Association between maternal alcohol consumption during pregnancy and risk of preterm delivery: the Japan Environment and Children's Study

OBJECTIVE: To examine the association between maternal alcohol consumption during pregnancy and the risk of preterm delivery. DESIGN: Prospective cohort study. SETTING: The Japan Environment and Children's Study (JECS). POPULATION: A total of 94 349 singleton pregnancies. METHODS: Participants completed questionnaires detailing alcohol consumption during the first trimester and during the second and third trimesters. Participants were divided into four categories according to alcohol consumption (non‐drinkers, consumers of 1–149 g, 150–299 g and ≥300 g ethanol/week). We examined the effect of alcohol consumption during different stages of pregnancy on the risk of preterm delivery. Odds ratios (OR) and 95% CI were calculated relative to non‐drinkers using logistic regression. MAIN OUTCOME MEASURES: Medical record‐based preterm delivery. RESULTS: Alcohol consumption during the second and third trimesters, but not during the first trimester, was associated with increased risk of preterm delivery. Heavy alcohol consumption (≥300 g ethanol/week) during the second and third trimesters was associated with a four‐fold higher risk compared with non‐drinkers (multivariable OR 4.52; 95% CI 1.68–12.2). Light alcohol consumption (1–149 g ethanol/week) tended to be associated with lower risk of preterm delivery (multivariable OR 0.78; 95% CI 0.60–1.00). CONCLUSIONS: Heavy alcohol consumption during the second and third trimesters was associated with increased risk of preterm delivery among pregnant women. TWEETABLE ABSTRACT: Heavy drinking during pregnancy may increase the risk of preterm delivery.