Are individual-level risk factors for gastroschisis modified by neighborhood-level socioeconomic factors?

BACKGROUND: Two strong risk factors for gastroschisis are young maternal age (<20 years) and low/normal pre-pregnancy body mass index (BMI), yet the reasons remain unknown. We explored whether neighborhood-level socioeconomic position (nSEP) during pregnancy modified these associations. METHODS: We analyzed data from 1269 gastroschisis cases and 10,217 controls in the National Birth Defects Prevention Study (1997-2011). To characterize nSEP, we applied the neighborhood deprivation index and used generalized estimating equations to calculate odds ratios and relative excess risk due to interaction. RESULTS: Elevated odds of gastroschisis were consistently associated with young maternal age and low/normal BMI, regardless of nSEP. High-deprivation neighborhoods modified the association with young maternal age. Infants of young mothers in high-deprivation areas had lower odds of gastroschisis (adjusted odds ratio [aOR]: 3.1, 95% confidence interval [CI]: 2.6, 3.8) than young mothers in low-deprivation areas (aOR: 6.6; 95% CI: 4.6, 9.4). Mothers of low/normal BMI had approximately twice the odds of having an infant with gastroschisis compared to mothers with overweight/obese BMI, regardless of nSEP (aOR range: 1.5-2.3). CONCLUSION: Our findings suggest nSEP modified the association between gastroschisis and maternal age, but not BMI. Further research could clarify whether the modification is due to unidentified biologic and/or non-biologic factors.

Neighborhood-level Socioeconomic Position During Early Pregnancy and Risk of Gastroschisis.

BACKGROUND: Neighborhood-level socioeconomic position has been shown to influence birth outcomes, including selected birth defects. This study examines the un derstudied association between neighborhood-level socioeconomic position during early pregnancy and the risk of gastroschisis, an abdominal birth defect of increasing prevalence. METHODS: We conducted a case-control study of 1,269 gastroschisis cases and 10,217 controls using data from the National Birth Defects Prevention Study (1997-2011). To characterize neighborhood-level socioeconomic position, we conducted a principal component analysis to construct two indices-Neighborhood Deprivation Index (NDI) and Neighborhood Socioeconomic Position Index (nSEPI). We created neighborhood-level indices using census socioeconomic indicators corresponding to census tracts associated with addresses where mothers lived the longest during the periconceptional period. We used generalized estimating equations to estimate odds ratios (ORs) and 95% confidence intervals (CIs), with multiple imputations for missing data and adjustment for maternal race-ethnicity, household income, education, birth year, and duration of residence. RESULTS: Mothers residing in moderate (NDI Tertile 2 aOR = 1.23; 95% CI = 1.03, 1.48 and nSEPI Tertile 2 aOR = 1.24; 95% CI = 1.04, 1.49) or low socioeconomic neighborhoods (NDI Tertile 3 aOR = 1.28; 95% CI = 1.05, 1.55 and nSEPI Tertile 3 aOR = 1.32, 95% CI = 1.09, 1.61) were more likely to deliver an infant with gastroschisis compared with mothers residing in high socioeconomic neighborhoods. CONCLUSIONS: Our findings suggest that lower neighborhood-level socioeconomic position during early pregnancy is associated with elevated odds of gastroschisis. Additional epidemiologic studies may aid in confirming this finding and evaluating potential mechanisms linking neighborhood-level socioeconomic factors and gastroschisis.

Assessing associations between residential proximity to greenspace and birth defects in the National Birth Defects Prevention Study.

BACKGROUND: Residential proximity to greenspace is associated with various health outcomes. OBJECTIVES: We estimated associations between maternal residential proximity to greenspace (based on an index of vegetation) and selected structural birth defects, including effect modification by neighborhood-level factors. METHODS: Data were from the National Birth Defects Prevention Study (1997-2011) and included 19,065 infants with at least one eligible birth defect (cases) and 8925 without birth defects (controls) from eight Centers throughout the United States. Maternal participants reported their addresses throughout pregnancy. Each address was systematically geocoded and residences around conception were linked to greenspace, US Census, and US Department of Agriculture data. Greenspace was estimated using the normalized difference vegetation index (NDVI); average maximum NDVI was estimated within 100 m and 500 m concentric buffers surrounding geocoded addresses to estimate residential NDVI. We used logistic regression to estimate odds ratios (ORs) and 95% confidence intervals comparing those in the highest and lowest quartiles of residential NDVI and stratifying by rural/urban residence and neighborhood median income. RESULTS: After multivariable adjustment, for the 500 m buffer, inverse associations were observed for tetralogy of Fallot, secundum atrial septal defects, anencephaly, anotia/microtia, cleft lip ± cleft palate, transverse limb deficiency, and omphalocele, (aORs: 0.54-0.86). Results were similar for 100 m buffer analyses and similar patterns were observed for other defects, though results were not significant. Significant heterogeneity was observed after stratification by rural/urban for hypoplastic left heart, coarctation of the aorta, and cleft palate, with inverse associations only among participants residing in rural areas. Stratification by median income showed heterogeneity for atrioventricular and secundum atrial septal defects, anencephaly, and anorectal atresia, with inverse associations only among participants residing in a high-income neighborhood (aORs: 0.45-0.81). DISCUSSION: Our results suggest that perinatal residential proximity to more greenspace may contribute to a reduced risk of certain birth defects, especially among those living in rural or high-income neighborhoods.

Using a Birth Defects Surveillance Program to Enhance Existing Surveillance of Stillbirth.

Objective: Fetal death certificates (FDCs) are the main source of stillbirth surveillance data in the United States, yet previous studies suggest FDCs have incomplete ascertainment. The objectives of this analysis were (1) to evaluate whether the use of an existing birth defects surveillance program (the Metropolitan Atlanta Congenital Defects Program [MACDP]) to conduct surveillance on stillbirths enhances case ascertainment, and (2) to compare stillbirth prevalence estimates in metropolitan Atlanta using data from MACDP and FDCs, independently and combined, from 2009-2015. Methods: Stillbirths were ascertained by MACDP and FDCs from 2009-2015. Capture-recapture methods were used to estimate the relative contributions of each data source. Prevalence estimates generated from each data source independently and combined were compared. Results: There were 3,031 stillbirths ascertained by FDCs and MACDP in metropolitan Atlanta from 2009-2015. It was assumed that 35% of FDCs unlinked to MACDP were misclassified as stillbirth. Under this assumption, an estimated 2,610 total stillbirths occurred. Accounting for potential misclassification in the FDC, the prevalence rate for stillbirth was 6.9 per 1,000 live births plus stillbirths for stillbirths captured only in FDC, and 6.2 per 1,000 live births plus stillbirths for stillbirths caught only in MACDP. Using both sources combined for casefinding, the prevalence rate was 10.0 per 1,000 live births plus stillbirths for all years combined. Conclusions: Expanding certain birth defects surveillance programs to conduct surveillance on stillbirths could potentially enhance existing surveillance data on stillbirths when linked to FDCs.