National Birth Defects Prevention Study Research Articles

Short interpregnancy intervals and risks for birth defects: support for the nutritional depletion hypothesis

Research suggests short interpregnancy intervals increase risks for adverse perinatal outcomes, including some birth defects. A hypothesized cause is nutritional depletion, including folic acid (FA). We evaluated associations between short interpregnancy intervals, alone and in combination with FA intake, and the occurrence of select malformations. Data were from the National Birth Defects Prevention Study (US case-control, 1997-2011). Participants included multiparous women whose prior pregnancy resulted in live birth. Cases included 8 noncardiac and 6 cardiac defect groups (n=3219); controls were nonmalformed live-borns (n=2508). We categorized interpregnancy interval (<6, 6-11, 12-17, and 18-23 mo) and periconceptional FA intake [no FA supplement use and dietary folate equivalents (DFE) <400 µg/d, no FA supplement use and DFE ≥400 µg/d, or any FA supplement use]. We controlled for age, race/ethnicity, income, pregnancy intention, and study center. ORs <0.8 or >1.2 were considered to represent potentially meaningful associations. ORs for <6 compared with 18-23 mo were >1.2 for 4/8 noncardiac and 3/6 cardiac malformations. Among participants with any FA supplement use, ORs comparing <6 with 6-23 mo were <1.2 for most defects. Conversely, most ORs were >1.2 for <6 mo+no FA supplement use and DFE <400 µg/d compared with 6-23 mo+any FA supplement use. Magnitude and precision varied by defect. Short interpregnancy intervals were associated with a trend of higher risks for several defects, notably in the absence of FA supplement use. To our knowledge, our study is the first to provide preliminary empirical support that these etiologies may be related to shorter interpregnancy intervals and possible nutritional deficiencies. Because FA intake is highly correlated with other nutrients, and because our estimates were generally imprecise, more research with larger sample sizes is needed to better understand the role of FA compared with other nutrients in each defect-specific etiology.

Testing and Validating Semi-automated Approaches to the Occupational Exposure Assessment of Polycyclic Aromatic Hydrocarbons.

When it is not possible to capture direct measures of occupational exposure or conduct biomonitoring, retrospective exposure assessment methods are often used. Among the common retrospective assessment methods, assigning exposure estimates by multiple expert rater review of detailed job descriptions is typically the most valid, but also the most time-consuming and expensive. Development of screening protocols to prioritize a subset of jobs for expert rater review can reduce the exposure assessment cost and time requirement, but there is often little data with which to evaluate different screening approaches. We used existing job-by-job exposure assessment data (assigned by consensus between multiple expert raters) from a large, population-based study of women to create and test screening algorithms for polycyclic aromatic hydrocarbons (PAHs) that would be suitable for use in other population-based studies. We evaluated three approaches to creating a screening algorithm: a machine-learning algorithm, a set of a priori decision rules created by experts based on features (such as keywords) found in the job description, and a hybrid algorithm incorporating both sets of criteria. All coded jobs held by mothers of infants participating in National Birth Defects Prevention Study (NBDPS) (n = 35,424) were used in developing or testing the screening algorithms. The job narrative fields considered for all approaches included job title, type of product made by the company, main activities or duties, and chemicals or substances handled. Each screening approach was evaluated against the consensus rating of two or more expert raters. The machine-learning algorithm considered over 30,000 keywords and industry/occupation codes (separate and in combination). Overall, the hybrid method had a similar sensitivity (87.1%) as the expert decision rules (85.5%) but was higher than the machine-learning algorithm (67.7%). Specificity was best in the machine-learning algorithm (98.1%), compared to the expert decision rules (89.2%) and hybrid approach (89.1%). Using different probability cutoffs in the hybrid approach resulted in improvements in sensitivity (24-30%), without the loss of much specificity (7-18%). Both expert decision rules and the machine-learning algorithm performed reasonably well in identifying the majority of jobs with potential exposure to PAHs. The hybrid screening approach demonstrated that by reviewing approximately 20% of the total jobs, it could identify 87% of all jobs exposed to PAHs; sensitivity could be further increased, albeit with a decrease in specificity, by adjusting the algorithm. The resulting screening algorithm could be applied to other population-based studies of women. The process of developing the algorithm also provides a useful illustration of the strengths and potential pitfalls of these approaches to developing exposure assessment algorithms.

Modification of the association between diabetes and birth defects by obesity, National Birth Defects Prevention Study, 1997-2011.

Maternal pregestational diabetes and obesity are risk factors for birth defects. Diabetes and obesity often occur together; it is unclear whether their co-occurrence compounds birth defect risk. We analyzed 1997-2011 data on 29,671 cases and 10,963 controls from the National Birth Defects Prevention Study, a multisite case-control study. Mothers self-reported height, pregestational weight, and diabetes (pregestational and gestational; analyzed separately). We created four exposure groups: no obesity or diabetes (referent), obesity only, diabetes only, and both obesity and diabetes. We estimated odds ratios (ORs) using logistic regression and the relative excess risk due to interaction (RERI). Among mothers with pregestational obesity without diabetes, modest associations (OR range: 1.1-1.5) were observed for neural tube defects, small intestinal atresia, anorectal atresia, renal agenesis/hypoplasia, omphalocele, and several congenital heart defects. Pregestational diabetes, regardless of obesity, was strongly associated with most birth defects (OR range: 2.0-75.9). Gestational diabetes and obesity had a stronger association than for obesity alone and the RERI (in parentheses) suggested additive interaction for hydrocephaly (1.2; 95% confidence interval [CI]: -0.1, 2.5), tetralogy of Fallot (0.9; 95% CI: -0.01, 1.8), atrioventricular septal defect (1.1; 95% CI: -0.1, 2.3), hypoplastic left heart syndrome (1.1; 95% CI: -0.2, 2.4), and atrial septal defect secundum or not otherwise specified (1.0; 95% CI: 0.3, 1.6; only statistically significant RERI). Our results do not support a synergistic relationship between obesity and diabetes for most birth defects examined. However, there are opportunities for prevention by reducing obesity and improving glycemic control among women with pregestational diabetes before conception.

Paternal genetic variants and risk of obstructive heart defects: A parent-of-origin approach.

Previous research on risk factors for obstructive heart defects (OHDs) focused on maternal and infant genetic variants, prenatal environmental exposures, and their potential interaction effects. Less is known about the role of paternal genetic variants or environmental exposures and risk of OHDs. We examined parent-of-origin effects in transmission of alleles in the folate, homocysteine, or transsulfuration pathway genes on OHD occurrence in offspring. We used data on 569 families of liveborn infants with OHDs born between October 1997 and August 2008 from the National Birth Defects Prevention Study to conduct a family-based case-only study. Maternal, paternal, and infant DNA were genotyped using an Illumina Golden Gate custom single nucleotide polymorphism (SNP) panel. Relative risks (RR), 95% confidence interval (CI), and likelihood ratio tests from log-linear models were used to estimate the parent-of-origin effect of 877 SNPs in 60 candidate genes in the folate, homocysteine, and transsulfuration pathways on the risk of OHDs. Bonferroni correction was applied for multiple testing. We identified 3 SNPs in the transsulfuration pathway and 1 SNP in the folate pathway that were statistically significant after Bonferroni correction. Among infants who inherited paternally-derived copies of the G allele for rs6812588 in the RFC1 gene, the G allele for rs1762430 in the MGMT gene, and the A allele for rs9296695 and rs4712023 in the GSTA3 gene, RRs for OHD were 0.11 (95% CI: 0.04, 0.29, P = 9.16x10-7), 0.30 (95% CI: 0.17, 0.53, P = 9.80x10-6), 0.34 (95% CI: 0.20, 0.57, P = 2.28x10-5), and 0.34 (95% CI: 0.20, 0.58, P = 3.77x10-5), respectively, compared to infants who inherited maternally-derived copies of the same alleles. We observed statistically significant decreased risk of OHDs among infants who inherited paternal gene variants involved in folate and transsulfuration pathways.

Prepregnancy body mass index and spina bifida: Potential contributions of bias.

Epidemiologists have consistently observed associations between prepregnancy obesity and spina bifida in offspring. Most studies, however, used self-reported body mass index (potential for exposure misclassification) and incompletely ascertained cases of spina bifida among terminations of pregnancy (potential for selection bias). We conducted a quantitative bias analysis to explore the potential effects of these biases on study results. We included 808 mothers of fetuses or infants with spina bifida (case mothers) and 7,685 mothers of infants without birth defects (control mothers) from a population-based case-control study, the National Birth Defects Prevention Study (1997-2011). First, we performed a conventional epidemiologic analysis, adjusting for potential confounders using logistic regression. Then, we used 5,000 iterations of probabilistic bias analysis to adjust for the combination of confounding, exposure misclassification, and selection bias. In the conventional confounding-adjusted analysis, prepregnancy obesity was associated with spina bifida (odds ratio 1.4, 95% confidence interval: 1.2, 1.7). In the probabilistic bias analysis, we tested nine different models for the combined effects of confounding, exposure misclassification, and selection bias. Results were consistent with a weak to moderate association between prepregnancy obesity and spina bifida, with the median odds ratios across the nine models ranging from 1.1 to 1.4. Given our assumptions about the occurrence of bias in the study, our results suggest that exposure misclassification, selection bias, and confounding do not completely explain the association between prepregnancy obesity and spina bifida.

Maternal Exposure to Disinfection By-Products and Risk of Hypospadias in the National Birth Defects Prevention Study (2000-2005).

The purpose of this study was to estimate the association between 2nd and 3rd degree hypospadias and maternal exposure to disinfection by-products (DBPs) using data from a large case-control study in the United States. Concentration estimates for total trihalomethanes (TTHMs), the sum of the five most prevalent haloacetic acids (HAA5), and individual species of each were integrated with data on maternal behaviors related to water-use from the National Birth Defects Prevention Study (NBDPS) to create three different exposure metrics: (1) household DBP concentrations; (2) estimates of DBP ingestion; (3) predicted uptake (i.e., internal dose) of trihalomethanes (THMs) via ingestion, showering, and bathing. The distribution of DBP exposure was categorized as follows: (Q1/referent) < 50%; (Q2) ≥ 50% to < 75%; and (Q3) ≥ 75%. Logistic regression was used to estimate adjusted odds ratios (aORs) and 95% confidence intervals (CIs). Generally, null associations were observed with increasing TTHM or HAA5 exposure. An increased risk was observed among women with household bromodichloromethane levels in the second quantile (aOR: 1.8; 95% CI: 1.2, 2.7); however, this association did not persist after the inclusion of individual-level water-use data. Findings from the present study do not support the hypothesis that maternal DBP exposures are related to the occurrence of hypospadias.

Abstract 16552: Chromosomal Microarray Abnormalities in More Than 1300 Patients With Congenital Heart Disease Provide Novel Clinical and Etiological Insights

Introduction: The genetic basis of congenital heart disease (CHD) is incompletely understood. Approximately 10-20% of infants with CHD have abnormal chromosome microarray (CMA) results, however, the spectrum of genomic and phenotypic abnormalities remains incompletely characterized. Methods: All study patients had abnormal CMA on clinical testing and abnormal cardiac findings on echocardiogram, as identified at 9 pediatric cardiac centers. Clinical genetic testing results, diagnoses, and echocardiogram reports for detailed cardiac phenotyping were collected. CMA results were denoted as abnormal for any reported findings that included copy number variants (CNVs) and/or regions of homozygosity. Cardiac classification was performed with minor modification to National Birth Defect Prevention Study methods. Recurrent CNVs were identified algorithmically. Functional enrichment analysis of genes predicted to be intolerant of loss-of-function (LOF) in CNVs and genes located in monogenic CNVs was performed using ToppGene. Results: The study included 1369 patients. Genetic syndromes highly associated with CHD such as Trisomy 21, Turner syndrome, and 22q11.2 deletion syndrome among others were identified in 401 patients and elucidated less recognized cardiac phenotypes in these groups. Analyzing genes known to be causative of CHD in the remaining patients (N=968) showed enrichment in CNVs &lt; 5 megabases (N=51; 7%). Common recurrent loci included duplications in 15q13.2-13.3 (N=16 patients) and 16p11.13 (N=12; 8 with left-sided cardiac lesion), and deletions in 15q11.2 (N=14; 6 with total anomalous pulmonary venous return) and 2q13 (N=10; 8 with conotruncal defect). Genes predicted to be intolerant of LOF (495 genes) or located in monogenic CNVs (137 genes) were enriched for neuronal processes. Conclusions: The consortium provides the largest data set of abnormal clinical CMA results in patients with detailed CHD phenotyping to our knowledge. The findings provide novel understanding of CHD phenotypes, a roadmap of recurrent loci, and pathways and candidate genes in CNV-associated CHD. The consortium’s data will lead to improved genetic understanding and clinical care of patients with CHD.

Study links individual antidepressants used early in pregnancy to birth defects

An analysis of data from the National Birth Defects Prevention Study has uncovered some associations between maternal use of antidepressants and heightened risk of birth defects, with venlafaxine linked to the highest prevalence of birth defects. The study did not fully account for potential confounding by underlying condition, however, because the data set did not include information about mothers' psychiatric diagnoses. Results were published online Aug. 5 in JAMA Psychiatry.

Polycyclic Aromatic Hydrocarbons and Birth Defects in California

Background: Ambient air pollution has been associated with several birth defects, though few studies have examined polycyclic aromatic hydrocarbons (PAHs), specifically. Our aim was to assess the relationship between maternal exposure to ambient PAHs in the first two months of pregnancy and risk of several structural birth defects as part of the Berkeley-Stanford Children’s Environmental Health Center (Children’s Health and Air Pollution Study).Methods: PAHs were assessed through a combination of intermittent monitoring and estimated PAH concentrations based on daily, collected NO and CO measurements in the San Joaquin Valley of California. Daily exposure values were spatially interpolated from the air quality monitoring stations’ locations to women’s residence locations in early pregnancy using inverse distance-squared weighting with a maximum interpolation radius of 25 km. We used data from 1028 cases and 975 controls from the California center of the National Birth Defects Prevention Study (1997-2011) to examine quartiles of exposure to risk of neural tube defects (N=281), gastroschisis (N=223), and cleft lip with or without cleft palate (N=364) or cleft palate only (N=162). Models were adjusted for maternal race/ethnicity, education and vitamin use in early pregnancy. Results: We found suggestive associations between PAHs and neural tube defects including spina bifida and anencephaly with evidence of an exposure-response across quartiles of PAHs. High ambient PAHs during the first two months of pregnancy were associated with a small increased risk of neural tube defects [odds ratio (OR)=1.23; 95% confidence interval (CI):0.83, 1.82]. We found inverse associations between PAHs and risk of gastroschisis (OR=0.58; 95% CI:0.37, 0.90) and cleft lip with or without cleft palate (OR=0.66; 95% CI:0.46, 0.95).Conclusions: Some results were in the unexpected direction, but results are consistent with our previous observed associations between other traffic-related air pollutants and neural tube defects in the San Joaquin Valley of California.

Periconceptional stressors and social support and risk for adverse birth outcomes

BackgroundThe prevalence of preterm birth and low birth weight has been increasing slightly in recent years. A few studies have suggested that psychosocial stress during pregnancy may increase risk for these adverse birth outcomes. To extend those observations, we analyzed various major life event stressors separately and cumulatively as potential risk factors for preterm birth and low birth weight using granular categories of each outcome in a large, population-based study. Additionally, we assessed if greater social support buffered any effects.MethodsData were from a nested prevalence study of 4395 women in the National Birth Defects Prevention Study who delivered live-born non-malformed infants (controls) between 2006 and 2011. Participants completed a standardized, computer-assisted interview between 6 weeks and 24 months after delivery that included questions on stress and social support from 3 months before pregnancy to the 3rd month of pregnancy. Cumulative stress and support indices were also calculated. Preterm birth was divided into “early preterm” (< 32 weeks), “late preterm” (32–36 weeks) and “term.” Low birthweight was divided into “very low birth weight” (< 1500 g), “low birth weight” (1500–2499 g) and “normal birth weight” (≥2500 g). Relative risks and 95% confidence intervals (95% CI) were calculated using Poisson regression.ResultsFor women reporting relationship difficulties, there was a suggestive risk of early preterm birth (RR: 1.9, 95%CI: 0.9–3.9) and very low birthweight (RR: 2.0, 95%CI: 0.9–4.4). For women reporting that they or someone close to them were victims of abuse, violence, or crime, there was an increased risk of low birthweight (RR: 1.8, 95%CI: 1.1–2.7) and late preterm birth (RR: 1.5, 95%CI: 1.0–2.2). There were no strong associations observed between social support questions and the various outcomes.ConclusionsOur results add some support to prior evidence that certain stressors may be associated with increase selected adverse birth outcomes risk. We did not find strong evidence that social support buffered the observed risks in our study.

Maternal Use of Specific Antidepressant Medications During Early Pregnancy and the Risk of Selected Birth Defects

Antidepressants are commonly used during pregnancy, but limited information is available about individual antidepressants and specific birth defect risks. To examine associations between individual antidepressants and specific birth defects with and without attempts to partially account for potential confounding by underlying conditions. The population-based, multicenter case-control National Birth Defects Prevention Study (October 1997-December 2011) included cases with selected birth defects who were identified from surveillance systems; controls were randomly sampled live-born infants without major birth defects. Mothers of cases and controls participated in an interview after the expected delivery date. The data were analyzed after the completion of the National Birth Defects Prevent Study's data collection. Self-reported antidepressant exposure was coded to indicate monotherapy exposure to antidepressants. We used multivariable logistic regression to calculate adjusted odds ratios (aORs) and 95% confidence intervals for associations between maternal antidepressant use and birth defects. We compared early pregnancy antidepressant-exposed women with those without antidepressant exposure and, to partially account for confounding by underlying maternal conditions, those exposed to antidepressants outside of the birth defect development critical period. This study included 30 630 case mothers of infants with birth defects and 11 478 control mothers (aged 12-53 years). Early pregnancy antidepressant use was reported by 1562 case mothers (5.1%) and 467 control mothers (4.1%), for whom elevated aORs were observed for individual selective serotonin reuptake inhibitors (SSRIs) and selected congenital heart defects (CHD) (eg, fluoxetine and anomalous pulmonary venous return: aOR, 2.56; 95% CI, 1.10-5.93; this association was attenuated after partially accounting for underlying conditions: aOR, 1.89; 95% CI, 0.56-6.42). This pattern was observed for many SSRI-CHD combinations. Associations between SSRIs and non-CHD birth defects often persisted or strengthened after partially accounting for underlying conditions (eg, citalopram and diaphragmatic hernia: aOR, 5.11; 95% CI, 1.29-20.24). Venlafaxine had elevated associations with multiple defects that persisted after partially accounting for underlying conditions (eg, anencephaly and craniorachischisis: aOR, 9.14; 95% CI, 1.91-43.83). We found some associations between maternal antidepressant use and specific birth defects. Venlafaxine was associated with the highest number of defects, which needs confirmation given the limited literature on venlafaxine use during pregnancy and risk for birth defects. Our results suggest confounding by underlying conditions should be considered when assessing risk. Fully informed treatment decision-making requires balancing the risks and benefits of proposed interventions against those of untreated depression or anxiety.

Congenital diaphragmatic hernia and maternal dietary nutrient pathways and diet quality.

We examined the association of congenital diaphragmatic hernia (CDH) with maternal dietary intake, using semi-Bayes hierarchical models and principal components analysis to consider intake of nutrients that contribute to one-carbon metabolism and oxidative stress pathways, and a diet quality index. We included data on 825 cases and 11,108 nonmalformed controls born from 1997-2011 whose mother participated in the National Birth Defects Prevention Study (NBDPS), a multisite, population-based case-control study. Exposure data were from maternal telephone interviews, which included a food frequency questionnaire. Adjusted odds ratios (aOR) and 95% confidence intervals (CI) were generated from logistic regression models that included nutritional factors as continuous variables and were adjusted for maternal energy intake, race-ethnicity, parity, and vitamin supplement intake. In the semi-Bayes hierarchical model that included all nutrients and confounders, riboflavin was the only nutrient for which the 95% CI excluded 1.0; the aOR for a 1 SD increase was 0.83. The aORs were 0.79 (95% CI 0.69-0.91) for the one-carbon metabolism pathway score, 0.90 (95% CI 0.80-1.01) for oxidative stress, and 0.85 (95% CI 0.77-0.93) for diet quality (the aORs correspond to a 1 SD increase). The findings from this study provide some support for the hypothesis that better prepregnancy nutrition is associated with reduced risk for CDH. These results provide etiologic clues but should be interpreted with caution given the novelty of the investigation.

Asthma Medication Use and Risk of Birth Defects: National Birth Defects Prevention Study, 1997-2011

Evidence regarding associations between maternal asthma medication use and birth defects is mixed. Estimate associations between asthma medciation use and 52 birth defects using National Birth Defects Prevention Study data from 1997 to 2011. We compared self-reported maternal asthma medication use for 28,481 birth defect cases and 10,894 nonmalformed controls. We calculated adjusted odds ratios (95% CIs) to estimate the risk of birth defects associated with early pregnancy asthma medication use (the month before through the third month of pregnancy), controlling for maternal age, race/ethnicity, body mass index, smoking, folic acid-containing supplement use, and parity. We calculated risks by medication groupings: bronchodilators, anti-inflammatories, and both. Overall, 1304 (5%) case and 449 (4%) control women reported early pregnancy asthma medication use. We observed an association between asthma medication use and longitudinal limb deficiency (1.81; 95% CI, 1.27-2.58). Early pregnancy bronchodilator-only use was associated with cleft palate (1.50; 95% CI, 1.11-2.02), cleft lip (1.58; 95% CI, 1.12-2.23), longitudinal limb deficiency (2.35; 95% CI, 1.55-3.54), and truncus arteriosus (2.48; 95% CI, 1.13-5.42). Although early pregnancy anti-inflammatory-only use was not associated with the birth defects studied, use of both medications was associated with biliary atresia (3.60; 95% CI, 1.55-8.35) and pulmonary atresia (2.50; 95% CI, 1.09-5.78). Consistent with previous National Birth Defects Prevention Study analyses, asthma medication use was not associated with most birth defects examined, but we observed modest risks for bronchodilator use and several birth defects. Our findings support maintaining adequate asthma treatment during pregnancy, because early pregnancy asthma exacerbations have been associated with adverse birth outcomes, including birth defects.

Maternal Hypertension-Related Genotypes and Congenital Heart Defects.

Maternal hypertension has been associated with congenital heart defect occurrence in several studies. We assessed whether maternal genotypes associated with this condition were also associated with congenital heart defect occurrence. We used data from the National Birth Defects Prevention Study to identify non-Hispanic white (NHW) and Hispanic women with (cases) and without (controls) a pregnancy in which a select simple, isolated heart defect was present between 1999 and 2011. We genotyped 29 hypertension-related single nucleotide polymorphisms (SNPs). We conducted logistic regression analyses separately by race/ethnicity to assess the relationship between the presence of any congenital heart defect and each SNP and an overall blood pressure genetic risk score (GRS). All analyses were then repeated to assess 4 separate congenital heart defect subtypes. Four hypertension-related variants were associated with congenital heart defects among NHW women (N = 1,568 with affected pregnancies). For example, 1 intronic variant in ARHGAP2, rs633185, was associated with conotruncal defects (odds ratio [OR]: 1.3, 95% confidence interval [CI]: 1.1-1.6). Additionally, 2 variants were associated with congenital heart defects among Hispanic women (N = 489 with affected pregnancies). The GRS had a significant association with septal defects (OR: 2.1, 95% CI: 1.2-3.5) among NHW women. We replicated a previously reported association between rs633185 and conotruncal defects. Although additional hypertension-related SNPs were also associated with congenital heart defects, more work is needed to better understand the relationship between genetic risk for maternal hypertension and congenital heart defects occurrence.

Abstract PR03: Sex ratio disparities and the risk of childhood cancer: Evaluating the mediating effect of birth defects among 15,000 childhood cancer cases

Abstract Background: There is a persistent yet unexplained disparity in the sex ratio among childhood cancer cases, whereby males are more likely to develop several cancers. These patterns are also seen for most birth defects, which are strongly associated with the risk of childhood cancer. We conducted a mediation analysis to estimate whether birth defect status mediates the association between sex and childhood cancer risk. Methods: We linked data from birth, birth defects, and cancer registries to obtain a population-based birth cohort including births from 1992-2013 in Arkansas, Michigan, North Carolina, and Texas. We obtained birth defects diagnoses, including chromosomal and nonchromosomal defects, from statewide, population-based birth defects registries. We focused on “major” defects as defined by the National Birth Defects Prevention Network and the National Birth Defects Prevention Study. Cancer diagnoses that occurred prior to age 18 years were obtained from state cancer registries. We obtained data on child’s sex, birth weight, gestational age, maternal race/ethnicity, maternal age, and plurality from birth records. We conducted counterfactual mediation analysis to estimate the direct and indirect effects of sex on risk of childhood cancer, modeling sex as the exposure, birth defect status as the mediator, and cancer type as the outcome. State, maternal race/ethnicity (white, black, other), maternal age (continuous), and plurality (singleton vs. multiple) were considered potential mediator-outcome confounders. Due to lower success rates of linkage to birth records among adolescent cancer cases, we conducted a sensitivity analysis limiting to cancers diagnosed at age &amp;lt; 5 years. Results: Our dataset included 10,181,074 children (5,208,379 males; 4,972,695 females), including 15,110 with cancer diagnoses (8044 males; 7066 females), 539,567 children with birth defects diagnoses (320,666 males; 218,901 females), and 2,124 co-occurring cases (children with both cancer and one or more birth defect diagnosis: 1,186 males; 938 females). We observed mediation of the association between sex and childhood cancer overall by birth defect status (proportion mediated [PM]: 38%). In analyses of specific cancer types, we observed variation of the estimated proportion mediated among several cancers, including hepatoblastoma (PM: 33%), neuroblastoma (PM: 35%), non-Hodgkin lymphoma (PM: 6%), and soft tissue sarcomas (PM: 25%). In analysis of children age &amp;lt; 5 years at cancer diagnosis, we observed similar results. Conclusions: Our results suggest that birth defects mediate a significant proportion of the overall relationship between sex and childhood cancer. While approximately 60% of the male excess in childhood cancer cases remains unexplained, these findings add to our understanding of the causal pathway of male sex as a risk factor for childhood cancer. Additional studies are under way to characterize the biology underlying these observations. This abstract is also being presented as Poster A66. Citation Format: Erin L. Marcotte, Jeremy M. Schraw, Tania A. Desrosiers, Wendy N. Nembhard, Peter H. Langlois, Mark A. Canfield, Robert E. Meyer, Sharon E. Plon, Philip Lupo. Sex ratio disparities and the risk of childhood cancer: Evaluating the mediating effect of birth defects among 15,000 childhood cancer cases [abstract]. In: Proceedings of the AACR Special Conference on the Advances in Pediatric Cancer Research; 2019 Sep 17-20; Montreal, QC, Canada. Philadelphia (PA): AACR; Cancer Res 2020;80(14 Suppl):Abstract nr PR03.

Use of antihistamine medications during early pregnancy and selected birth defects: The National Birth Defects Prevention Study, 1997-2011.

It is estimated that approximately 10-15% of pregnant women report antihistamine use during pregnancy. Although antihistamines are generally considered safe during pregnancy, results from published studies are inconsistent. Using a case-control study design we analyzed 41,148 pregnancies (30,091 cases and 11,057 controls) from the National Birth Defects Prevention Study (1997-2011). Logistic regression models were used to estimate odds ratios (OR) and 95% confidence intervals for 64 birth defect groupings in relation to early pregnancy exposure to 14 distinct antihistamines. Models were adjusted for maternal age, race, parity, education level, prenatal care, folic acid use, smoking and alcohol use, and study site. Approximately 13% of cases and controls were exposed to an antihistamine during early pregnancy. Analyses were restricted to those defects where more than five cases were exposed to the antihistamine of interest, generating 340 analyses which yielded 20 (5.9%) significant positive associations (adjusted ORs ranging from 1.21 to 4.34). Only a few of our findings were consistent with previous studies. There is a lack of strong evidence to conclude that birth defects are associated with exposure to antihistamines during early pregnancy.

Trends in first-trimester nausea and vomiting of pregnancy and use of select treatments: Findings from the National Birth Defects Prevention Study.

Although nausea and vomiting of pregnancy (NVP) is common, the secular and demographic trends of NVP and its treatments are not well-studied. To describe the prevalence and patterns of first-trimester NVP and selected treatments among controls in the National Birth Defects Prevention Study (NBDPS). National Birth Defects Prevention Study is a population-based case-control study of birth defects in the United States (1997-2011). We collected self-reported data about NVP and use of commonly reported pharmacological and herbal/natural treatments (ondansetron, promethazine, pyridoxine, metoclopramide, doxylamine succinate, ginger, phosphorated carbohydrate solution, and prochlorperazine) from mothers of non-malformed control infants. We estimated the prevalence of NVP and selected treatments and examined secular and demographic trends (education, race/ethnicity, and maternal age) for such use, adjusting for study centre. Among 10540 mothers of controls, 7393 women (70.1%) reported first-trimester NVP, and 12.2% of those used one or more of the commonly reported treatments. Specific treatment use varied after adjustment for study centre (ondansetron: 3.4%; promethazine: 4.2%; pyridoxine: 3.2%; metoclopramide: 0.7%; doxylamine succinate: 1.7%; ginger: 1.0%; phosphorated carbohydrate solution: 0.4%; and prochlorperazine: 0.3%). Treatment use increased for each agent over the study period. Women with more years of education reported more NVP and treatment use. White (72%), Hispanic (71%), and other race (73%) women reported more NVP than Black women (67%); White women used selected NVP treatments most frequently, and Black women used them more than Hispanic women. Though women aged 25-34years reported more NVP (72%) than younger (69%) or older (67%) women, the frequency of medication use was similar among women aged 25-34 and ≥35, and lower among women aged <25years. National Birth Defects Prevention Study controls reported NVP at frequencies similar to those previously reported. Of note, we observed an increase in use of selected treatments over time, and variations in NVP and treatments by study site and demographic factors.

Specific Birth Defects in Pregnancies of Women With Diabetes: National Birth Defects Prevention Study, 1997–2011

(Abstracted from Am J Obstet Gynecol 2020;222:176.e1–176.e11) The National Birth Defects Prevention Study (NBDPS) was one of the first analyses to report the association between diabetes and birth defects. The study’s data of approximately 18,000 deliveries from October 1997 to December 2003 showed strong associations with many birth defects, primarily with pregestational diabetes but also with gestational diabetes.

Vasoactive exposures and risk of amniotic band syndrome and terminal transverse limb deficiencies.

Amniotic band syndrome (ABS) includes limb deficiencies accompanied by fibrous strands originating from the amniotic lining. Terminal transverse limb deficiencies (TTLD) appear to be similar but lack fibrous strands. Both are hypothesized to result from vascular disruption. For ABS, limb deficiencies are considered secondary to amnion rupture. We explored an alternative possibility-that TTLD is the primary defect and ABS is secondary. Using data from the National Birth Defects Prevention Study, we expanded on a previous study. We examined smoking, alcohol, and medications categorized by indicated vasoactivity as markers of vascular disruption. Logistic regression models with Firth's penalized likelihood were used to estimate adjusted odds ratios (aORs) and 95% confidence intervals (CIs). Use of bronchodilators and aspirin appeared to increase the risk of ABS, while decongestants and nonaspirin NSAIDs increased the risk of TTLD. The risk of ABS was markedly increased in cases reporting combinations of vasoactive exposures, particularly alcohol and aspirin (aOR 3.7, 95% CI 1.6, 7.8), and alcohol and bronchodilators (aOR 3.4, 95% CI 1.4, 7.5). Increased risk of TTLD due to combinations of vasoactive exposures was only observed for smoking and decongestants (aOR 2.3, 95% CI 1.4, 3.6). Exposures associated with increased risk of ABS had no apparent association with TTLD, supporting previous evidence that these may be distinct phenotypes. ABS appears to be associated with combined exposures with vasodilation properties, such as alcohol and bronchodilators, while increased risk of TTLD may be associated with smoking and decongestants, both vasoconstrictive exposures.

Maternal occupational exposure to polycyclic aromatic hydrocarbons and the risk of isolated congenital heart defects among offspring

BackgroundAlthough there is evidence in experimental model systems that exposure to polycyclic aromatic hydrocarbons (PAHs) is linked with congenital heart defects (CHDs), few studies have examined the association in humans. We conducted a case-control study to examine the association between maternal exposure to PAHs and CHDs in offspring using data from the National Birth Defects Prevention Study (NBDPS) (1997–2011). MethodsWe obtained detailed information on maternal occupation during the month before to three months after conception. Expert raters, masked to case-control status, assessed job descriptions to assign categorical levels of exposure. Categories were quantitatively mapped to estimate cumulative exposure to PAHs, incorporating exposure intensity, frequency, work duration, and work hours. Quartiles were generated for cumulative maternal exposure to PAHs. Crude and adjusted odds ratios (ORs) with 95% confidence intervals (CIs) were estimated using unconditional logistic regression for quartiles of PAH exposure and six CHD groupings (e.g. conotruncal) and specific subtypes (e.g. tetralogy of Fallot [ToF]). Final models were adjusted for maternal age, race/ethnicity, education, smoking, anticonvulsant use, folic acid supplementation, and study center. ResultsThere were 4,775 case and 7,734 control infants eligible for the study. The prevalence of occupational exposure to PAHs was 10.2% among both case and control mothers. In adjusted analysis, compared to mothers with no occupational PAH exposure, those in the highest quartile of exposure were more likely to have offspring in the conotruncal heart defects group (OR 1.41; 95% CI 1.00–2.00), and with ToF (OR 1.83; 95% CI 1.21–2.78). ConclusionsWomen in the highest quartile of estimated cumulative occupational PAH exposure during early pregnancy were more likely to have offspring with conotruncal heart defects, specifically ToF, compared to women with no occupational PAH exposure. Other comparisons between PAHs and other CHDs subgroups did not show any statistically precise associations.