Guidelines for case classification for the National Birth Defects Prevention Study

Parental occupational pesticide exposure and nonsyndromic orofacial clefts

Nonsyndromic orofacial clefts are common birth defects. Reported risks for orofacial clefts associated with parental occupational pesticide exposure are mixed. To examine the role of parental pesticide exposure in orofacial cleft development in offspring, this study compared population-based case-control data for parental occupational exposures to insecticides, herbicides, and fungicides, alone or in combinations, during maternal (1 month before through 3 months after conception) and paternal (3 months before through 3 months after conception) critical exposure periods between orofacial cleft cases and unaffected controls. Multivariable logistic regression was used to estimate odds ratios, adjusted for relevant covariables, and 95% confidence intervals for any (yes, no) and cumulative (none, low [<median exposure level in controls], high [≥median exposure level in controls]) occupational pesticide exposures and cleft lip ± cleft palate and cleft palate. Associations for cleft lip ± cleft palate tended to be near unity for maternal or paternal occupational pesticide exposures, except for low paternal exposure to any pesticide, which produced a statistically significant inverse association with this subtype. Associations for cleft palate tended to be near unity for maternal exposures and mostly positive, but non-significant, for paternal exposures; a significant positive association was observed between paternal low exposure to insecticide + herbicide + fungicide and cleft palate. Combined parental exposure produced non-significant associations near or below unity for all orofacial cleft cases combined and cleft lip ± cleft palate and positive, but non-significant, associations for cleft palate. This study observed associations mostly near unity between maternal occupational pesticide exposure and orofacial clefts. Associations for paternal occupational pesticide exposures were mostly near or below unity for cleft lip ± cleft palate, and mostly positive for cleft palate. However, due to the limitations of this study, these subtype-specific results should be interpreted cautiously. Future research examining parental occupational pesticide exposure and orofacial clefts should attempt to improve exposure assessment and increase sample size to better facilitate risk estimation.

Maternal ambient heat exposure during early pregnancy in summer and spring and congenital heart defects - A large US population-based, case-control study

BACKGROUND/OBJECTIVE

Few studies have assessed the effect of ambient heat during the fetal development period on congenital heart defects (CHDs), especially in transitional seasons. We examined and compared the associations between extreme heat and CHD phenotypes in summer and spring, assessed their geographical differences, and compared different heat indicators.

METHODS

We identified 5848 CHD cases and 5742 controls (without major structural defects) from the National Birth Defects Prevention Study, a US multicenter, population-based case-control study. Extreme heat events (EHEs) were defined by using the 95th (EHE95) or 90th (EHE90) percentile of daily maximum temperature and its frequency and duration during postconceptional weeks 3-8. We used a two-stage Bayesian hierarchical model to examine both regional and study-wide associations. Exposure odds ratios (ORs) were calculated using multivariate logistic regression analyses, while controlling for potential confounding factors.

RESULTS

Overall, we observed no significant relationships between maternal EHE exposure and CHDs in most regions during summer. However, we found that 3-11 days of EHE90 during summer and spring was significantly associated with ventricular septal defects (VSDs) study-wide (ORs ranged: 2.17-3.24). EHE95 in spring was significantly associated with conotruncal defects and VSDs in the South (ORs: 1.23-1.78). Most EHE indicators in spring were significantly associated with increased septal defects (both VSDs and atrial septal defects (ASDs)) in the Northeast.

CONCLUSION

While generally null results were found, long duration of unseasonable heat was associated with the increased risks for VSDs and ASDs, mainly in South and Northeast of the US. Further research to confirm our findings is needed.

Epidemiology of anophthalmia and microphthalmia: Prevalence and patterns in Texas, 1999-2009

Anophthalmia and microphthalmia are a set of rare, yet severe, birth defects considered to be part of a spectrum of developmental ocular malformations ranging from smaller than average to completely absent eyes. Despite their clinical significance, little is known about the etiologies of these conditions. The goal of this study was to expand our understanding of the epidemiology of anophthalmia and microphthalmia. Data for this population-based assessment were obtained from the Texas Birth Defects Registry (TBDR) and Center for Health Statistics for the period 1999-2009. Descriptive analyses and estimates of birth prevalence and prevalence ratios (PR) were determined for this defect. There were 1,262 definite anophthalmia and microphthalmia patients identified in the TBDR, with an overall combined prevalence of 3.0 per 10,000 live births. More than half (55.7%) of the patients had at least one chromosome abnormality or syndrome. In addition, 92.4% of nonsyndromic patients (i.e., have no recorded chromosome abnormalities or syndromes) had at least one additional birth defect. After adjustment for multiple factors, the prevalence of nonsyndromic anophthalmia and microphthalmia was higher among mothers who had ≥2 previous fetal deaths (PR = 1.43, 95% confidence interval [CI]: 1.03-1.97) and among mothers with any reported diabetes (PR = 2.08, 95% CI: 1.49-2.90). Our results confirm that children with anophthalmia and microphthalmia frequently have genetic syndromes or are born with other major birth defects. Our findings add to the limited body of literature on anophthalmia and microphthalmia as well as help define subgroups of women who are more likely to have children with this malformation.

Comprehensive investigation of congenital anomalies in cerebral palsy: protocol for a European-Australian population-based data linkage study (The Comprehensive CA-CP Study)

INTRODUCTION

Cerebral palsy (CP), an umbrella term for non-progressive conditions of cerebral origin resulting in motor impairments, is collectively the most common cause of physical disability in childhood. Cerebral and/or non-cerebral congenital anomalies are present in 15%-40% of children with CP. In order to identify effective prevention strategies for this substantial proportion of CP, a comprehensive understanding of the epidemiology of these congenital anomalies is required. International collaboration is needed, as previous attempts have fallen short due to a lack of power, since the anomalies are individually rare and CP comprises many clinical descriptions. The aim of this study is to generate new knowledge about the aetiologies of CP through a focused investigation into the role of congenital anomalies.

METHODS AND ANALYSIS

This collaborative, population-based data linkage study includes nine geographic regions (six in Europe, three in Australia) served by both congenital anomaly and CP registers. Register data for children with CP (both with and without congenital anomalies) and children with specific congenital anomalies (without CP) born between 1991 and 2009 will be linked and de-identified within each region. The resulting linked data sets will be quality assured, recoded, harmonised and then pooled into one data set. Analysis of the combined data set will include: frequencies/proportions of congenital anomalies and outcomes (type of CP, severity, impairments); descriptive analyses comparing timing of congenital anomaly development and brain injury/abnormality responsible for CP; ORs to calculate the odds of CP following a specific congenital anomaly; and identification of anomalies on causal pathways to CP.

ETHICS AND DISSEMINATION

Ethics approval for this collaborative study, The Comprehensive CA-CP Study, has been obtained from the Cerebral Palsy Alliance Human Research Ethics Committee (EC00402). Study findings will be disseminated at conferences and published in peer-reviewed journals, and recommendations will be made regarding the collection and classification of congenital anomaly data by CP registers.

Risk of major congenital malformations following first-trimester exposure to vaginal azoles used for treating vulvovaginal candidiasis: a population-based retrospective cohort study

OBJECTIVE

To evaluate the risk for major malformations following first-trimester exposure to vaginal azoles.

DESIGN

A population-based retrospective cohort study of women exposed to vaginal azoles from the first day of the last menstrual period until the 90th gestational day.

SETTING

A combination of four computerised databases: medications, birth, infant hospitalizations, and pregnancy terminations.

POPULATION

All women who gave birth or underwent a pregnancy termination at Soroka Medical Center, Beer-Sheva, Israel, between 1999 and 2009.

METHODS

Crude and adjusted relative risks for major congenital malformations and for specific malformations according to organ systems were calculated using a multivariate negative binomial regression. Potential confounders were assessed and controlled for included parity, maternal age, ethnicity, maternal diabetes, smoking, and year of birth or pregnancy termination. Additional analysis using propensity score matching was performed for selected malformations.

MAIN OUTCOME MEASURES

Major malformations as well as specific malformations according to organ systems.

RESULTS

Of 101 615 pregnancies, 1993 (1.96%) were exposed to clotrimazole vaginal tablets and 313 (0.31%) to miconazole vaginal tablets during the first trimester of pregnancy. No association was found between first-trimester exposure to clotrimazole and major or specific malformations. An association was found between miconazole exposure and musculoskeletal malformation in general and other congenital musculoskeletal anomalies in particular. However, no association was detected when propensity score matching was used.

CONCLUSIONS

Intrauterine exposure to vaginal azoles during the first trimester of pregnancy was not associated with either major or specific malformations according to organ systems.

TWEETABLE ABSTRACT

First-trimester exposure to vaginal azoles is not associated with either major or specific malformations.

Multiple bias analysis using logistic regression: an example from the National Birth Defects Prevention Study

PURPOSE

Exposure misclassification, selection bias, and confounding are important biases in epidemiologic studies, yet only confounding is routinely addressed quantitatively. We describe how to combine two previously described methods and adjust for multiple biases using logistic regression.

METHODS

Weights were created from selection probabilities and predictive values for exposure classification and applied to multivariable logistic regression models in a case-control study of prepregnancy obesity (body mass index ≥30 vs. <30 kg/m²) and cleft lip with or without cleft palate (CL/P) using data from the National Birth Defects Prevention Study (2523 cases, 10,605 controls).

RESULTS

Adjusting for confounding by race/ethnicity, prepregnancy obesity, and CL/P were weakly associated (odds ratio [OR]: 1.10; 95% confidence interval: 0.98, 1.23). After weighting the data to account for exposure misclassification, missing exposure data, selection bias, and confounding, multiple bias-adjusted ORs ranged from 0.94 to 1.03 in nonprobabilistic bias analyses and median multiple bias-adjusted ORs ranged from 0.93 to 1.02 in probabilistic analyses.

CONCLUSIONS

This approach, adjusting for multiple biases using a logistic regression model, suggested that the observed association between obesity and CL/P could be due to the presence of bias.

Nongenetic risk factors for holoprosencephaly: An updated review of the epidemiologic literature

Holoprosencephaly (HPE) is a major structural birth defect of the brain that occurs in approximately 1 in 10,000 live births. Although some genetic causes of HPE are known, a substantial proportion of cases have an unknown etiology. Due to the low birth prevalence and rarity of exposure to many potential risk factors for HPE, few epidemiologic studies have had sufficient sample size to examine risk factors. A 2010 review of the literature identified several risk factors that had been consistently identified as occurring more frequently among cases of HPE, including maternal diabetes, twinning, and a predominance of females, while also identifying a number of potential risk factors that had been less widely studied. In this article, we summarize a systematic literature review conducted to update the evidence for nongenetic risk factors for HPE.

Maternal underweight and obesity and risk of orofacial clefts in a large international consortium of population-based studies

Background

Evidence on association of maternal pre-pregnancy weight with risk of orofacial clefts is inconsistent.

Methods

Six large case-control studies of orofacial clefts from Northern Europe and the USA were included in analyses pooling individual-level data. Cases included 4943 mothers of children with orofacial clefts (cleft lip only: 1135, cleft palate with cleft lip: 2081, cleft palate only: 1727) and controls included 10 592 mothers of unaffected children. Association of orofacial cleft risk with pre-pregnancy maternal weight classified by level of body mass index (BMI, kg/m 2 ) was evaluated using logistic regression adjusting for multiple covariates.

Results

Cleft palate, both alone and with cleft lip (CP+/-CL), was associated with maternal class II+ pre-pregnancy obesity (≥ 35)compared with normal weight [adjusted odds ratio (aOR) = 1.36; 95% confidence interval (CI) = 1.16, 1.58]. CP+/-CL was marginally associated with maternal underweight (aOR = 1.16; 95% CI = 0.98, 1.36). Cleft lip alone was not associated with BMI.

Conclusions

In this largest population-based study to date, we found an increased risk of cleft palate, with or without cleft lip, in class II+ obese mothers compared with normal-weight mothers; underweight mothers may also have an increased risk, but this requires further study. These results also suggest that extremes of weight may have a specific effect on palatal development.

Pregnancy and neonatal outcomes following letrozole use in frozen-thawed single embryo transfer cycles

STUDY QUESTION

Are pregnancy and neonatal outcomes following letrozole use comparable with natural and HRT cycles in patients undergoing single frozen-thawed embryo transfer (FET)?

SUMMARY ANSWER

Letrozole use was significantly associated with higher rates of clinical pregnancy, clinical pregnancy with fetal heart beat and live birth, and with a lower rate of miscarriage, compared with natural and HRT cycles.

WHAT IS KNOWN ALREADY

Letrozole is the most commonly used aromatase inhibitor for mild ovarian stimulation in ART. However, the effect of letrozole on pregnancy and neonatal outcomes in FET are not well known.

STUDY DESIGN SIZE, DURATION

A retrospective cohort study was conducted using data from the Japanese national ART registry between 2012 and 2013.

PARTICIPANTS/MATERIALS SETTING METHODS

A total of 110 722 single FET cycles with letrozole (n = 2409), natural (n = 41 470) or HRT cycles (n = 66 843) were included. The main outcomes were the rates of clinical pregnancy, clinical pregnancy with fetal heart beat, miscarriage and live birth. Adjusted odds ratios and relative risks (RRs) were calculated using a generalized estimating equation adjusting for correlations within clinics.

MAIN RESULTS AND THE ROLE OF CHANCE

The rates of clinical pregnancy, clinical pregnancy with fetal heart beat, and live birth were significantly higher, while the rate of miscarriage was significantly lower in the letrozole group compared with the natural and HRT groups. In blastocyst stage transfers, the adjusted RRs for clinical pregnancy with fetal heart beat of letrozole compared with natural and HRT cycles were 1.48 (95% CI: 1.41-1.55) and 1.62 (95% CI: 1.54-1.70), respectively. Similarly, the adjusted RRs of letrozole for miscarriage compared with natural and HRT cycles were 0.91 (95% CI: 0.88-0.93) and 0.84 (95% CI: 0.82-0.87), respectively. Neonatal outcomes were mostly similar in letrozole, natural and HRT cycles.

LIMITATIONS REASONS FOR CAUTION

Important limitations of this study included the lack of information concerning the reasons for selecting the specific FET method, parity, the number of previous ART failures, embryo quality and the dose and duration of letrozole intake.

WIDER IMPLICATIONS OF THE FINDINGS

These results suggest that letrozole use may improve clinical pregnancy, clinical pregnancy with fetal heart beat, and live births and reduce the risk of miscarriage in patients undergoing single FET cycles.

STUDY FUNDING/COMPETING INTEREST(S)

No external funding was used for this study. There are no conflicts of interest.

TRIAL REGISTRATION NUMBER

Not applicable.

Nutrient intake in women before conception and risks of anophthalmia and microphthalmia in their offspring

BACKGROUND

We previously explored associations between nutrients including folate and other macro and micronutrients and risks of anophthalmia or microphthalmia in the National Birth Defects Prevention Study. In the current study, we expand those previous results with larger sample sizes and conduct analyses with an additional diet quality index using more recent data.

METHODS

The National Birth Defects Prevention Study is a population-based, multicenter case-control study of over 30 major birth defects, with estimated due dates from October 1997 to December 2011. Cases were 224 infants diagnosed with anophthalmia or microphthalmia. Controls were 11,109 live-born, nonmalformed infants randomly selected by each study center. Mothers completed a standardized, computer-assisted telephone interview between 6 weeks and 24 months after delivery. Mothers responded to a shortened food frequency questionnaire, assessing their nutrient intake for the year before pregnancy, and questions about periconceptional (2 months before to 2 months after conception) vitamin supplement use. Nutrient intake quartiles were based on the intake among controls.

RESULTS

Among vitamin supplement users, odds of anophthalmia/microphthalmia were decreased for women with intake levels in the highest quartile of folate (0.56, 95% confidence interval [CI] 0.32-0.98), magnesium (0.42, 95% CI 0.22-0.82), and vitamin E (0.50, 95% CI 0.29-0.89). Among women not reporting vitamin supplement use, the odds were significantly increased for beta-carotene (2.5, 95% CI 1.10-5.68) and decreased for retinol (0.37, 95% CI 0.19-0.73).

CONCLUSIONS

In this expanded analysis, we observed associations for a few nutrients, specifically forms of vitamin A. However, the heterogeneity of results by form and vitamin use necessitates further inquiry.

Low carbohydrate diets may increase risk of neural tube defects

BACKGROUND

Folic acid fortification significantly reduced the prevalence of neural tube defects (NTDs) in the United States. The popularity of "low carb" diets raises concern that women who intentionally avoid carbohydrates, thereby consuming fewer fortified foods, may not have adequate dietary intake of folic acid.

METHODS

To assess the association between carbohydrate intake and NTDs, we analyzed data from the National Birth Defects Prevention Study from 1,740 mothers of infants, stillbirths, and terminations with anencephaly or spina bifida (cases), and 9,545 mothers of live born infants without a birth defect (controls) conceived between 1998 and 2011. Carbohydrate and folic acid intake before conception were estimated from food frequency questionnaire responses. Restricted carbohydrate intake was defined as ≤5th percentile among controls. Odds ratios were estimated with logistic regression and adjusted for maternal race/ethnicity, education, alcohol use, folic acid supplement use, study center, and caloric intake.

RESULTS

Mean dietary intake of folic acid among women with restricted carbohydrate intake was less than half that of other women (p < .01), and women with restricted carbohydrate intake were slightly more likely to have an infant with an NTD (AOR = 1.30, 95% CI: 1.02, 1.67).

CONCLUSIONS

This is the first study to examine the association between carbohydrate intake and NTDs among pregnancies conceived postfortification. We found that women with restricted carbohydrate intake were 30% more likely to have an infant with anencephaly or spina bifida. However, more research is needed to understand the pathways by which restricted carbohydrate intake might increase the risk of NTDs.

Maternal occupational cadmium exposure and nonsyndromic orofacial clefts

BACKGROUND

Cigarette smoking is a well-studied risk factor for orofacial clefts (OFCs). Little is known about which constituents in cigarette smoke contribute to this teratogenicity in humans. One constituent, cadmium, has been associated with OFCs in animal studies; in humans, the role of maternal cadmium exposure on OFCs, independent of cigarette smoke, is unclear. In particular, the relation between maternal occupational cadmium exposure and OFCs is largely unexplored.

METHODS

Using data from a large, population-based case-control study, we compared expert rater assessed maternal occupational cadmium exposure from self-reported occupational histories during the period 1 month before through 3 months after conception between OFC cases (n = 1,185) and unaffected controls (n = 2,832). Multivariable logistic regression analyses were used to estimate adjusted odds ratios (aORs) and 95% confidence intervals for any (yes/no) and cumulative (no, low, high exposure) occupational cadmium exposures and all OFCs, cleft lip ± cleft palate (CL/P) and cleft palate (CP).

RESULTS

Overall, 45 mothers (cases = 13, controls = 32) were rated as having occupational cadmium exposure. Comparing all OFCs to controls, we observed inverse, nonsignificant aORs for any or low exposure, and positive, nonsignificant aORs for high exposure. Where data were available, aORs for CL/P and CP tended to parallel those for all OFCs.

CONCLUSION

To our knowledge, this is the first study to specifically examine maternal occupational cadmium exposure and OFCs, using expert rater exposure assessment. The small numbers of exposed mothers observed, however, led to imprecise estimates. Continued research using more detailed occupational exposure assessment and increased sample sizes is recommended.

Pregnancy outcomes in women on metformin for diabetes or other indications among those seeking teratology information services

AIMS

Metformin is used to treat type 2 diabetes, polycystic ovary syndrome associated infertility, and gestational diabetes. This study aims to evaluate the safety of metformin in early pregnancy.

METHOD

We evaluated the risk of major birth defects and pregnancy losses in a cohort of pregnant women exposed to metformin during the first trimester for different indications relative to a matched unexposed reference group.

RESULTS

The risk of major birth defects was 5.1% (20/392) in pregnancies exposed to metformin during the first trimester and 2.1% (9/431) in the reference group [adjusted odds ratio (OR) 1.70; 95% CI 0.70-4.38]. Among metformin users, this risk was 7.8% (17/219) in patients with pre-gestational diabetes and 1.7% (3/173) in those without this diagnosis. Compared to the unexposed reference, the OR for metformin user with diabetes was 3.95 (95% CI 1.77-9.41) and for metformin with other indications it was 0.83 (95% CI 0.18-2.81). The risk of pregnancy losses (spontaneous abortions and stillbirths) was 20.8% in women on metformin during the first trimester and 10.8% in the reference group [adjusted hazard ratio (HR) 1.57; 95% CI 0.90-2.74]. The risks for women on metformin with and without pre-gestational diabetes were 24.0% and 16.8% respectively, with adjusted HR of 2.51 (95% CI 1.44-4.36) and 1.38 (95% CI 0.74-2.59) when compared to the reference.

CONCLUSION

Pregnant women with pre-gestational diabetes on metformin are at a higher risk for adverse pregnancy outcomes than the general population. This appears to be due to the underlying diabetes since women on metformin for other indications do not present meaningfully increased risks.

Antioxidant Consumption is Associated with Decreased Odds of Congenital Limb Deficiencies

BACKGROUND

Approximately 1 in 2000 infants is born with a limb deficiency in the US. Research has shown that women's periconceptional diet and use of vitamin supplements can affect risk of birth defects. We investigated whether maternal consumption of nutritional antioxidants was associated with occurrence of transverse limb deficiency (TLD) and longitudinal limb deficiencies (LLD).

METHODS

We analysed case-control data from mothers and their singleton infants with TLD (n = 566), LLD (n = 339), or no malformation (controls; n = 9384) in the National Birth Defects Prevention Study (1997-2009). Using a modified food frequency, we estimated usual pre-pregnancy antioxidant consumption by total fruit and vegetable consumption (in grams) grouped into tertiles, and cumulative antioxidant score (ranging from 1 to 10) based on consumption of three antioxidants: beta-carotene, lycopene, and lutein. We estimated odds ratios (OR) adjusted for maternal age, race/ethnicity, education, smoking, alcohol use, body mass index, and total energy.

RESULTS

Compared to women in the lowest tertile of fruit and vegetable consumption, women in the highest tertile were less likely to have infants with TLD (OR 0.74, 95% CI 0.57, 0.96) or LLD (OR 0.82, 95% CI 0.59, 1.13). Compared to the lowest antioxidant consumption score of 1, those with the highest score of 10 had ORs of 0.68 (95% CI 0.48, 0.95) for TLD and 0.77 (95% CI 0.50, 1.17) for LLD.

CONCLUSIONS

Dietary intake of antioxidants was associated with reduced odds of limb deficiencies. These findings add further evidence for women's periconceptional diet reducing occurrence of some birth defects.

The Risk of Adverse Pregnancy Outcome After First Trimester Exposure to H1 Antihistamines: A Systematic Review and Meta-Analysis

INTRODUCTION

H1 antihistamines are used for the treatment of nausea and vomiting during pregnancy as well as the symptomatic relief of asthma, urticaria, allergy, and the common cold. Although they are overall felt to be safe during pregnancy, recently several studies have challenged this assumption, as millions of women are exposed to them in the first trimester.

METHODS

Following the guidelines of PRISMA, a systematic review was performed to retrieve all published articles involving H1-antihistamine exposure during pregnancy. Electronic databases including PubMed and EMBASE were searched for possibly relevant articles published in any language up to December 2015.

RESULTS

After removing duplicate publications, and excluding animal studies and studies on drug effectiveness, 342 articles were reviewed in detail and 37 studies fulfilled the inclusion criteria for the meta-analysis. In cohort studies, the risk of major malformation in the offspring of women exposed to H1 antihistamines was not higher than that of the control population (OR 1.07; 95% CI 0.98-1.16). The Q-statistic for heterogeneity of effects was not significant (p > 0.05, I ² < 25%) and there was no evidence of publication bias. Similar results were achieved with case-control studies (OR 1.05; 95% CI 0.90-1.23). Similarly, H1 antihistamines were not associated with more spontaneous abortions (OR 1.00; 95% CI 0.83-1.20), prematurity (OR 0.96; 95% CI 0.76-1.20), stillbirth (OR 1.23; 95% CI 0.48-3.18) or low birth weight (OR 1.20; 95% CI 0.63-2.29).

CONCLUSIONS

Based on our meta-analyses, which included a large number of studies, H1 antihistamines are not associated with an increased risk of major malformation or other adverse fetal outcomes. This study provides important information to both pregnant women and their healthcare providers regarding the safety and risk of H1 antihistamine use during this sensitive time.

Maternal report of fever from cold or flu during early pregnancy and the risk for noncardiac birth defects, National Birth Defects Prevention Study, 1997-2011

BACKGROUND

As maternal fever affects approximately 6-8% of early pregnancies, it is important to expand upon previous observations of an association between maternal fever and birth defects.

METHODS

We analyzed data from the National Birth Defects Prevention Study, a multistate, case-control study of major structural birth defects. Telephone interviews were completed by mothers of cases (n = 17,162) and controls (n = 10,127). Using multivariable logistic regression, we assessed the association between maternal self-report of cold or flu with fever and cold or flu without fever during early pregnancy and 30 categories of non-cardiac birth defects.

RESULTS

Maternal report of cold or flu with fever was significantly associated with 8 birth defects (anencephaly, spina bifida, encephalocele, cleft lip with or without cleft palate, colonic atresia/stenosis, bilateral renal agenesis/hypoplasia, limb reduction defects, and gastroschisis) with elevated adjusted odds ratios ranging from 1.2 to 3.7. Maternal report of cold or flu without fever was not associated with any of the birth defects studied.

CONCLUSIONS

This study adds to the evidence that maternal fever during early pregnancy is associated with an increased risk for selected birth defects. Elevated associations were limited to mothers who reported a fever, suggesting that it is fever that contributes to the excess risk rather than illnesses associated with it. However, fever may also serve as a marker for more severe infections.

Population-based case-control study of the association between weather-related extreme heat events and neural tube defects

BACKGROUND

Elevated body core temperature has been shown to have teratogenic effects in animal studies. Our study evaluated the association between weather-related extreme heat events (EHEs) in the summer season and neural tube defects (NTDs), and further investigated whether pregnant women with a high pregestational body mass index (BMI) have a greater risk of having a child with NTDs associated with exposure to EHE than women with a normal BMI.

METHODS

We conducted a population-based case-control study among mothers of infants with NTDs and mothers of infants without major birth defects, who participated in the National Birth Defects Prevention Study and had at least 1 day of the third or fourth week postconception during summer months. EHEs were defined using the 95th and the 90th percentiles of the daily maximum universal apparent temperature. Adjusted odds ratios and 95% confidence intervals were calculated using unconditional logistic regression models with Firth's penalized likelihood method while controlling for other known risk factors.

RESULTS

Overall, we did not observe a significant association between EHEs and NTDs. At the climate region level, consistently elevated but not statistically significant estimates were observed for at least 2 consecutive days with daily universal apparent maximum temperature above the 95th percentile of the UATmax distribution for the season, year, and weather monitoring station in New York (Northeast), North Carolina and Georgia (Southeast), and Iowa (Upper Midwest). No effect modification by BMI was observed.

CONCLUSION

EHEs occurring during the relevant developmental window of embryogenesis do not appear to appreciably affect the risk of NTDs. Future studies should refine exposure assessment, and more completely account for maternal activities that may modify the effects of weather exposure. Birth Defects Research 109:1482-1493, 2017.© 2017 Wiley Periodicals, Inc.

Clinical and risk factor analysis of cloacal defects in the National Birth Defects Prevention Study

Cloacal exstrophy (CE) and persistent cloaca (PC) (alternatively termed urorectal septum malformation sequence [URSMS]), represent two major cloacal defects (CDs). Clinical characteristics and risk factors often are studied for both defects combined, rather than exploring if these defects have different etiologies. We enumerated clinical features for 47 CE and 54 PC (inclusive of URSMS) cases from the National Birth Defects Prevention Study. Thirty-three CE cases were classified as isolated and 14 as multiple (presence of unassociated major defects); respective totals for PC cases were 26 and 28. We compared selected child and maternal characteristics between 11,829 non-malformed controls and CE and PC cases using chi-square or Fisher's exact tests. Compared to controls, CE and PC cases were statistically more likely (p < 0.05) to be preterm; CE cases were more likely to be multiple births. We conducted logistic regression analysis to estimate odds ratios and 95% confidence intervals for any CD, CE, and PC with selected self-reported maternal prepregnancy and periconceptional (one month prior to 3 months following conception) exposures. In crude and adjusted analyses, we observed significant positive associations for any CD, CE, and PC with use of any fertility medication or assisted reproductive technology procedure. Significant positive associations observed only in crude analyses were any CD with maternal obesity or use of progesterone, any CD and CE with any x-ray, and any CD and PC with use of folate antagonist medications. Our findings provide some of the first insights into potential differing etiologies for CE and PC.

Impact of sample collection participation on the validity of estimated measures of association in the National Birth Defects Prevention Study when assessing gene-environment interactions

To better understand the impact that nonresponse for specimen collection has on the validity of estimates of association, we examined associations between self-reported maternal periconceptional smoking, folic acid use, or pregestational diabetes mellitus and six birth defects among families who did and did not submit buccal cell samples for DNA following a telephone interview as part of the National Birth Defects Prevention Study (NBDPS). Analyses included control families with live born infants who had no birth defects (N = 9,465), families of infants with anorectal atresia or stenosis (N = 873), limb reduction defects (N = 1,037), gastroschisis (N = 1,090), neural tube defects (N = 1,764), orofacial clefts (N = 3,836), or septal heart defects (N = 4,157). Estimated dates of delivery were between 1997 and 2009. For each exposure and birth defect, odds ratios and 95% confidence intervals were calculated using logistic regression stratified by race-ethnicity and sample collection status. Tests for interaction were applied to identify potential differences between estimated measures of association based on sample collection status. Significant differences in estimated measures of association were observed in only four of 48 analyses with sufficient sample sizes. Despite lower than desired participation rates in buccal cell sample collection, this validation provides some reassurance that the estimates obtained for sample collectors and noncollectors are comparable. These findings support the validity of observed associations in gene-environment interaction studies for the selected exposures and birth defects among NBDPS participants who submitted DNA samples.

Paternal and joint parental occupational pesticide exposure and spina bifida in the National Birth Defects Prevention Study, 1997 to 2002

BACKGROUND

Because of persistent concerns over the association between pesticides and spina bifida, we examined the role of paternal and combined parental occupational pesticide exposures in spina bifida in offspring using data from a large population-based study of birth defects.

METHODS

Occupational information from fathers of 291 spina bifida cases and 2745 unaffected live born control infants with estimated dates of delivery from 1997 to 2002 were collected by means of maternal report. Two expert industrial hygienists estimated exposure intensity and frequency to insecticides, herbicides, and fungicides. Multivariable logistic regression models were used to estimate adjusted odds ratios (aOR) and 95% confidence intervals (CI) for exposure to any pesticide and to any class of pesticide (yes/no; and by median), and exposure to combinations of pesticides (yes/no) and risk of spina bifida. Adjusted odds ratios were also estimated by parent exposed to pesticides (neither, mother only, father only, both parents).

RESULTS

Joint parental occupational pesticide exposure was positively associated with spina bifida (aOR, 1.5; 95% CI, 0.9-2.4) when compared with infants with neither maternal nor paternal exposures; a similar association was not observed when only one parent was exposed. There was a suggested positive association between combined paternal insecticide and fungicide exposures and spina bifida (aOR, 1.5; 95% CI, 0.8-2.8), however, nearly all other aORs were close to unity.

CONCLUSION

Overall, there was little evidence paternal occupational pesticide exposure was associated with spina bifida. However, the small numbers make it difficult to precisely evaluate the role of pesticide classes, individually and in combination. Birth Defects Research (Part A) 106:963-971, 2016. © 2016 Wiley Periodicals, Inc.

Maternal autoimmune disease and birth defects in the National Birth Defects Prevention Study

BACKGROUND

Little is known about the association between maternal autoimmune disease or its treatment and the risk of birth defects. We examined these associations using data from the National Birth Defects Prevention Study, a multi-site, population-based, case-control study.

METHODS

Analyses included 25,116 case and 9897 unaffected control infants with estimated delivery dates between 1997 and 2009. Information on autoimmune disease, medication use, and other pregnancy exposures was collected by means of telephone interview. Adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were estimated for birth defects with five or more exposed cases; crude ORs and exact 95% CIs were estimated for birth defects with three to four exposed cases.

RESULTS

Autoimmune disease was reported by 373 mothers (279 case and 94 control mothers). The majority of birth defects evaluated were not associated with autoimmune disease; however, a statistically significant association between maternal autoimmune disease and encephalocele was observed (OR, 4.64; 95% CI, 1.95-11.04). Eighty-two mothers with autoimmune disease used an immune modifying/suppressing medication during pregnancy; this was associated with encephalocele (OR, 7.26; 95% CI, 1.37-24.61) and atrial septal defects (OR, 3.01; 95% CI, 1.16-7.80).

CONCLUSION

Our findings suggest maternal autoimmune disease and treatment are not associated with the majority of birth defects, but may be associated with some defects, particularly encephalocele. Given the low prevalence of individual autoimmune diseases and the rare use of specific medications, we were unable to examine associations of specific autoimmune diseases and medications with birth defects. Other studies are needed to confirm these findings. Birth Defects Research (Part A) 106:950-962, 2016. © 2016 Wiley Periodicals, Inc.

Association between antibiotic use among pregnant women with urinary tract infections in the first trimester and birth defects, National Birth Defects Prevention Study 1997 to 2011

BACKGROUND

Previous studies noted associations between birth defects and some antibiotics (e.g., nitrofurantoin, sulfonamides) but not others (e.g., penicillins). It is unclear if previous findings were due to antibiotic use, infections, or chance. To control for potential confounding by indication, we examined associations between antibiotic use and birth defects, among women reporting urinary tract infections (UTIs).

METHODS

The National Birth Defects Prevention Study is a multi-site, population-based case-control study. Case infants/fetuses have any of over 30 major birth defects and controls are live-born infants without major birth defects. We analyzed pregnancies from 1997 to 2011 to estimate the association between maternally reported periconceptional (month before conception through the third month of pregnancy) use of nitrofurantoin, trimethoprim-sulfamethoxazole, or cephalosporins and specific birth defects, among women with periconceptional UTIs. Women with periconceptional UTIs who reported penicillin use served as the comparator.

RESULTS

Periconceptional UTIs were reported by 7.8% (2029/26,068) of case and 6.7% (686/10,198) of control mothers. Most (68.2% of case, 66.6% of control mothers) also reported antibiotic use. Among 608 case and 231 control mothers reporting at least one periconceptional UTI and certain antibiotic use, compared with penicillin, nitrofurantoin use was associated with oral clefts in the offspring (adjusted odds ratio, 1.97 [95% confidence interval, 1.10-3.53]), trimethoprim-sulfamethoxazole use with esophageal atresia (5.31 [1.39-20.24]) and diaphragmatic hernia (5.09 [1.20-21.69]), and cephalosporin use with anorectal atresia/stenosis (5.01 [1.34-18.76]).

CONCLUSION

Periconceptional exposure to some antibiotics might increase the risk for certain birth defects. However, because individual birth defects are rare, absolute risks should drive treatment decisions.Birth Defects Research (Part A) 106:940-949, 2016.© 2016 Wiley Periodicals, Inc.

Malformations Surveillance: Comparison between Findings at Birth and Age 1 Year

BACKGROUND

Malformations surveillance programs among newborn infants are used to determine the prevalence of congenital anomalies. A comparison in the same group of infants between the malformations detected at birth and those detected at 1 year of age will identify errors in the surveillance process and, also, the abnormalities more likely not to be detected at birth, but later in the first year of life.

METHODS

The malformations identified at birth by Brigham and Women's Hospital (BWH) in the years 2000 and 2005 have been compared with the abnormalities detected in the same infants up to age 1 year by the Massachusetts Birth Defects Monitoring Program.

RESULTS

The Massachusetts Birth Defects Monitoring Program identified 557 malformed infants in 2000 and 415 in 2005. Of these, 34 (3.5%) of the malformed infants were missed at birth by BWH Surveillance Program. An additional 22 (2.3%) malformed infants had delayed detection, as they were identified later in the first year. The reasons were the fact that: (1) the Surveillance staff reviewed the physicians' recorded findings only on the first day of life; (2) failure of the examining pediatrician to record the presence of a malformation in her/his notes. The most common abnormalities with delayed detection were mild heart defects, such as atrial septal defects.

CONCLUSION

These findings emphasize the importance in a newborn malformations surveillance program of continued follow up in the first days of life, especially in small, premature infants. Birth Defects Research 110:142-147, 2018. © 2017 Wiley Periodicals, Inc.

Estimated Maternal Pesticide Exposure from Drinking Water and Heart Defects in Offspring

Our objective was to examine the relationship between estimated maternal exposure to pesticides in public drinking water and the risk of congenital heart defects (CHD). We used mixed-effects logistic regression to analyze data from 18,291 nonsyndromic cases with heart defects from the Texas Birth Defects Registry and 4414 randomly-selected controls delivered in Texas from 1999 through 2005. Water district-level pesticide exposure was estimated by linking each maternal residential address to the corresponding public water supply district’s measured atrazine levels. We repeated analyses among independent subjects from the National Birth Defects Prevention Study (NBDPS) (1620 nonsyndromic cases with heart defects and 1335 controls delivered from 1999 through 2005). No positive associations were observed between high versus low atrazine level and eight CHD subtypes or all included heart defects combined. These findings should be interpreted with caution, in light of potential misclassification and relatively large proportions of subjects with missing atrazine data. Thus, more consistent and complete monitoring and reporting of drinking water contaminants will aid in better understanding the relationships between pesticide water contaminants and birth defects.

Pediatric cancer risk in association with birth defects: A systematic review

BACKGROUND

Many epidemiological studies have examined associations between birth defects (BDs) and pediatric malignancy over the past several decades. Our objective was to conduct a systematic literature review of studies reporting on this association.

METHODS

We used librarian-designed searches of the PubMed Medline and Embase databases to identify primary research articles on pediatric neoplasms and BDs. English language articles from PubMed and Embase up to 10/12/2015, and in PubMed up to 5/12/2017 following an updated search, were eligible for inclusion if they reported primary epidemiological research results on associations between BDs and pediatric malignancies. Two reviewers coded each article based on the title and abstract to identify eligible articles that were abstracted using a structured form. Additional articles were identified through reference lists and other sources. Results were synthesized for pediatric cancers overall and for nine major pediatric cancer subtypes.

RESULTS

A total of 14,778 article citations were identified, of which 80 met inclusion criteria. Pediatric cancer risk was increased in most studies in association with BDs overall with some notable specific findings, including increased risks for CNS tumors in association with CNS abnormalities and positive associations between rib anomalies and several pediatric cancer types.

CONCLUSIONS

Some children born with BDs may be at increased risk for specific pediatric malignancy types. This work provides a foundation for future investigations that are needed to clarify specific BD types predisposing toward malignancy and possible underlying causes of both BDs and malignancy.

Multidisciplinary care of craniosynostosis

The management of craniosynostosis, especially in the setting of craniofacial syndromes, is ideally done in a multidisciplinary clinic with a team focused toward comprehensive care. Craniosynostosis is a congenital disorder of the cranium, caused by the premature fusion of one or more cranial sutures. This fusion results in abnormal cranial growth due to the inability of the involved sutures to accommodate the growing brain. Skull growth occurs only at the patent sutures, resulting in an abnormal head shape. If cranial growth is severely restricted, as seen in multisuture craniosynostosis, elevation in intracranial pressure can occur. Whereas most patients treated in a multidisciplinary craniofacial clinic have non-syndromic or isolated craniosynostosis, the most challenging patients are those with syndromic craniosynostosis. The purpose of this article was to discuss the multidisciplinary team care required to treat both syndromic and non-syndromic craniosynostosis.

Maternal occupational physical activity and risk for orofacial clefts

OBJECTIVES

To perform a case-control study of maternal occupational physical activity and risk for orofacial clefts in Texas during 1999-2009.

METHODS

We used logistic regression to assess 14 measures of physical activity estimated from a job exposure matrix, using the maternal occupation reported on the birth certificate, among 887 children with cleft lip with or without cleft palate (CLP), 436 children with cleft palate only (CP), and 1932 controls.

RESULTS

After adjusting for several potential confounders, seven measures of physical activity (as a categorical and/or continuous variable) were significantly associated with CLP, CP, or both. Positive associations were seen for keeping balance, kneeling, standing, and walking/running (odds ratio 95% confidence interval range 1.0-1.9 for fourth versus first quartile). A significant positive trend was also seen for bending/twisting. Negative associations were seen for repetitive motion and sitting.

CONCLUSIONS

Maternal occupational physical activity may be related to the etiology of orofacial clefts.

Childhood cancer risk in those with chromosomal and non-chromosomal congenital anomalies in Washington State: 1984-2013

Background

The presence of a congenital anomaly is associated with increased childhood cancer risk, likely due to large effects of Down syndrome and chromosomal anomalies for leukemia. Less is known about associations with presence of non-chromosomal anomalies.

Methods

Records of children diagnosed with cancer at <20 years of age during 1984–2013 in Washington State cancer registries were linked to their birth certificates (N = 4,105). A comparison group of children born in the same years was identified. Congenital anomalies were assessed from birth records and diagnosis codes in linked hospital discharge data. Logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (CI) for cancer, and for specific cancer types in relation to the presence of any anomaly and specific anomalies.

Results

Having any congenital anomaly was associated with an increased risk of childhood cancer (OR: 1.46, 95% CI 1.28–1.65). Non-chromosomal anomalies were also associated with increased childhood cancer risk overall (OR: 1.35; 95% CI: 1.18–1.54), and with increased risk of several cancer types, including neuroblastoma, renal, hepatoblastoma, soft-tissue sarcoma, and germ cell tumors. Increasing number of non-chromosomal anomalies was associated with a stronger risk of childhood cancer (OR for 3+ anomalies: 3.11, 95% CI: 1.54–6.11). Although central nervous system (CNS) anomalies were associated with CNS tumors (OR: 6.05, 95% CI 2.75–13.27), there was no strong evidence of other non-chromosomal anomalies being specifically associated with cancer occurring in the same organ system or anatomic location.

Conclusions

Non-chromosomal anomalies increased risk of several cancer types. Additionally, we found that increasing number of non-chromosomal anomalies was associated with a stronger risk of cancer. Pooling similar data from many regions would increase power to identify specific associations in order to inform molecular studies examining possible common developmental pathways in the etiologies of birth defects and cancer.

Etiology and clinical presentation of birth defects: population based study

Objective To assess causation and clinical presentation of major birth defects.Design Population based case cohort.Setting Cases of birth defects in children born 2005-09 to resident women, ascertained through Utah's population based surveillance system. All records underwent clinical re-review.Participants 5504 cases among 270 878 births (prevalence 2.03%), excluding mild isolated conditions (such as muscular ventricular septal defects, distal hypospadias).Main outcome measures The primary outcomes were the proportion of birth defects with a known etiology (chromosomal, genetic, human teratogen, twinning) or unknown etiology, by morphology (isolated, multiple, minors only), and by pathogenesis (sequence, developmental field defect, or known pattern of birth defects).Results Definite cause was assigned in 20.2% (n=1114) of cases: chromosomal or genetic conditions accounted for 94.4% (n=1052), teratogens for 4.1% (n=46, mostly poorly controlled pregestational diabetes), and twinning for 1.4% (n=16, conjoined or acardiac). The 79.8% (n=4390) remaining were classified as unknown etiology; of these 88.2% (n=3874) were isolated birth defects. Family history (similarly affected first degree relative) was documented in 4.8% (n=266). In this cohort, 92.1% (5067/5504) were live born infants (isolated and non-isolated birth defects): 75.3% (4147/5504) were classified as having an isolated birth defect (unknown or known etiology).Conclusions These findings underscore the gaps in our knowledge regarding the causes of birth defects. For the causes that are known, such as smoking or diabetes, assigning causation in individual cases remains challenging. Nevertheless, the ongoing impact of these exposures on fetal development highlights the urgency and benefits of population based preventive interventions. For the causes that are still unknown, better strategies are needed. These can include greater integration of the key elements of etiology, morphology, and pathogenesis into epidemiologic studies; greater collaboration between researchers (such as developmental biologists), clinicians (such as medical geneticists), and epidemiologists; and better ways to objectively measure fetal exposures (beyond maternal self reports) and closer (prenatally) to the critical period of organogenesis.

Chromosome microarray analysis in the investigation of children with congenital heart disease

BACKGROUND

Our study was aimed to explore the clinical implication of chromosome microarray analysis (CMA) in genetically etiological diagnosis of children with congenital heart disease (CHD).

METHODS

A total of 104 children with CHD with or without multiple congenital anomalies (MCA) or intellectual disabilities/developmental delay (ID/DD) but normal karyotype were investigated using Affymetrix CytoScan HD array.

RESULT

Pathogenic copy number variations (PCNVs) were identified in 29 children (27.9%). The detection rates in children with simple CHD and complex CHD were 31.1% (19/61) and 23.2% (10/43), respectively. The detection rates of PCNVs were 17.9% (7/39), 20% (5/25), 63.2% (12/19) and 23.8% (5/21) in isolated CHD, CHD plus MCA, CHD plus ID/DD, CHD plus MCA and ID/DD, respectively. The PCNVs rate of CHD plus ID/DD was significantly higher than that of isolated CHD. Two genomic loci including 15q11.2 deletion and 1q43-q44 deletion were considered as CHD locus. The DVL1, SKI, STIM1, CTNNA3 and PLN were identified as candidate genes associated with CHD phenotypes.

CONCLUSION

CMA can increase the diagnostic rate and improve the etiological diagnosis in children with CHD. We suggest CMA as a first-tier test in children with CHD, especially in children with CHD plus ID/DD.

Identifying birth defects in automated data sources in the Vaccine Safety Datalink

PURPOSE

The Vaccine Safety Datalink (VSD), a collaboration between the Centers for Disease Control and Prevention and several large healthcare organizations, aims to monitor safety of vaccines administered in the USA. We present definitions and prevalence estimates for major structural birth defects to be used in studies of maternal vaccine safety.

METHODS

In this observational study, we created and refined algorithms for identifying major structural birth defects from electronic healthcare data, conducted formal chart reviews for severe cardiac defects, and conducted limited chart validation for other defects. We estimated prevalence for selected defects by VSD site and birth year and compared these estimates to those in a US and European surveillance system.

RESULTS

We developed algorithms to enumerate >50 major structural birth defects from standardized administrative and healthcare data based on utilization patterns and expert opinion, applying criteria for number, timing, and setting of diagnoses. Our birth cohort included 497 894 infants across seven sites. The period prevalence for all selected major birth defects in the VSD from 2004 to 2013 was 1.7 per 100 live births. Cardiac defects were most common (65.4 per 10 000 live births), with one-fourth classified as severe, requiring emergent intervention. For most major structural birth defects, prevalence estimates were stable over time and across sites and similar to those reported in other population-based surveillance systems.

CONCLUSIONS

Our algorithms can efficiently identify many major structural birth defects in large healthcare datasets and can be used in studies evaluating the safety of vaccines administered to pregnant women. Copyright © 2017 John Wiley & Sons, Ltd.

Clinician's Primer to ICD-10-CM Coding for Cleft Lip/Palate Care

On October 1,2015, the United States required use of the Clinical Modification of the International Classification of Diseases, 10th Revision (ICD-10-CM) for diagnostic coding. This primer was written to assist the cleft care community with understanding and use of ICD-10-CM for diagnostic coding related to cleft lip and/or palate (CL/P).

No increased risk of major congenital anomalies or adverse pregnancy or neonatal outcomes following letrozole use in assisted reproductive technology

STUDY QUESTION

Does letrozole use increase the risk of major congenital anomalies and adverse pregnancy and neonatal outcomes in fresh, single-embryo transfer?

SUMMARY ANSWER

Letrozole significantly decreases the risk of miscarriage and does not increase the risk of major congenital anomalies or adverse pregnancy or neonatal outcomes compared with natural cycles in patients undergoing ART.

WHAT IS KNOWN ALREADY

Letrozole is the most commonly used aromatase inhibitor for mild ovarian stimulation in ART. However, its safety in terms of pregnancy and neonatal outcomes is unclear.

STUDY DESIGN SIZE, DURATION

This retrospective cohort study used data from the Japanese national ART registry from 2011 to 2013.

PARTICIPANTS/MATERIALS, SETTING, METHODS

A total of 3136 natural cycles and 792 letrozole-induced cycles associated with fresh, single-embryo transfer and resulting in a clinical pregnancy were included in the analysis. The main pregnancy outcomes were miscarriage, ectopic pregnancy and still birth, and the neonatal outcomes were preterm delivery, low birth weight, small/large for gestational age and major congenital anomalies. Terminated pregnancies were included in the analysis of major congenital anomalies. Odds ratios (ORs) and 95% CIs were calculated using multivariate logistic regression analysis adjusted for maternal age and calendar year.

MAIN RESULTS AND THE ROLE OF CHANCE

The risk of miscarriage was significantly lower in women administered letrozole (adjusted OR [aOR], 0.37, 95% CI, 0.30-0.47, P < 0.001). There was no significant difference in the overall risk of major congenital anomalies between the two groups (natural cycle 1.5% vs letrozole 1.9%, aOR, 1.24, 95% CI, 0.64-2.40, P = 0.52), and no increased risk for any specific organ system. Subgroup analysis demonstrated that the risk of major congenital anomalies was not increased in patients who underwent either in vitro fertilization or ICSI, or in those who received early cleavage stage or blastocyst embryo transfer. All other pregnancy and neonatal outcomes were comparable between the two groups.

LIMITATIONS REASONS FOR CAUTION

Despite the large sample size, we were only able to rule out the possibility that letrozole might cause large increases in birth-defect risks in ART patients.

WIDER IMPLICATIONS OF THE FINDINGS

The results suggest that letrozole stimulation reduces the risk of miscarriage, with no increase in the risk of major congenital anomalies or adverse pregnancy or neonatal outcomes compared with natural cycles in women undergoing ART. Letrozole may thus be a safe option for mild ovarian stimulation.

STUDY FUNDING/COMPETING INTERESTS

None.

TRIAL REGISTRATION NUMBER

Not applicable.

Comparison of environmental risk factors for esophageal atresia, anorectal malformations, and the combined phenotype in 263 German families

Esophageal atresia with or without tracheoesophageal fistula (EA/TEF) and anorectal malformations (ARM) represent the severe ends of the fore- and hindgut malformation spectra. Previous research suggests that environmental factors are implicated in their etiology. These risk factors might indicate the influence of specific etiological mechanisms on distinct developmental processes (e.g. fore- vs. hindgut malformation). The present study compared environmental factors in patients with isolated EA/TEF, isolated ARM, and the combined phenotype during the periconceptional period and the first trimester of pregnancy in order to investigate the hypothesis that fore- and hindgut malformations involve differing environmental factors. Patients with isolated EA/TEF (n = 98), isolated ARM (n = 123), and the combined phenotype (n = 42) were included. Families were recruited within the context of two German multicenter studies of the genetic and environmental causes of EA/TEF (great consortium) and ARM (CURE-Net). Exposures of interest were ascertained using an epidemiological questionnaire. Chi-square, Fisher's exact, and Mann-Whitney U-tests were used to assess differences between the three phenotypes. Newborns with isolated EA/TEF and the combined phenotype had significantly lower birth weights than newborns with isolated ARM (P = 0.001 and P < 0.0001, respectively). Mothers of isolated EA/TEF consumed more alcohol periconceptional (80%) than mothers of isolated ARM or the combined phenotype (each 67%). Parental smoking (P = 0.003) and artificial reproductive techniques (P = 0.03) were associated with isolated ARM. Unexpectedly, maternal periconceptional multivitamin supplementation was most frequent among patients with the most severe form of disorder, i.e. the combined phenotype (19%). Significant differences in birth weight were apparent between the three phenotype groups. This might be attributable to the limited ability of EA/TEF fetuses to swallow amniotic fluid, thus depriving them of its nutritive properties. Furthermore, the present data suggest that fore- and hindgut malformations involve differing environmental factors. Maternal periconceptional multivitamin supplementation was highest among patients with the combined phenotype. This latter finding is contrary to expectation, and warrants further analysis in large prospective epidemiological studies.

Associations between maternal periconceptional exposure to secondhand tobacco smoke and major birth defects

BACKGROUND

While associations between secondhand smoke and a few birth defects (namely, oral clefts and neural tube defects) have been noted in the scientific literature, to our knowledge, there is no single or comprehensive source of population-based information on its associations with a range of birth defects among nonsmoking mothers.

OBJECTIVE

We utilized data from the National Birth Defects Prevention Study, a large population-based multisite case-control study, to examine associations between maternal reports of periconceptional exposure to secondhand smoke in the household or workplace/school and major birth defects.

STUDY DESIGN

The multisite National Birth Defects Prevention Study is the largest case-control study of birth defects to date in the United States. We selected cases from birth defect groups having >100 total cases, as well as all nonmalformed controls (10,200), from delivery years 1997 through 2009; 44 birth defects were examined. After excluding cases and controls from multiple births and whose mothers reported active smoking or pregestational diabetes, we analyzed data on periconceptional secondhand smoke exposure-encompassing the period 1 month prior to conception through the first trimester. For the birth defect craniosynostosis, we additionally examined the effect of exposure in the second and third trimesters as well due to the potential sensitivity to teratogens for this defect throughout pregnancy. Covariates included in all final models of birth defects with ≥5 exposed mothers were study site, previous live births, time between estimated date of delivery and interview date, maternal age at estimated date of delivery, race/ethnicity, education, body mass index, nativity, household income divided by number of people supported by this income, periconceptional alcohol consumption, and folic acid supplementation. For each birth defect examined, we used logistic regression analyses to estimate both crude and adjusted odds ratios and 95% confidence intervals for both isolated and total case groups for various sources of exposure (household only; workplace/school only; household and workplace/school; household or workplace/school).

RESULTS

The prevalence of secondhand smoke exposure only across all sources ranged from 12.9-27.8% for cases and 14.5-15.8% for controls. The adjusted odds ratios for any vs no secondhand smoke exposure in the household or workplace/school and isolated birth defects were significantly elevated for neural tube defects (anencephaly: adjusted odds ratio, 1.66; 95% confidence interval, 1.22-2.25; and spina bifida: adjusted odds ratio, 1.49; 95% confidence interval, 1.20-1.86); orofacial clefts (cleft lip without cleft palate: adjusted odds ratio, 1.41; 95% confidence interval, 1.10-1.81; cleft lip with or without cleft palate: adjusted odds ratio, 1.24; 95% confidence interval, 1.05-1.46; cleft palate alone: adjusted odds ratio, 1.31; 95% confidence interval, 1.06-1.63); bilateral renal agenesis (adjusted odds ratio, 1.99; 95% confidence interval, 1.05-3.75); amniotic band syndrome-limb body wall complex (adjusted odds ratio, 1.66; 95% confidence interval, 1.10-2.51); and atrial septal defects, secundum (adjusted odds ratio, 1.37; 95% confidence interval, 1.09-1.72). There were no significant inverse associations observed.

CONCLUSION

Additional studies replicating the findings are needed to better understand the moderate positive associations observed between periconceptional secondhand smoke and several birth defects in this analysis. Increased odds ratios resulting from chance (eg, multiple comparisons) or recall bias cannot be ruled out.

Gene variants as risk factors for gastroschisis

In a population‐based case‐control study in California of 228 infants, we investigated 75 genetic variants in 20 genes and risk of gastroschisis with regard to maternal age, race/ethnicity, vitamin use, and smoking exposure. We hypothesized that genes related to vascular compromise may interact with environmental factors to affect the risk of gastroschisis. Haplotypes were constructed for 75 gene variants using the HaploView program. Risk for gastroschisis associated with each gene variant was calculated for both the homozygotes and the heterozygotes, with the homozygous wildtypes as the referent. Risks were estimated as odds ratios (ORs) with 95% confidence intervals (CIs) by logistic regression. We found 11 gene variants with increased risk and four variants with decreased risk of gastroschisis for heterozygous (OR_h) or homozygous variants (OR_v) genotypes. These included NOS3 (rs1036145) OR_h = 0.4 (95% CI: 0.2–0.7); NOS3 (rs10277237) OR_v = 2.7 (95% CI: 1.3–6.0); ADD1 (rs12503220) OR_h = 2.9 (95% CI: 1.6–5.4), GNB3 (rs5443) OR_h = 0.2 (95% CI: 0.1–0.5), OR_v = 0.4 (95% CI: 0.2–0.9); ICAM1 (rs281428) OR_v = 6.9 (95% CI: 2.1–22.9), ICAM1 (rs3093030) OR_v = 2.6 (95% CI: 1.2–5.6); ICAM4 (rs281438) OR_v = 4.9 (95% CI: 1.4–16.6), ICAM5 (rs281417) OR_h = 2.1 (95% CI: 1.1–4.1), OR_v = 4.8 (95% CI: 1.7–13.6); ICAM5 (rs281440) OR_h = 23.7 (95% CI: 5.5–102.5), OR_v = 20.6 (95% CI: 3.4–124.3); ICAM5 (rs2075741) OR_v = 2.2 (95% CI: 1.1–4.4); NAT1 OR_v = 0.3 (95% CI: 0.1–0.9). There were additional associations between several gene variants and gastroschisis among women aged 20–24 and among mothers with and without vitamin use. NOS3, ADD1, ICAM1, ICAM4, and ICAM5 warrant further investigation in additional populations and with the interaction of additional environmental exposures. © 2016 Wiley Periodicals, Inc.

Maternal hypertension and risk for hypospadias in offspring

Hypospadias is one of the most common birth defects in male infants. Maternal hypertension is a suspected risk factor; however, few previous studies have addressed the possibility of reporting bias, and several previous studies have not accounted for hypospadias severity. We analyzed data from the Texas Birth Defects Registry for 10,924 nonsyndromic cases and statewide vital records for deliveries during 1999-2009, using Poisson regression. After adjustment for potential confounders, hypospadias was associated with maternal hypertension (adjusted prevalence ratio: 1.5, 95% confidence interval: 1.4-1.7). Similar associations were observed with gestational and pregestational hypertension, including separate analyses restricted to the subset of cases with severe (second- or third-degree) hypospadias. All of these associations were also similar among the subset of cases with isolated hypospadias (without additional birth defects). To evaluate the potential for bias due to potential hypertension misclassification, we repeated our analyses using logistic regression, comparing the cases to controls with other birth defects. In these analyses, the associations with gestational hypertension were similar, but adjusted associations with pregestational hypertension were no longer observed. Our findings support an association between gestational hypertension and hypospadias in offspring, but also suggest that previously observed associations with pregestational hypertension may have been inflated due to differential misclassification of hypertension (e.g., reporting bias). As gestational hypertension is recognized after hypospadias development, more research is needed to determine if this association reflects an increase in gestational hypertension risk secondary to hypospadias or if both conditions have shared risk factors (e.g., precursors of gestational hypertension). © 2016 Wiley Periodicals, Inc.