Real-world data are not always big data: the case for primary data collection on medication use in pregnancy in the context of birth defects research.

Many examples of the use of real-world data in the area of pharmacoepidemiology include "big data," such as insurance claims, medical records, or hospital discharge databases. However, "big" is not always better, particularly when studying outcomes with narrow windows of etiologic relevance. Birth defects are such an outcome, for which specificity of exposure timing is critical. Studies with primary data collection can be designed to query details about the timing of medication use, as well as type, dose, frequency, duration, and indication, that can better characterize the "real world." Because birth defects are rare, etiologic studies are typically case­control in design, like the National Birth Defects Prevention Study, Birth Defects Study to Evaluate Pregnancy Exposures, and Slone Birth Defects Study. Recall bias can be a concern, but the ability to collect detailed information about both prescription and over-the-counter medication use and other exposures such as diet, family history, and sociodemographic factors is a distinct advantage over claims and medical record data sources. Case­control studies with primary data collection are essential to advancing the pharmacoepidemiology of birth defects. This article is part of a Special Collection on Pharmacoepidemiology.

Maternal exposure to zolpidem and risk of specific birth defects.

Zolpidem is a non-benzodiazepine agent indicated for treatment of insomnia. While zolpidem crosses the placenta, little is known about its safety in pregnancy. We assessed associations between self-reported zolpidem use 1 month before pregnancy through to the end of the third month ("early pregnancy") and specific birth defects using data from two multi-site case-control studies: National Birth Defects Prevention Study and Slone Epidemiology Center Birth Defects Study. Analysis included 39,711 birth defect cases and 23,035 controls without a birth defect. For defects with ≥ 5 exposed cases, we used logistic regression with Firth's penalised likelihood to estimate adjusted odds ratios and 95% confidence intervals, considering age at delivery, race/ethnicity, education, body mass index, parity, early-pregnancy antipsychotic, anxiolytic, antidepressant use, early-pregnancy opioid use, early-pregnancy smoking, and study as potential covariates. For defects with three-four exposed cases, we estimated crude odds ratios and 95% confidence intervals. Additionally, we explored differences in odds ratios using propensity score-adjustment and conducted a probabilistic bias analysis of exposure misclassification. Overall, 84 (0.2%) cases and 46 (0.2%) controls reported early-pregnancy zolpidem use. Seven defects had sufficient sample size to calculate adjusted odds ratios, which ranged from 0.76 for cleft lip to 2.18 for gastroschisis. Four defects had odds ratios > 1.8. All confidence intervals included the null. Zolpidem use was rare. We could not calculate adjusted odds ratios for most defects and estimates are imprecise. Results do not support a large increase in risk, but smaller increases in risk for certain defects cannot be ruled out.

Associations between maternal periconceptional alcohol consumption and risk of omphalocele among offspring, National Birth Defects Prevention Study, 1997-2011.

OBJECTIVE: Previous studies of alcohol consumption during pregnancy and omphalocele have produced mixed results. We updated an earlier analysis of National Birth Defects Prevention Study (NBDPS) data, adding six years of participants, to examine associations between maternal alcohol consumption and omphalocele. METHODS: NBDPS was a multi-site, population-based case-control study in the United States. Cases were identified from birth defect surveillance programs in 10 states; controls were liveborn infants without a birth defect randomly selected from the same catchment areas. Mothers self-reported alcohol consumption during the periconceptional period (one month before through the third gestational month) via telephone interview. Our study included mothers of 410 omphalocele cases and 11,219 controls with estimated dates of delivery (EDDs) during 1997-2011. We used logistic regression to estimate adjusted odds ratios (AORs) and 95% confidence intervals (CIs) for periconceptional alcohol consumption and omphalocele. We performed a probabilistic bias analysis to evaluate the impact of alcohol exposure misclassification on our results. RESULTS: Overall, 44% of case and 38% of control mothers reported periconceptional alcohol consumption; 22% and 17%, respectively, reported binge drinking. Any maternal periconceptional alcohol consumption was associated with modestly increased odds of omphalocele (AOR 1.35, 95% CI 1.09, 1.68), as was binge drinking (AOR 1.47, 95% CI 1.08, 2.01). Our bias analysis yielded estimates further from the null. CONCLUSIONS: We observed modest associations between maternal periconceptional alcohol consumption and omphalocele. Based on our bias analysis, studies of alcohol and birth defects not accounting for exposure misclassification may underestimate associations.

Bias analyses to investigate the impact of differential participation: Application to a birth defects case-control study.

BACKGROUND: Certain associations observed in the National Birth Defects Prevention Study (NBDPS) contrasted with other research or were from areas with mixed findings, including no decrease in odds of spina bifida with periconceptional folic acid supplementation, moderately increased cleft palate odds with ondansetron use and reduced hypospadias odds with maternal smoking. OBJECTIVES: To investigate the plausibility and extent of differential participation to produce effect estimates observed in NBDPS. METHODS: We searched the literature for factors related to these exposures and participation and conducted deterministic quantitative bias analyses. We estimated case-control participation and expected exposure prevalence based on internal and external reports, respectively. For the folic acid-spina bifida and ondansetron-cleft palate analyses, we hypothesized the true odds ratio (OR) based on prior studies and quantified the degree of exposure over- (or under-) representation to produce the crude OR (cOR) in NBDPS. For the smoking-hypospadias analysis, we estimated the extent of selection bias needed to nullify the association as well as the maximum potential harmful OR. RESULTS: Under our assumptions (participation, exposure prevalence, true OR), there was overrepresentation of folic acid use and underrepresentation of ondansetron use and smoking among participants. Folic acid-exposed spina bifida cases would need to have been ≥1.2× more likely to participate than exposed controls to yield the observed null cOR. Ondansetron-exposed cleft palate cases would need to have been 1.6× more likely to participate than exposed controls if the true OR is null. Smoking-exposed hypospadias cases would need to have been ≥1.2 times less likely to participate than exposed controls for the association to falsely appear protective (upper bound of selection bias adjusted smoking-hypospadias OR = 2.02). CONCLUSIONS: Differential participation could partly explain certain associations observed in NBDPS, but questions remain about why. Potential impacts of other systematic errors (e.g. exposure misclassification) could be informed by additional research.

Antifungal medication use during pregnancy and the risk of selected major birth defects in the National Birth Defects Prevention Study, 1997-2011.

PURPOSE: Recent studies suggest increased birth defect risk associated with maternal use of specific oral antifungals. We estimated associations between first-trimester antifungal use and selected non-cardiac birth defects using National Birth Defects Prevention Study (NBDPS) data. METHODS: Participants with a pregnancy affected by a study-eligible birth defect ("cases") were ascertained from 10 birth defect surveillance programs; participants who delivered livebirths without a major birth defect ("controls") were randomly selected from birth records or hospital discharge lists. First-trimester antifungal use was self-reported via maternal interview. We estimated adjusted odds ratios (ORs) and 95% confidence intervals (CIs) for birth defects with ≥5 exposed cases using logistic regression. We estimated crude ORs and exact 95% CIs for birth defects with 3-4 exposed cases. Additionally, we conducted a probabilistic bias analysis of exposure misclassification. RESULTS: Our analysis included 19 624 cases and 11 427 controls; 257 (1.3%) cases and 123 (1.1%) controls reported first-trimester antifungal use. Of those who reported antifungals, 62.6% of cases and 64.2% of controls reported topical antifungals; 10.1% of cases and 4.9% of controls reported oral antifungals. We observed the strongest associations for encephalocele and Dandy-Walker malformation and modestly elevated estimates for several other defects. Bias-adjusted estimates were similar to the main analysis. CONCLUSION: First-trimester antifungal use was positively associated with several birth defects in our analysis, although CIs were imprecise. Further study is warranted to investigate associations between antifungal use and birth defects, including potential bias due to confounding by indication.

Maternal cyclobenzaprine exposure and risk of birth defects in the National Birth Defects Prevention Study (1997-2011) and Birth Defects Study to Evaluate Pregnancy exposureS (2014-2018).

PURPOSE: Cyclobenzaprine is a muscle relaxant indicated for acute pain. Little is known about cyclobenzaprine's safety during pregnancy. We explored the association between maternal cyclobenzaprine exposure and risk of birth defects among offspring. METHODS: We combined data from two large, multi-site, population-based case-control studies in the United States. Cases were identified from birth defects registries across 10 states; controls were liveborn infants without birth defects randomly selected from the same catchment areas. Participants reported cyclobenzaprine use during the month before conception through the third month of pregnancy ("periconception") via computer-assisted telephone interview. We used logistic regression to assess associations between periconceptional cyclobenzaprine exposure and selected structural birth defects. We calculated crude odds ratios (OR) with corresponding 95% confidence intervals (CI). RESULTS: Our study included 33 615 cases and 13 110 controls. Overall, 51 case (0.15%) and 9 control (0.07%) participants reported periconceptional cyclobenzaprine use. We observed increased risk for all seven defects with ≥3 exposed cases: cleft palate (OR = 4.79, 95% CI 1.71-13.44), cleft lip (OR = 2.50, 95% CI 0.89-7.02), anorectal atresia/stenosis (OR = 6.91, 95% CI 1.67, 28.65), d-transposition of the great arteries (OR = 6.97, 95% CI 2.17-22.36), coarctation of the aorta (OR = 5.58, 95% CI 1.88-16.58), pulmonary valve stenosis (OR = 4.55, 95% CI 1.10-18.87), and secundum atrial septal defect (OR = 3.08, 95% CI 0.83-11.45). CONCLUSIONS: Even in our large sample, cyclobenzaprine use was rare. Our estimates are unadjusted and imprecise so should be interpreted cautiously. These hypothesis-generating results warrant confirmation and further research to explore possible mechanisms.

Descriptive and risk factor analysis of infantile cataracts: National Birth Defects Prevention Study, 2000-2011.

Using National Birth Defects Prevention Study (NBDPS) data, we sought to estimate birth prevalence, describe clinical characteristics, and examine risk factors for infantile cataracts. We calculated birth prevalence using the numbers of NBDPS-eligible cataract cases and live births in the study area. We described case infants by the presence of associated ipsilateral eye defects (IEDs) and non-eye-related major birth defects. Using maternal exposure information collected via telephone interview, we conducted logistic regression analyses among the interviewed cases and controls. Birth prevalence of infantile cataracts was 1.07/10,000 live births. Unilateral cataracts were more often associated with IEDs, while infants with bilateral cataracts were more often preterm, full-term with low birth weight, or had non-eye-related major birth defects. Unilateral cataracts were positively associated with maternal nulliparity (adjusted odds ratio [aOR] = 1.61, 95% confidence interval [CI] = 1.18, 2.20; reference: multiparity), whereas bilateral cataracts were positively associated with maternal education <12 years (aOR = 2.08, 95% CI = 1.13, 3.82; reference: education >12 years), and foreign-born nativity (aOR = 1.92, 95% CI = 1.04, 3.52; reference: U.S.-born nativity). The current analysis can inform future epidemiological studies aimed at identifying mechanisms underlying the associations between infantile cataracts and complex maternal exposures, such as lower levels of education and foreign-born nativity.

Delayed entry into prenatal care among women with pre-pregnancy health conditions, National Birth Defects Prevention Study, 1997-2011.

First trimester entry into prenatal care is recommended for all women, and especially women with pre-pregnancy conditions. Our objective was to determine whether women with pre-pregnancy conditions were at lower risk of entry after the first trimester (delayed entry) into prenatal care than women without a pre-pregnancy health condition. We used data from 10,890 participants in the National Birth Defects Prevention Study who delivered liveborn infants without birth defects. Women reported pre-pregnancy conditions and timing of entry into prenatal care during a computer-assisted telephone interview. Multivariable logistic regression analyses were conducted to evaluate whether having a pre-pregnancy condition was associated with delayed entry into prenatal care compared to women without pre-pregnancy conditions. Approximately 13% of women reported delayed entry into prenatal care, and 18% of women reported a pre-pregnancy condition. Delayed entry into prenatal care was not associated with pre-pregnancy cardiometabolic or neurologic conditions. Women with thyroid conditions were less likely to report delayed entry into prenatal care (prevalence odds ratio (OR), 95% confidence interval (CI): 0.55 [0.32, 0.94]), but women with hematologic and respiratory conditions were more likely to report delayed entry into prenatal care (OR: 1.95 [1.00, 3.82] and 1.27 [0.95, 1.72], respectively), compared to those without any chronic conditions. Future research investigating the success of early prenatal care among women with thyroid conditions could identify ways to reduce delayed prenatal care among women with other pre-pregnancy conditions.

Maternal periconceptional alcohol consumption and gastroschisis in the National Birth Defects Prevention Study, 1997-2011.

BACKGROUND: Gastroschisis is particularly prevalent among offspring of young women and has increased over recent decades. Although previous studies suggest that maternal alcohol consumption is associated with increased gastroschisis risk, none have explored whether maternal age modifies that association. OBJECTIVE: The objective of the study was to evaluate associations between self-reported maternal periconceptional alcohol consumption (1 month prior through the third month after conception) and risk of gastroschisis among offspring, by maternal age. METHODS: We used data from the National Birth Defects Prevention Study (NBDPS), a multi-site population-based case-control study. The analysis included 1450 gastroschisis cases and 11,829 unaffected liveborn controls delivered during 1997-2011 in ten US states. We estimated adjusted odds ratios (aOR) and 95% confidence intervals (CI) for the individual and joint effects of alcohol consumption and young maternal age at delivery (<25 years vs ≥25 years) on gastroschisis risk. We estimated the relative excess risk due to interaction (RERI) to quantify additive interaction. RESULTS: Periconceptional alcohol consumption was common regardless of maternal age (women <25 years: cases 38.8%, controls 29.3%; women ≥25: cases 43.5%, controls 39.5%). Compared with women ≥25 years who did not consume alcohol, we observed increased risk of gastroschisis among women <25 years, with higher estimates among those who consumed alcohol (women <25 years who did not consume alcohol. aOR 5.90, 95% CI 4.89, 7.11; women <25 years who did consume alcohol: aOR 8.21, 95% CI 6.69, 10.07). Alcohol consumption among women ≥25 years was not associated with gastroschisis (aOR 1.12, 95% CI 0.88, 1.42). This suggests super-additive interaction between alcohol consumption and maternal age (RERI -2.19, 95% CI 1.02, 3.36). CONCLUSIONS: Periconceptional alcohol consumption may disproportionately increase risk of gastroschisis among young mothers. Our findings support public health recommendations to abstain from alcohol consumption during pregnancy.

Descriptive and risk factor analysis of nonsyndromic sacral agenesis: National Birth Defects Prevention Study, 1997-2011.

Sacral agenesis is a rare birth defect characterized by partial or complete absence of the sacrum. We sought to (a) describe case characteristics, (b) estimate birth prevalence, and (c) identify risk factors for nonsyndromic sacral agenesis using data from the National Birth Defects Prevention Study (NBDPS). The NBDPS was a population-based, case-control study involving pregnancies with estimated dates of delivery from October 1997 through December 2011. We estimated birth prevalence using all NBDPS eligible cases. Using self-reported maternal exposure information, we conducted multivariable logistic regression analysis to identify potential risk factors overall and among women without diabetes. The birth prevalence of sacral agenesis was 2.6/100,000 live births. In the multivariable analysis, multifetal pregnancy, pre-existing Type 1 diabetes, and pre-existing Type 2 diabetes were positively and significantly associated with sacral agenesis, albeit estimates were imprecise. Preexisting Type 1 diabetes was the strongest risk factor (adjusted odds ratio = 96.6, 95% confidence interval = 43.5-214.7). Among women without diabetes, periconceptional smoking was positively and significantly associated with sacral agenesis. Our findings underscore the importance of smoking cessation programs among women planning pregnancy and the importance of better understanding the role of glycemic control before and during pregnancy when designing interventions for primary prevention of sacral agenesis.

Fluconazole use and birth defects in the National Birth Defects Prevention Study.

BACKGROUND: Low-dose fluconazole is used commonly to treat vulvovaginal candidiasis, a condition occurring frequently during pregnancy. Conflicting information exists on the association between low-dose fluconazole use among pregnant women and the risk of major birth defects. OBJECTIVE: We used data from the National Birth Defects Prevention Study to examine this association. STUDY DESIGN: The National Birth Defects Prevention Study is a multisite, population-based, case-control study that includes pregnancies with estimated delivery dates from 1997 to 2011. Information on fluconazole use in early pregnancy was collected by self-report from 31,645 mothers of birth defect cases and 11,612 mothers of unaffected controls. Adjusted odds ratios and 95% confidence intervals were estimated for birth defects with 5 or more exposed cases; crude odds ratios and exact 95% confidence intervals were estimated for birth defects with 3-4 exposed cases. RESULTS: Of the 43,257 mothers analyzed, 44 case mothers and 6 control mothers reported using fluconazole. Six exposed infants had cleft lip with cleft palate, 4 had an atrial septal defect, and each of the following defects had 3 exposed cases: hypospadias, tetralogy of Fallot, d-transposition of the great arteries, and pulmonary valve stenosis. Fluconazole use was associated with cleft lip with cleft palate (odds ratio = 5.53; confidence interval = 1.68-18.24) and d-transposition of the great arteries (odds ratio = 7.56; confidence interval = 1.22-35.45). CONCLUSIONS: The associations between fluconazole and both cleft lip with cleft palate and d-transposition of the great arteries are consistent with earlier published case reports but not recent epidemiologic studies. Despite the larger sample size of the National Birth Defects Prevention Study, fluconazole use was rare. Further investigation is needed in large studies, with particular emphasis on oral clefts and conotruncal heart defects.

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.

Fever and antibiotic use in maternal urinary tract infections during pregnancy and risk of congenital heart defects: Findings from the National Birth Defects Prevention Study.

BACKGROUND: Previous studies report an association between prenatal maternal urinary tract infections (UTI) and specific congenital heart defects (CHDs); however, the role of fever and antibiotic use on this association is poorly understood. Using data from the National Birth Defects Prevention Study, we examined whether the relationship between maternal UTIs during the periconceptional period and occurrence of CHDs is modified by the presence of fever due to UTI and corresponding antibiotic use among 11,704 CHD case infants and 11,636 live-born control infants. METHODS: Information on UTIs, fever associated with UTI and antibiotic use (sulfonamides, nitrofurantoin, cephalosporins, penicillin, macrolides, and quinolones) during pregnancy were obtained using a computer-assisted telephone interview. Using unconditional multivariable logistic regression, we calculated adjusted odds ratios (ORs) to determine the association between maternal UTIs and subtypes of CHDs. Analyses were stratified by the presence of fever and medication use associated with UTI. RESULTS: The prevalence of UTIs during the periconceptional period was 7.6% in control mothers, and 8.7% in case mothers. In the absence of fever, UTI was associated with secundum atrial septal defects (ASD) (OR 1.3; 95% confidence interval [CI] 1.1-1.5) and in the absence of antibiotics, UTI was associated with conotruncal defects as a group and for four specific CHDs. When fever and UTI occurred concomitantly, no significantly elevated odds ratios were noticed for any subtypes of CHD. Among women with UTIs who used antibiotics, an elevated but statistically non-significant estimate was observed for secundum ASD (OR 1.4; 95% CI 1.0-2.0). CONCLUSION: Findings in the present study suggest that fever due to UTI and corresponding maternal antibiotic use do not substantially modify the association between maternal UTIs and specific CHDs in offspring. Further studies with larger sample sizes are warranted to guide clinical management of UTIs during the periconceptional period.

Antifungal medication use during early pregnancy and the risk of congenital heart defects in the National Birth Defects Prevention Study, 1997-2011.

BACKGROUND: Fungal infections are common among pregnant people. Recent studies suggest positive associations between oral antifungals used to treat fungal infections and congenital heart defects (CHDs). METHODS: We estimated associations between first trimester antifungal use and 20 major, specific CHDs using data from the National Birth Defects Prevention Study (NBDPS), a multi-site, case-control study that included pregnancies with estimated delivery dates from October 1997 through December 2011. Infants with CHDs ("cases") were ascertained from 10 birth defect surveillance programs. Live born infants without major birth defects ("controls") were randomly selected from birth records or hospital discharge lists. First trimester antifungal use was self-reported via maternal interview. We estimated adjusted odds ratios (AORs) and 95% confidence intervals (CIs) using logistic regression with Firth's penalized likelihood. RESULTS: First trimester antifungal use was reported by 148/11,653 (1.3%) case and 123/11,427 (1.1%) control participants. We estimated AORs for 12 CHDs; six had AORs >1.5 (tetralogy of Fallot, double outlet right ventricle with transposition of the great arteries [DORV-TGA], atrioventricular septal defect, hypoplastic left heart syndrome, pulmonary atresia, muscular ventricular septal defect), and one (pulmonary valve stenosis) had an AOR <0.7. All CIs included the null, except for DORV-TGA. CONCLUSIONS: First trimester antifungal use was rare. We observed some positive associations for several specific CHDs in our analysis, although the CIs largely included the null. Results do not support a large increase in risk, but smaller increases in risk for certain CHD cannot be ruled out.

A Comparison of Active and Passive Surveillance Strategies for Selected Birth Defects in New York.

BACKGROUND: The New York State Birth Defects Registry (BDR) has passive and active components. As part of statewide passive ascertainment, the BDR receives reports of International Classification of Diseases, Tenth Revision (ICD-10) codes and descriptive narratives on a wide range of birth defects. The BDR conducts enhanced active surveillance for selected birth defects in 14 counties, which includes medical record abstraction and clinician review. We sought to quantify agreement between the two surveillance approaches. METHODS: The analysis included live-born infants born with one of the 16 birth defects in 2018-2021 in the active surveillance counties (n = 1069 infants). We calculated positive predictive values (PPV) and 95% confidence intervals for each defect, defined as the percentage of cases confirmed in active surveillance among those in passive surveillance. Additionally, we calculated the percentage with each birth defect missed by passive surveillance. RESULTS: The PPV varied greatly by birth defect. The PPV was >90% for gastroschisis and cleft lip, but <70% for spina bifida, diaphragmatic hernia, truncus arteriosus, tricuspid atresia, hypoplastic left heart syndrome, coarctation of the aorta, and pulmonary atresia. The percentage missed by passive surveillance ranged from 2% for tetralogy of Fallot to 39% for tricuspid atresia. CONCLUSIONS: Active surveillance is an important strategy for ruling out false positive case reports for certain birth defects that we assessed, but not all of them. Passive surveillance programs can use our findings to develop targeted strategies for improving data quality of specific birth defects using active surveillance methods, thus optimizing limited resources.

Factors associated with infant sex and preterm birth status for selected birth defects from the National Birth Defects Prevention Study, 1997-2011.

BACKGROUND: Birth defects and preterm birth co-occur, with some overlapping risk factors. Many birth defects and preterm births tend to have a male preponderance. We explored potential risk factors impacting sex and preterm (<37 weeks of gestation) birth differences among infants with selected birth defects delivered from 1997 to 2011 using data from the National Birth Defects Prevention Study (NBDPS). METHODS: The NBDPS was a large multisite, population-based case-control study. Using random forests, we identified important predictors of male preterm, female preterm, and male term, each compared with female term births for each birth defect. Using logistic regression, we estimated odds ratios for associations between important predictors and sex-preterm birth status by birth defect. RESULTS: We examined 11,379 infants with nine specific birth defects. The top 10 most important predictors of sex-preterm birth status from the random forests varied greatly across the birth defects and sex-preterm comparisons within a given defect group, with several being novel factors. However, one consistency was that short interpregnancy interval was associated with sex-preterm birth status for many of the studied birth defects. Although obesity has been identified as a risk factor for preterm birth and birth defects in other research, it was not associated with sex-preterm birth status for any of the examined defects. CONCLUSIONS: We confirmed expected associations for sex-preterm birth status differences and found new potential risk factors for further exploration among the studied birth defects.

Risk of birth defects by pregestational type 1 or type 2 diabetes: National Birth Defects Prevention Study, 1997-2011.

BACKGROUND: Previous studies found consistent associations between pregestational diabetes and birth defects. Given the different biological mechanisms for type 1 (PGD1) and type 2 (PGD2) diabetes, we used National Birth Defects Prevention Study (NBDPS) data to estimate associations by diabetes type. METHODS: The NBDPS was a study of major birth defects that included pregnancies with estimated delivery dates from October 1997 to December 2011. We compared self-reported PGD1 and PGD2 for 29,024 birth defect cases and 10,898 live-born controls. For case groups with ≥5 exposed cases, we estimated adjusted odds ratios (aORs) and 95% confidence intervals (CIs) for the association between specific defects and each diabetes type. We calculated crude ORs (cORs) and 95% CIs with Firth's penalized likelihood for case groups with 3-4 exposed cases. RESULTS: Overall, 252 (0.9%) cases and 24 (0.2%) control mothers reported PGD1, and 357 (1.2%) cases and 34 (0.3%) control mothers reported PGD2. PGD1 was associated with 22/26 defects examined and PGD2 was associated with 29/39 defects examined. Adjusted ORs ranged from 1.6 to 70.4 for PGD1 and from 1.6 to 59.9 for PGD2. We observed the strongest aORs for sacral agenesis (PGD1: 70.4, 32.3-147; PGD2: 59.9, 25.4-135). For both PGD1 and PGD2, we observed elevated aORs in every body system we evaluated, including central nervous system, orofacial, eye, genitourinary, gastrointestinal, musculoskeletal, and cardiac defects. CONCLUSIONS: We observed positive associations between both PGD1 and PGD2 and birth defects across multiple body systems. Future studies should focus on the role of glycemic control in birth defect risk to inform prevention efforts.

Maternal exposure to heparin products and risk of birth defects in the National Birth Defects Prevention Study.

BACKGROUND: Heparin and low-molecular-weight heparin are the preferred anticoagulants during pregnancy as they do not cross the placenta. Although research on the safety of heparin products has been reassuring, previous studies have considered birth defects as a single outcome or by larger organ system and have not examined associations with specific birth defects. METHODS: We analyzed data from the National Birth Defects Prevention Study, a multisite, population-based case-control study from 1997 to 2011. We used unconditional logistic regression with Firth's penalized likelihood to calculate adjusted odds ratios (ORs) and profile likelihood 95% confidence intervals (CIs) for defects with at least five exposed cases. For defects with 3-4 exposed cases, we estimated crude ORs and exact 95% CIs. RESULTS: Of the 42,743 women in our analysis, 117 (0.4%) case and 44 (0.4%) control mothers reported using a heparin product in early pregnancy. The adjusted ORs ranged from 0.9 to 3.9 and were elevated for anorectal atresia (OR = 2.0, 95% CI = 0.8-4.3), longitudinal limb deficiency (3.5, 1.3-7.8), transverse limb deficiency (1.8, 0.6-4.3), atrioventricular septal defect (3.9, 1.4-9.0), and secundum atrial septal defect (2.2, 1.2-3.8). CONCLUSIONS: We observed elevated associations for some birth defects, although heparin is a rare exposure, which limited our ability to evaluate many associations. Future studies that can explore specific birth defects and adequately control for confounding by indication are needed. Given that women with an indication for heparin products during pregnancy often need to take medication, one must remain mindful of the underlying risk of a birth defect that exists regardless of medication use.

Agreement between maternal report and medical records on use of medications during early pregnancy in New York.

BACKGROUND: Studies evaluating associations between medication use in pregnancy and birth outcomes rely on various sources of exposure information. We sought to assess agreement between self-reported use of medications during early pregnancy and medication information in prenatal medical records to understand the reliability of each of these information sources. METHODS: We compared self-reported prescription medication use in early pregnancy to medical records from 184 New York women with deliveries in 2018 who participated in the Birth Defects Study To Evaluate Pregnancy exposureS. We assessed medications used chronically and episodically, and medications within 12 therapeutic groups. We calculated agreement using kappa (κ) coefficients, sensitivity, and specificity. We assessed differences by case/control status, maternal age, education, time to interview, and interview language. RESULTS: Medications used chronically showed substantial agreement between self-report and medical records (κ = 0.75, 0.61-0.88), with agreement for therapeutic groups used chronically ranging from κ = 0.61 for antidiabetics to κ = 1.00 for antihypertensives. Prescription medications used episodically showed worse agreement (κ = 0.40, 0.25-0.54), with the lowest agreement for opioid analgesics (κ = 0.20) and anti-infectives (κ = 0.33). Agreement did not differ by the characteristics examined, although we observed potential differences by interview language. CONCLUSIONS: Among our sample, we observed good agreement between self-report and medical records for medications used chronically and substantially less agreement for medications used episodically. Differences by source may be due to poor recall in self-reports, non-adherence with prescribed medications and lack of complete prescription information within medical records. Limitations should be considered when assessing prescription medication exposures during early pregnancy in epidemiologic studies.

Patterns of multiple congenital anomalies in the National Birth Defect Prevention Study: Challenges and insights.

BACKGROUND: About 20%-30% of children with birth defects have multiple major birth defects in more than one organ system, often referred to as multiple congenital anomalies (MCAs). Evaluating the patterns of MCAs can provide clues to the underlying causes, pathogenic mechanisms, and developmental pathways. We sought to explore selected patterns of MCAs within the National Birth Defects Prevention Study (NBDPS), a population-based, case-control study that excluded cases attributed to known chromosomal or single-gene abnormalities. METHODS: We defined MCAs as having two or more NBDPS-eligible birth defects and calculated the adjusted observed-to-expected ratio for all observed MCA patterns using co-occurring defect analysis. RESULTS: Of the 50,186 case infants eligible for NBDPS, 2,734 (3.7%) had at least two eligible birth defects. We observed 209 distinct 2-way combinations of birth defects, 297 distinct 3-way combinations, 179 distinct 4-way combinations, and 69 distinct 5-way combinations. Sacral agenesis had the largest proportion of cases with MCAs (70%), whereas gastroschisis had the lowest (3%). Among the cases with MCAs, 63% had a heart defect, 23% had an oral cleft, and 21% had anorectal atresia/stenosis. Of the patterns with adjusted observed-to-expected ratios in the top 20%, most were consistent with the known associations or syndromes, including VATER/VACTERL association and CHARGE syndrome. CONCLUSIONS: Most but not all patterns that had the highest adjusted observed-to-expected ratios were instances of known syndromes or associations. These findings highlight the importance of considering birth defect combinations that suggest syndromic patterns in the absence of a formal syndromic diagnosis. New approaches for screening for sequences and associations, and VATER/VACTERL in particular, in surveillance systems with limited resources for manual review may be valuable for improving surveillance system quality. The observed MCA patterns within NBDPS may help focus future genetic studies by generating case groups of higher yield.