% [95% CI, -0.01% to 0.20%]), ADHD (HR, 1.07 [95% CI, 1.05-1.10]; RD, 0.21% [95% CI, 0.08%-0.34%]), and intellectual disability (HR, 1.05 [95% CI, 1.00-1.10]; RD, 0.04% [95% CI, -0.04% to 0.12%]). To address unobserved confounding, matched full sibling pairs were also analyzed. Sibling control analyses found no evidence that acetaminophen use during pregnancy was associated with autism (HR, 0.98 [95% CI, 0.93-1.04]; RD, 0.02% [95% CI, -0.14% to 0.18%]), ADHD (HR, 0.98 [95% CI, 0.94-1.02]; RD, -0.02% [95% CI, -0.21% to 0.15%]), or intellectual disability (HR, 1.01 [95% CI, 0.92-1.10]; RD, 0% [95% CI, -0.10% to 0.13%]). Similarly, there was no evidence of a dose-response pattern in sibling control analyses. For example, for autism, compared with no use of acetaminophen, persons with low (<25th percentile), medium (25th-75th percentile), and high (>75th percentile) mean daily acetaminophen use had HRs of 0.85, 0.96, and 0.88, respectively. Conclusions and Relevance: Acetaminophen use during pregnancy was not associated with children's risk of autism, ADHD, or intellectual disability in sibling control analysis. This suggests that associations observed in other models may have been attributable to familial confounding.

Associations between maternal metabolic conditions and neurodevelopmental conditions in offspring: the mediating effects of obstetric and neonatal complications.

BACKGROUND: Maternal pre-gestational diabetes (PGDM), gestational diabetes mellitus (GDM), and overweight/obesity have been associated with increased risks of offspring neurodevelopmental conditions (NDCs) including autism, intellectual disability (ID), and attention deficit/hyperactivity disorder (ADHD). Less is known about whether and how obstetric and neonatal complications (e.g., preterm birth, neonatal asphyxia) could mediate these associations. METHODS: In this Swedish register-based cohort study, we examined complications during pregnancy, delivery, and the neonatal period as potential mediators of the relationships between maternal metabolic conditions and offspring NDCs. We quantified the extent to which these obstetric and neonatal factors could mediate the associations of maternal metabolic conditions with offspring NDCs by applying parametric regression models for single mediation analyses and weighting-based methods for multiple mediation analyses under counterfactual frameworks. RESULTS: The study sample included 2,352,969 singleton children born to 1,299,692 mothers from 1987-2010 who were followed up until December 31, 2016, of whom 135,832 children (5.8%) were diagnosed with at least one NDC. A substantial portion of the association between maternal PGDM and children's odds of NDCs could be explained by the combined group of obstetric and neonatal complications in the multiple mediation analysis. For instance, these complications explained 44.4% of the relationship between maternal PGDM and offspring ID risk. The proportion of the relationship between maternal overweight/obesity and children's risk of NDCs that could be explained by obstetric and neonatal complications was considerably smaller, ranging from 1.5 to 8.1%. Some complications considered on their own, including pregnancy hypertensive diseases, preterm birth, neonatal asphyxia, and hematological comorbidities, could explain at least 10% of the associations between maternal PGDM and offspring NDCs. Complications during the neonatal period showed a stronger joint mediating effect for the relationship between PGDM and offspring NDCs than those during pregnancy or delivery. CONCLUSIONS: Obstetric and neonatal complications could explain nearly half of the association between maternal PGDM and offspring risk of NDCs. The mediating effects were more pronounced for complications during the neonatal period and for specific complications such as pregnancy hypertensive diseases, preterm birth, neonatal asphyxia, and hematological comorbidities. Effective preventive strategies for offspring NDCs should holistically address both the primary metabolic issues related to PGDM and the wide array of potential complications, especially those in the neonatal period.

Random capillary glucose levels throughout pregnancy, obstetric and neonatal outcomes, and long-term neurodevelopmental conditions in children: a group-based trajectory analysis.

BACKGROUND: Gestational diabetes mellitus (GDM) is associated with both short- and long-term risks, although it is unknown if risks vary by severity, timing, and duration of gestational hyperglycemia. We aimed to identify trajectories of random capillary glucose (RCG) levels throughout pregnancy and assess their associations with both obstetric/neonatal outcomes and children's risk of neurodevelopmental conditions (NDCs) (i.e., autism, intellectual disability, and attention-deficit/hyperactivity disorders [ADHD]). METHODS: A population-based cohort study was conducted involving 76,228 children born to 68,768 mothers without pregestational diabetes. Group-based trajectory modeling was utilized to identify distinct glucose trajectories across RCG values throughout the course of pregnancy. The associations between these trajectory groups and obstetric/neonatal outcomes as well as children's NDCs were then assessed using generalized estimating equation models with a logit link. The Benjamini-Hochberg (BH) procedure was employed to adjust P-values for multiple comparisons, controlling the false discovery rate (FDR). RESULTS: Five distinct glucose trajectory groups were identified, each with varying percentages diagnosed with GDM. Their associations with obstetric/neonatal outcomes as well as children's NDCs varied. For example, when compared to the "Persistently Low" group, other groups exhibited varying degrees of increased risk for large-for-gestational-age babies, with the exception of the "High in Early Pregnancy" group. Compared to the "Persistently Low" group, all other trajectory groups were associated with NDC outcomes, except the "High in Mid-Pregnancy" group. However, none of the associations with offspring NDCs remained significant after accounting for the FDR correction. CONCLUSIONS: Persistent high glucose levels or moderately elevated glucose levels throughout pregnancy, as well as transient states of hyperglycemia in early or mid-pregnancy, were found to be associated with increased risks of specific obstetric and neonatal complications, and potentially offspring NDCs. These risks varied depending on the severity, timing, duration, and management of hyperglycemia. The findings underscore the need for continuous surveillance and individualized management strategies for women displaying different glucose trajectories during pregnancy. Limitations such as potential residual confounding, the role of mediators, and small sample size should be addressed in future studies.

Rates of maternal weight gain over the course of pregnancy and offspring risk of neurodevelopmental disorders.

BACKGROUND: Previous studies have suggested that gestational weight gain (GWG) outside an optimal range increases the risks of neurodevelopmental disorders (NDDs) in offspring including autism spectrum disorder (ASD), intellectual disability (ID), and attention deficit/hyperactivity disorder (ADHD). The sequential development of the fetal brain suggests that its vulnerability may vary depending on the timing of exposure. Therefore, we aimed to investigate the associations of not only gestational age-standardized total GWG (GWG z-scores) but also the rate of GWG (RGWG) in the second and third trimesters with risks of NDDs in offspring. METHODS: In this population-based cohort study, we used maternal weight data from antenatal care records collected for 57,822 children born to 53,516 mothers between 2007 and 2010 in the Stockholm Youth Cohort. Children were followed from 2 years of age to December 31, 2016. GWG z-scores and RGWG (kg/week) in the second and third trimesters were considered as continuous variables in cox regression models, clustered on maternal identification numbers. Nonlinear relationships were accommodated using restricted cubic splines with 3 knots. RGWG were also categorized according to the 2009 US Institute of Medicine (IOM) guidelines for optimal GWG. According to the IOM guidelines, the optimal rate of GWG for the second and third trimesters for underweight, normal weight, overweight, and obese categories were 0.44-0.58, 0.35-0.50, 0.23-0.33, and 0.17-0.27 kg/week, respectively. RESULTS: During a mean follow-up of 5.4 years (until children were on average 7.4 years old), 2205 (3.8%) children were diagnosed with NDDs, of which 1119 (1.9%) received a diagnosis of ASD, 1353 (2.3%) ADHD, and 270 (0.5%) ID. We observed a J-shaped association between total GWG z-score and offspring risk of NDDs, with higher total GWG (GWG z-score = 2) associated with 19% increased risk of any NDD (95% CI = 3-37%) and lower total GWG (GWG z-score = - 2) associated with 12% increased risk of any NDDs (95% CI = 2-23%), compared to the reference (GWG z-score = 0). In the second trimester, lower RGWG (0.25 kg/week) was associated with a 9% increased risk of any NDD diagnosis (95% CI = 4-15%) compared to the median of 0.57 kg/week, with no apparent relationship between higher RGWG and risk of NDDs. In the third trimester, there was no apparent association between lower RGWG and risk of NDDs, though higher RGWG (1 kg/week) was associated with a 28% increased risk of NDD diagnosis (95% CI = 16-40%), compared to the median (0.51 kg/week). When considering categorized RGWG, we found that slow weight gain in the second trimester followed by rapid weight gain in the third trimester most significantly increased the risk of ADHD (HRadjusted = 1.55, 1.13-2.13) and ID (HRadjusted = 2.53, 1.15-5.55) in offspring. The main limitations of our study are the relatively few years for which detailed GWG data were available and the relatively short follow-up for the outcomes, limiting power to detect associations and misclassifying children who receive an NDD diagnosis later in childhood. CONCLUSIONS: The relationship between maternal weight gain and children's risk of NDDs varied according to timing in pregnancy, with the greatest risks associated with slow weight gain in the second trimester and rapid weight gain in the third trimester.

Developmental vitamin D and autism spectrum disorders: findings from the Stockholm Youth Cohort.

Animal studies indicate that early life vitamin D is crucial for proper neurodevelopment. Few studies have examined whether maternal and neonatal vitamin D concentrations influence risk of autism spectrum disorders (ASD). Participants were sampled from the Stockholm Youth Cohort, a register-based cohort in Sweden. Concentrations of total 25-hydroxyvitamin D (25OHD) were assessed from maternal and neonatal biosamples using a highly sensitive liquid chromatography tandem mass spectrometry method. The maternal sample consisted of 449 ASD cases and 574 controls, the neonatal sample: 1399 ASD cases and 1607 controls; and the paired maternal-neonatal sample: 340 ASD cases and 426 controls. Maternal 25OHD was not associated with child ASD in the overall sample. However, in Nordic-born mothers, maternal 25OHD insufficiency (25 - <50 nmol/L) at ~11 weeks gestation was associated with 1.58 times higher odds of ASD (95% CI: 1.00, 2.49) as compared with 25OHD sufficiency (≥50 nmol/L). Neonatal 25OHD < 25 nmol/L was associated with 1.33 times higher odds of ASD (95% CI: 1.02, 1.75) as compared with 25OHD ≥ 50 nmol/L. Sibling-matched control analyses indicated these associations were not likely due to familial confounding. Children with both maternal 25OHD and neonatal 25OHD below the median had 1.75 (95% CI: 1.08, 2.86) times the odds of ASD compared with children with maternal and neonatal 25OHD both below the median. Our results are consistent with an increasing body of evidence suggesting that vitamin D concentrations in early life may be associated with increased risk of neurodevelopmental disorders including ASD.

Maternal hospitalization with infection during pregnancy and risk of autism spectrum disorders.

Animal models indicate that maternal infection during pregnancy can result in behavioral abnormalities and neuropathologies in offspring. We examined the association between maternal inpatient diagnosis with infection during pregnancy and risk of ASD in a Swedish nationwide register-based birth cohort born 1984-2007 with follow-up through 2011. In total, the sample consisted of 2,371,403 persons with 24,414 ASD cases. Infection during pregnancy was defined from ICD codes. In the sample, 903 mothers of ASD cases (3.7%) had an inpatient diagnosis of infection during pregnancy. Logistic regression models adjusted for a number of covariates yielded odds ratios indicating approximately a 30% increase in ASD risk associated with any inpatient diagnosis of infection. Timing of infection did not appear to influence risk in the total Swedish population, since elevated risk of ASD was associated with infection in all trimesters. In a subsample analysis, infections were associated with greater risk of ASD with intellectual disability than for ASD without intellectual disability. The present study adds to the growing body of evidence, encompassing both animal and human studies, that supports possible immune-mediated mechanisms underlying the etiology of ASD.

Maternal folate status as a risk factor for autism spectrum disorders: a review of existing evidence.

Emerging evidence from epidemiological studies supports the notion that maternal folate status regulated by dietary and genetic factors early in pregnancy may influence the risk of autism spectrum disorders (ASD). In this review, we provide an overview of what is known about the role of folate in the aetiology of neurodevelopmental disorders; summarise relevant biological, genetic and epigenetic mechanisms; and synthesise the evidence from human observational studies and randomised controlled trials that have examined the relationship between maternal folate and ASD or related traits. Much of the existing literature on this topic is subject to limitations such as potential confounding by healthy behaviours and other dietary factors, and exposure assessed within limited exposure windows. As the existing evidence is inconclusive, further research remains to be conducted in order to verify this hypothesis. Complete assessment of maternal functional folate status through the pre- and peri-conceptional periods requires biological measurement of folate, vitamin B12 and homocysteine and genetic variants involved in one-carbon metabolism and epigenetic mechanisms. In addition to more complete assessment of maternal functional folate status, careful consideration of potential confounding is warranted.

Maternal Steroid Hormone Levels in Early Pregnancy and Autism in the Offspring: A Population-Based, Nested Case-Control Study.

BACKGROUND: A role for prenatal steroid hormones in the etiology of autism has been proposed, but evidence is conflicting. METHODS: Here, we examined serum levels of maternal estradiol, testosterone, 17-hydroxyprogesterone (OHP), and cortisol from the first trimester of gestation (mean = 10.1 weeks) in relation to the odds of diagnosed autism with and without co-occurring intellectual disability (ID) in the offspring (n = 118 autism with ID, n = 249 autism without ID, n = 477 control). Levels of maternal hormones were measured using highly sensitive liquid chromatography tandem mass spectrometry, standardized according to gestational timing of sample collection, and analyzed with restricted cubic spline logistic regression models adjusting for child's sex and maternal health, demographic, and socioeconomic factors. RESULTS: We observed significant nonlinear associations between maternal estradiol, 17-OHP, and cortisol with autism, which varied with the presence of co-occurring ID. Compared to mean levels, lower levels of estradiol were associated with higher odds of autism with ID (odds ratio for concentrations 1 SD below the mean = 1.66; 95% CI, 1.24-2.11), while higher cortisol levels were associated with lower odds (odds ratio for 1 SD above the mean = 0.55; 95% CI, 0.36-0.88). In contrast, higher 17-OHP was associated with increased odds of autism without ID (odds ratio for 1 SD above the mean = 1.49; 95% CI, 1.11-1.99). We observed no evidence for interaction with sex of the child. CONCLUSIONS: These findings support the notion that the maternal steroid hormonal environment in early pregnancy may contribute to autism, but also emphasize the complex relationship between early-life steroid exposure and autism.

Environmental exposure to metals and children's growth to age 5 years: a prospective cohort study.

In this prospective cohort study, based on 1,505 mother-infant pairs in rural Bangladesh, we evaluated the associations between early-life exposure to arsenic, cadmium, and lead, assessed via concentrations in maternal and child urine, and children's weights and heights up to age 5 years, during the period 2001-2009. Concurrent and prenatal exposures were evaluated using linear regression analysis, while longitudinal exposure was assessed using mixed-effects linear regression. An inverse association was found between children's weight and height, age-adjusted z scores, and growth velocity at age 5 years and concurrent exposure to cadmium and arsenic. In the longitudinal analysis, multivariable-adjusted attributable differences in children's weight at age 5 years were -0.33 kg (95% confidence interval (CI): -0.60, -0.06) for high (≥95th percentile) arsenic exposure and -0.57 kg (95% CI: -0.88, -0.26) for high cadmium exposure, in comparison with children with the lowest exposure (≤5th percentile). Multivariable-adjusted attributable differences in height were -0.50 cm (95% CI: -1.20, 0.21) for high arsenic exposure and -1.6 cm (95% CI: -2.4, -0.77) for high cadmium exposure. The associations were apparent primarily among girls. The negative effects on children's growth at age 5 years attributable to arsenic and cadmium were of similar magnitude to the difference between girls and boys in terms of weight (-0.67 kg, 95% CI: -0.82, -0.53) and height (-1.3 cm, 95% CI: -1.7, -0.89).

Pregnancy and the methyltransferase genotype independently influence the arsenic methylation phenotype.

OBJECTIVES: The methyltransferase genotype and pregnancy both influence the arsenic metabolism phenotype, but it is unknown whether these factors interact, explaining the drastic changes in the efficiency of arsenic metabolism observed among pregnant women. The aim of this study was to evaluate the relative contribution of the methyltransferase genotype and pregnancy to the arsenic metabolism phenotype. METHODS: We studied longitudinally the arsenic metabolite pattern in urine (at approximately gestational weeks 8, 14, and 30) of 303 women exposed to arsenic through drinking water and food in rural Bangladesh. Urinary arsenic metabolites were measured by high-performance liquid chromatography-inductively coupled plasma mass spectrometry. Data were available on genotypes for 16 polymorphisms, combined as haplotypes, in three methyltransferases: arsenic(+III)methyltransferase (AS3MT) and DNA-methyltransferases 1a and 3b (DNMT1a and DNMT3b). Changes in the arsenic metabolite pattern over time were evaluated by haplotype using logistic quantile regression. RESULTS: All four AS3MT haplotypes and all three DNMT1a haplotypes significantly influenced the metabolite pattern in the pregnant women, with consistent effects of genotype over the entire course of pregnancy. No interaction was found between the haplotypes and pregnancy-related changes in the arsenic metabolism phenotype. DNMT3b haplotypes did not significantly influence the metabolite pattern. We observed a pregnancy-attributable decrease of 5.7% in the most risk-associated monomethylated metabolite, methylarsonic acid, whereas changes between 1.6 and 5.3% of methylarsonic acid could be attributed to haplotypes of AS3MT and DNMT1a. CONCLUSION: Independent of the genotype, the efficiency of arsenic methylation increased markedly over the course of pregnancy. The effect of pregnancy on the metabolite pattern during the observational period was greater than the effect of genotype.

Maternal Levels of Cytokines in Early Pregnancy and Risk of Autism Spectrum Disorders in Offspring.

Previous studies indicate a role of immune disturbances during early development in the etiology of autism spectrum disorders (ASD). Any potential disturbances during fetal development are best addressed by prospective evaluation of maternal markers of inflammation. Previous studies have investigated maternal cytokines, a group of powerful effectors of the immune system, with inconsistent results. In this study, we aimed to clarify the relationship between maternal cytokines and ASD by evaluating levels of 17 cytokines in first trimester maternal serum samples, from 318 mothers to ASD-cases and 429 mothers to ASD-unaffected controls, nested within the register-based Stockholm Youth Cohort. Overall, we observed no consistent associations between levels of maternal cytokines and ASD. While we observed a number of individual associations, the patterns varied across the diagnostic sub-groups. Levels above the 90th percentile of IL-1ß (OR = 2.31, 95% CI 1.16-4.60), IL-7 (OR = 2.28, 95% CI 1.20-4.33), IL-13 (OR = 2.42, 95% CI 1.29-4.55), and MCP-1 (OR = 2.09, 95% CI 1.03-4.24) were associated with increased odds of ASD with co-occurring intellectual disability (ID), whereas GMCSF (OR = 2.06, 95% CI 1.03-4.11) and TNF-α (OR = 2.31, 95% CI 1.18-4.50) were associated with increased odds of ASD with ADHD but none survived correction for multiple comparisons. Also, none of the measured maternal cytokines were associated with ASD without co-occurring ID or ADHD. Implementing a data-driven approach using machine learning (Random Forest's Variable Importance measurement), we found no evidence to suggest that adding these cytokines and other markers of maternal immunity, to register-based maternal factors (e.g., psychiatric history) improves prediction of ASD. In summary, we found no robust evidence of an association between maternal immune markers during early pregnancy and ASD.

Maternal infection during pregnancy and likelihood of autism and intellectual disability in children in Sweden: a negative control and sibling comparison cohort study.

BACKGROUND: Maternal infections during pregnancy are associated with intellectual disability and autism in exposed children. Whether these associations are causal, and therefore should be targets of preventive strategies, remains unknown. We aimed to investigate these associations, to determine whether there is a causal role of maternal infection during pregnancy for children's risk of autism and intellectual disability, by accounting for unmeasured familial factors. METHODS: We used a register-based cohort study design, and included children living in Stockholm County, Sweden, who were born in 1987-2010. We excluded children not born in Sweden, adopted children, and children with unknown biological mothers or fathers. Maternal infections during pregnancy, defined by ICD-8, ICD-9, and ICD-10 codes, were identified in the National Patient Register and Medical Birth Register. Children were followed up from birth to an outcome or a censoring event (death, migration from Stockholm, age 18 years, or Dec 31, 2016, whichever occurred first). The primary outcomes were diagnosis of autism or diagnosis of intellectual disability. We did a survival analysis to examine the association between inpatient and outpatient specialised care for any infection during pregnancy and likelihood of autism or intellectual disability in the child. To address potential residual confounding, we also estimated the relationship between maternal infection in the year preceding pregnancy as a negative control exposure and conducted a matched sibling analysis of sibling pairs who were discordant for autism or intellectual disability. FINDINGS: 647 947 children living in Stockholm County were identified and, after excluding 97 980 children, we included 549 967 in the study (267 995 [48·7%] were female and 281 972 [51·3%] were male; mean age at censoring 13·5 years [SD 5·0; range <1 to 18]; 142 597 [25·9%] had a mother who was not born in Sweden). 445 (1·3%) of 34 013 children exposed to maternal infection during pregnancy were diagnosed with intellectual disability and 1123 (3·3%) with autism. 5087 (1·0%) of 515 954 unexposed children were diagnosed with intellectual disability and 13 035 (2·5%) with autism. Maternal infection during pregnancy was associated with autism (hazard ratio [HR] 1·16, 95% CI 1·09-1·23) and intellectual disability (1·37, 1·23-1·51) in exposed children compared with unexposed children. Maternal infection in the year before pregnancy (negative control exposure) was also associated with autism (HR 1·25, 95% CI 1·14-1·36), but was not associated with intellectual disability (1·09, 0·94-1·27). In sibling comparisons, the associations with maternal infection during pregnancy were attenuated for autism (HR 0·94, 95% CI 0·82-1·08; n=21 864), but not to the same extent for intellectual disability (1·15, 0·95-1·40; n=9275). INTERPRETATION: Although infections in pregnant women are associated with both autism and intellectual disability in their children, the association with autism does not appear to reflect a causal relationship, but is more likely to be explained by factors shared between family members such as genetic variation or aspects of the shared environment. Thus, infection prevention is not expected to reduce autism incidence. For intellectual disability, unmeasured familial factors might not fully explain the observed associations, and a causal role of maternal infections cannot be excluded. Causal effects of specific but rare infections or infections not requiring health care contact cannot be excluded in either autism or intellectual disability. FUNDING: Swedish Research Council, Stanley Medical Research Institute, and Autism Speaks. TRANSLATION: For the Swedish translation of the abstract see Supplementary Materials section.

Parental inflammatory bowel disease and autism in children.

Evidence linking parental inflammatory bowel disease (IBD) with autism in children is inconclusive. We conducted four complementary studies to investigate associations between parental IBD and autism in children, and elucidated their underlying etiology. Conducting a nationwide population-based cohort study using Swedish registers, we found evidence of associations between parental diagnoses of IBD and autism in children. Polygenic risk score analyses of the Avon Longitudinal Study of Parents and Children suggested associations between maternal genetic liability to IBD and autistic traits in children. Two-sample Mendelian randomization analyses provided evidence of a potential causal effect of genetic liability to IBD, especially ulcerative colitis, on autism. Linkage disequilibrium score regression did not indicate a genetic correlation between IBD and autism. Triangulating evidence from these four complementary approaches, we found evidence of a potential causal link between parental, particularly maternal, IBD and autism in children. Perinatal immune dysregulation, micronutrient malabsorption and anemia may be implicated.

Neonatal Levels of Acute Phase Proteins and Risk of Autism Spectrum Disorder.

BACKGROUND: Immune signaling pathways influence neurodevelopment and are hypothesized to contribute to the etiology of autism spectrum disorder (ASD). We aimed to assess risk of ASD in relation to levels of neonatal acute phase proteins (APPs), key components of innate immune function, measured in neonatal dried blood spots. METHODS: We included 924 ASD cases, 1092 unaffected population-based controls, and 203 unaffected siblings of ASD cases in this case-control study nested within the register-based Stockholm Youth Cohort. Concentrations of 9 different APPs were measured in eluates from neonatal dried blood spots from cases, controls, and siblings using a bead-based multiplex assay. RESULTS: Neonatal C-reactive protein was consistently associated with odds of ASD in case-control comparisons, with higher odds associated with the highest quintile compared with the middle quintile (odds ratio [OR] = 1.50, 95% confidence interval [CI] = 1.10-2.04) in adjusted analyses. In contrast, the lowest quintiles of α-2-macroglobulin (OR = 3.71, CI = 1.21-11.33), ferritin (OR = 4.20, CI = 1.40-12.65), and serum amyloid P (OR = 3.05, CI = 1.16-8.01) were associated with odds of ASD in the matched sibling comparison. Neonatal APPs varied with perinatal environmental factors and maternal/fetal phenotypes. Significant interactions in terms of risk for ASD were observed between neonatal APPs and maternal infection during late pregnancy, maternal anemia, and maternal psychiatric history. CONCLUSIONS: Indicators of the neonatal innate immune response are associated with risk of ASD, although the nature of these associations varies considerably with factors in the perinatal environment and the genetic background of the comparison group.

Maternal antibodies to gliadin and autism spectrum disorders in offspring-A population-based case-control study in Sweden.

While individuals diagnosed with autism spectrum disorders (ASD) have higher levels of antibodies directed towards gliadin, a component of wheat gluten, no study has examined anti-gliadin antibodies (AGA) in etiologically relevant periods before diagnosis. The objective of this study was to investigate if maternal levels of AGA, during pregnancy and at the time of birth, are associated with ASD in offspring. We analyzed AGA in archived neonatal dried blood spots (NDBS) for 921 ASD cases and 1090 controls, and in paired maternal sera collected earlier in pregnancy for a subset of 547 cases and 428 controls. We examined associations with ASD diagnoses as a group and considering common comorbidities (intellectual disability [ID] and attention-deficit/hyperactivity disorder). We compared 206 cases to their unaffected siblings to examine the potential for confounding by shared familial factors. Odds of ASD tended to be lower among those with the highest levels (≥90th percentile) of AGA compared to those with low levels (<80th percentile; OR 0.78, 95% CI 0.56-1.09, measured in NDBS). This pattern was more apparent for ASD with comorbid ID when measured in NDBS (0.51, 0.30-0.87), with a similar trend in maternal sera (0.55, 0.24-1.29). High levels of AGA were similarly associated with lower odds of ASD in the sibling comparison. In summary, we found little association between maternal antibodies raised against components of gluten and risk of ASD in general. Exposure to high levels of AGA in the pre- and perinatal periods may be protective in terms of risk for ASD with ID. LAY SUMMARY: There is a debate among both scientists and community members as to whether an immune reaction to gluten exposure could be considered a cause of autism. We examined antibodies that are directed against gliadin, a part of gluten, in samples collected from pregnant mothers and their newborn babies. We did not see any major differences in the antibody level among those children diagnosed with ASD or their mothers compared to children who were not diagnosed with ASD. High levels of the antibodies were in fact associated with a somewhat lower risk of ASD with co-occurring intellectual disabilities, though we cannot tell from this study why that might be the case.

Mercury exposure, serum antinuclear/antinucleolar antibodies, and serum cytokine levels in mining populations in Amazonian Brazil: a cross-sectional study.

Mercury is an immunotoxic substance that has been shown to induce autoimmune disease in rodent models, characterized by lymphoproliferation, overproduction of immunoglobulin (IgG and IgE), and high circulating levels of auto-antibodies directed at antigens located in the nucleus (antinuclear auto-antibodies, or ANA) or the nucleolus (antinucleolar auto-antibodies, or ANoA). We have reported elevated levels of ANA and ANoA in human populations exposed to mercury in artisanal gold mining, though other confounding variables that may also modulate ANA/ANoA levels were not well controlled. The goal of this study is to specifically test whether occupational and environmental conditions (other than mercury exposure) that are associated with artisanal gold mining affect the prevalence of markers of autoimmune dysfunction. We measured ANA, ANoA, and cytokine concentrations in serum and compared results from mercury-exposed artisanal gold miners to those from diamond and emerald miners working under similar conditions and with similar socio-economic status and risks of infectious disease. Mercury-exposed gold miners had higher prevalence of detectable ANA and ANoA and higher titers of ANA and ANoA as compared to diamond and emerald miners with no occupational mercury exposure. Also, mercury-exposed gold miners with detectable ANA or ANoA in serum had significantly higher concentrations of pro-inflammatory cytokines IL-1beta, TNF-alpha, and IFN-gamma in serum as compared to the diamond and emerald miners. This study provides further evidence that mercury exposure may lead to autoimmune dysfunction and systemic inflammation in affected populations.

The Association of Paternal IQ With Autism Spectrum Disorders and Its Comorbidities: A Population-Based Cohort Study.

OBJECTIVE: Original case descriptions of autism noted that parents of the affected children tended to be highly educated and intelligent, a characterization that has endured publicly. Recent genetic studies indicate that risk for autism spectrum disorders (ASD) is associated with high intelligence. We examined the association between paternal intelligence and ASD, considering co-occurring intellectual disability (ID) and attention-deficit/hyperactivity disorder (ADHD). METHOD: We used a register-based cohort study design including 360,151 individuals with fathers conscripted to the Swedish military, resident in Stockholm, Sweden, born from 1984 to 2008, and followed until December 31, 2011, for diagnosis of ASD, ADHD, and/or ID. Risk of neurodevelopmental disorders relative to paternal IQ (rated on a 9-point scale) was assessed using a score of 5 (average intelligence) as the referent in models accounting for potentially nonlinear relationships and clustering of siblings. RESULTS: We observed an association between high paternal IQ and offspring risk of ASD without ID/ADHD in models adjusted for individual and family characteristics (ORIQ=9 1.32, 95% CI 1.15-1.52), an association that appeared to be driven largely by the fathers' score on the technical comprehension portion of the test (ORTechnical IQ = 9 1.53, 95% CI 1.31-1.78). Conversely, low paternal IQ was associated with ASD+ID (ORIQ = 11.78, 95% CI 1.27-2.49) and ASD+ADHD (ORIQ = 11.40, 95% CI 1.16-1.70); low paternal IQ was strongly associated with ID (ORIQ = 1 4.46, 95% CI 3.62-5.49) and present also for ADHD (ORIQ = 11.56, 95% CI 1.42-1.72)] without co-occurring ASD or ID. CONCLUSION: The relationship between paternal IQ and offspring risk of ASD was nonmonotonic and varied by the presence of co-occurring disorders, probably reflecting phenotypic diversity among affected individuals.

The Familial Risk of Autism Spectrum Disorder with and without Intellectual Disability.

Autism spectrum disorder (ASD) is highly heritable, yet how its familial risk and heritability may vary by cognitive ability is not well understood. In this population-based cohort study, we examined the familial risk and heritability of ASD with and without co-occurring intellectual disability (ID). We estimated odds ratios and heritability of ASD with ID (ASD+ID) and ASD without ID (ASD-ID) using register-based diagnosis data of 567,436 index persons born in 1984-2009 in Stockholm County, Sweden, and their parents, siblings, cousins, aunts, and uncles. The familial risk profile exhibited differences between ASD-ID and ASD+ID, most notably for index persons with affected parents. For example, for an index person who had at least one parent with ASD, the child's odds of ASD-ID and ASD+ID (95% confidence interval (CI)) increased by 16.2 (14.2-18.6) and 7.4 (5.5-10.0) folds, respectively. The more closely related a family member with ASD was, the greater the observed risk was of ASD in the index person, especially for ASD-ID. The broad-sense heritability (95% CI) for ASD - ID and ASD+ID were 64.6% (46.0-100.0%) and 33.4% (14.4-58.4%), respectively. Familial risk and heritability of ASD may vary by intellectual ability, which implies that risk factors between these ASD phenotypes may differ. Our findings from the heritability analysis and familial risk analysis suggest that ASD-ID may have a greater genetic basis than ASD+ID, although this should be verified in future studies. LAY SUMMARY: Autism spectrum disorder (ASD) is highly heritable, yet how its familial risk and heritability may vary by cognitive ability is not well-understood. In a population-based cohort study on families of 567,436 index persons using Swedish registers data, we found that the familial risk profile differed between ASD with and without intellectual disability. Our findings from the heritability analysis and familial risk analysis suggest that ASD-ID may have a greater genetic basis than ASD+ID, although this should be verified in future studies.