Change in prepregnancy body mass index and gastroschisis

Maternal body mass index (BMI) is inversely associated with gastroschisis, but a causal relationship has not been established. As data demonstrating that a change in exposure status is related to a change in the frequency of the outcome can add to the evidence for causality, we conducted a case–control study of change in maternal BMI, assessed using interpregnancy change in BMI (IPC-BMI), and gastroschisis. Data for 258 gastroschisis cases and 2561 controls were obtained from the Texas Birth Defects Registry and vital records (2006–2012). Logistic regression was used to estimate the adjusted association between IPC-BMI and gastroschisis. The continuous IPC-BMI variable was inversely associated with gastroschisis (adjusted odds ratio [aOR] = 0.90, 95% confidence interval [CI]: 0.86, 0.95). When assessed as a six-level categorical variable, with weight stable women as the referent, the odds of gastroschisis were higher following a BMI decrease of greater than 1 unit (aOR = 1.37, 95% CI: 0.91, 2.06) and lower after a BMI increase of ≥3 units (aOR = 0.62, 95% CI: 0.42, 0.94). Our findings suggest that maternal change in BMI is associated with gastroschisis and, thus, add to the epidemiological evidence that can be used to inform our understanding of the relationship between BMI and gastroschisis.