Effects of Alcohol Consumption During Pregnancy on Preterm Birth

While drinking alcohol during pregnancy can cause teratogenic effects, its relationship to preterm delivery, a main cause of neonatal morbidity and mortality, is unclear. To examine this relationship, researchers assessed 40,892 women in the Danish National Birth Cohort (a study of pregnant women and offspring) who completed a computer-assisted telephone interview while pregnant and gave birth to a liveborn singleton.

Of the births, 1880 were preterm (<37 weeks gestation). In analyses adjusted for risk factors for preterm birth, women who drank

• 2–3.5 drinks per week during pregnancy significantly lowered their risk of preterm birth (relative risk 0.8) compared with abstainers;
• 1.5 or fewer drinks per week lowered risk (e.g., RR 0.9 for 0.5 drinks per week), but not significantly;
• 4 or more drinks per week increased risk (e.g., RR 1.8 for 7 or more drinks per week), but not significantly;
• 1 or more drinks per week increased risk of very preterm birth (<32 weeks gestation) (e.g., RR 3.3 for 7 or more drinks per week), but not significantly.

Type of alcoholic beverage was not associated with preterm birth.

Comments:

While the increases in preterm birth associated with consuming 4 or more drinks per week were not statistically significant, they are consistent with findings from some previous studies. Because of the many adverse outcomes of heavy alcohol consumption—as well as an undetermined “safe” amount—during pregnancy, advising pregnant women to abstain remains the safest approach. However, patients who have an occasional drink during pregnancy may not be increasing their risk of preterm birth.

R. Curtis Ellison, MD

Reference:

Albertsen K, Andersen AN, Olsen J, et al. Alcohol consumption during pregnancy and the risk of preterm delivery. Am J Epidemiol. 2004;159(2):155–161.
(view abstract)