Association of Prenatal Exposure to Maternal Drinking and Smoking With the Risk of Stillbirth

This cohort study assesses whether prenatal exposure to alcohol, tobacco cigarettes, or both is associated with the risk of stillbirth in pregnant women from Cape Town, South Africa, and the Northern Plains region of the US. Question Is prenatal exposure to maternal drinking and smoking associated with the risk of stillbirth? Findings In this cohort study of 8506 pregnant women (with 11 892 pregnancies) in Cape Town, South Africa, and the Northern Plains in the US, dual exposure to drinking and smoking after the first trimester of pregnancy had 2.78 times the risk of late stillbirth compared with those with no exposure or who had quit before the end of the first trimester of pregnancy. Meaning These findings suggest that dual exposure to drinking and smoking after the first trimester of pregnancy is associated with nearly 3 times the risk of late stillbirth. IMPORTANCE Prenatal smoking is a known modifiable risk factor for stillbirth; however, the contribution of prenatal drinking or the combination of smoking and drinking is uncertain. OBJECTIVE To examine whether prenatal exposure to alcohol and tobacco cigarettes is associated with the risk of stillbirth. DESIGN, SETTING, AND PARTICIPANTS The Safe Passage Study was a longitudinal, prospective cohort study with data collection conducted between August 1, 2007, and January 31, 2015. Pregnant women from Cape Town, South Africa, and the Northern Plains region of the US were recruited and followed up throughout pregnancy. Data analysis was performed from November 1, 2018, to November 20, 2020. EXPOSURE Maternal consumption of alcohol and tobacco cigarettes in the prenatal period. MAIN OUTCOMES AND MEASURES The main outcomes were stillbirth, defined as fetal death at 20 or more weeks' gestation, and late stillbirth, defined as fetal death at 28 or more weeks' gestation. Self-reported alcohol and tobacco cigarette consumption was captured at the recruitment interview and up to 3 scheduled visits during pregnancy. Participants were followed up during pregnancy to obtain delivery outcome. RESULTS Of 11663 pregnancies (mean [SD] gestational age at enrollment, 18.6 [6.6] weeks) in 8506 women for whom the pregnancy outcome was known by 20 weeks' gestation or later and who did not terminate their pregnancies, there were 145 stillbirths (12.4 per 1000 pregnancies) and 82 late stillbirths (7.1 per 1000 pregnancies). A total of 59% of pregnancies were in women from South Africa, 59% were in multiracial women, 23% were