NEIGHBORHOOD-LEVEL SOCIOECONOMIC POSITION DURING EARLY PREGNANCY AND THE RISK OF GASTROSCHISIS

Background: Studies have shown that pregnant women in low socioeconomic neighborhoods are at a higher risk of adverse pregnancy outcomes, including birth defects. However, few studies have explored this association with gastroschisis. Using data from the National Birth Defects Prevention Study (NBDPS), we investigated the association between neighborhood-level socioeconomic position (nSEP) during early pregnancy and the risk of gastroschisis, and evaluated whether nSEP modifies the associations between maternal age at conception and pre-pregnancy body mass index (BMI) and gastroschisis. Methods: We analyzed data from singleton case infants diagnosed with gastroschisis and singleton non-malformed control infants delivered between 1997 and 2011. To characterize nSEP, two principal component analysis (PCA)-derived indices were constructed including the Neighborhood Deprivation Index (NDI) and a Neighborhood-level Socioeconomic Position Index (nSEPI). Maternal neighborhood was defined as the self-reported address mothers lived at the longest between one month prior to conception to the third month of pregnancy. Generalized estimating equations were used to estimate odds ratios (ORs) and 95% confidence intervals (95% CIs), and relative excess risks due to interaction (RERI) were calculated to assess modification by nSEP on the additive scale. Results: Mothers in moderate (NDI aOR: 1.25; 95% CI: 1.05, 1.49 and nSEPI aOR: 1.25; 95% CI: 1.04, 1.49) or low SEP neighborhoods (NDI aOR; 1.27; 95% CI: 1.05 1.54 and nSEPI aOR: 1.32, 95% CI: 1.09, 1.61) were more likely to deliver an infant with gastroschisis compared with mothers in high SEP neighborhoods. Residing in low SEP neighborhoods sub-additively modified the association between maternal age at conception and gastroschisis. Young mothers (< 20 years) in high SEP neighborhoods had double the risk of having an infant with gastroschisis (aOR: 6.55; 95% CI: 4.59, 9.35) compared with young mothers in low SEP neighborhoods (aOR: 3.13, 95% CI: 2.59, 3.78). However, nSEP did not modify the association between pre-pregnancy BMI and gastroschisis. Regardless of nSEP, young maternal age at conception and normal or underweight BMI were consistently associated with elevated odds of gastroschisis. Conclusions: Future studies of nSEP should consider examining potential mechanisms through which contextual factors may influence individual-level characteristics and/or its association with gastroschisis.Doctor of Philosoph