Interaction between maternal smoking and malnutrition in infant risk of gastroschisis

BACKGROUND: Gastroschisis is a severe birth defect characterized by a tear in the infant's abdominal wall. Young mothers have the highest risk of having an infant with gastroschisis. In an animal model, the defect resulted from exposure of pregnant mice to carbon monoxide (CO) in combination with a low protein and low zinc diet. METHODS: We evaluated this model in a study of 55 infants with gastroschisis and 94 age-matched controls that included maternal interview with a food frequency questionnaire. Smoking cigarettes (> or = 1 pack/day) or marijuana (more than once) 3 months prior to pregnancy indicated CO exposure. Low protein or zinc intake and a low body mass index (BMI) indicated maternal malnutrition. RESULTS: When assessed separately, high CO, low protein, low zinc, and low BMI were each significantly associated with an increased risk of gastroschisis. Although we observed significant CO-BMI and CO-zinc interactions after adjusting for income, only a combination of high CO exposure and low BMI yielded a synergistic adverse effect. Compared to the low risk of having an infant with gastroschisis for mothers who did not have low BMI and did not smoke, the risk of having an infant with gastroschisis was 16.3 times (95% CI, 2.49-113.4) higher for mothers who did not have low BMI but smoked, and 19.7 times (95% CI, 4.33-89.6) higher for mothers who did not smoke but had low BMI. However, the risk was 26.5 times (95% CI, 7.85-89.4) higher for mothers who had low BMI and smoked. CONCLUSIONS: Our results suggest that young mothers are at increased risk of having an infant with gastroschisis if they smoke and are also malnourished.