Drinking alcohol and smoking tobacco cigarettes throughout the first trimester of pregnancy is associated with nearly three times the risk of late stillbirth (at 28 or more weeks), compared to women who neither drink or smoke during pregnancy or quit both before the end of the first trimester, according to a study funded by the National Institutes of Health. Although prenatal smoking is known to increase stillbirth risk, the researchers conducted the study to examine how smoking combined with alcohol use might influence the risk. The researchers also confirmed the higher stillbirth risk from alcohol alone, which has been suggested by earlier, less comprehensive studies.

The study was conducted by researchers in the Prenatal Alcohol in SIDS and Stillbirth (PASS) Network and appears in JAMA Network Open. Funding was provided by NIH's Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institute on Alcohol Abuse and Alcoholism (NIAAA), and National Institute on Deafness and Other Communication Disorders (NIDCD).

The study followed nearly 12,000 pregnancies among more than 8,500 women in South Africa and the U.S. Northern Plains. Compared to the pregnancies of women who did not drink or smoke or who quit both before the second trimester, women who drank and smoked through the first trimester and beyond had 2.78 times the risk for late stillbirth. Previously, the PASS Network found that the risk of Sudden Infant Death Syndrome, or SIDS, was 12 times higher in pregnancies exposed to maternal drinking and smoking past the first trimester.

NIAAA warns against drinking any alcohol during pregnancy because it can result in birth defects and neurodevelopmental abnormalities. The U.S. Centers for Disease Control and Prevention notes that smoking during pregnancy increases the risk for pregnancy complications, preterm birth, sudden infant death syndrome and infant health problems.