A study explored the association between alcohol consumption, before and during pregnancy, and the risk of preterm birth among 46,252 mothers.
Information on alcohol consumption from questionnaire responses at pregnancy week 15 was obtained from the prospective, observational Norwegian Mother and Child Cohort Study. Data on preterm birth, categorised as delivery before gestation week 37, were retrieved from the Medical Birth Registry of Norway.
Among the participants, 91% consumed alcohol before pregnancy and fewer than 20% reported consuming alcohol during pregnancy. The adjusted odds ratio (aOR) for preterm birth associated with prepregnancy alcohol consumption was 0.81 (95% confidence interval [CI], 0.70-0.95). The researchers did not find a risk reduction for overall drinking during pregnancy, aOR = 1.03 (95% CI, 0.90-1.19). However, dose-response analyses showed tendencies toward adverse effects when drinking 1-3 times per month during the first 15 weeks of pregnancy, aOR = 1.51 (95% CI, 1.14-2.00).
The authors conclude that there were no effects on preterm birth from alcohol consumption during pregnancy, whereas pre-pregnancy drinking was associated with reduced risk of preterm birth. Residual confounding may have influenced the risk estimates, especially before pregnancy, as nondrinkers have lower socioeconomic status and well-being than drinkers they comment.
Source: Alcohol consumption among first-time mothers and the risk of preterm birth: a cohort study. Dale MT; Bakketeig LS; Magnus P. Annals of Epidemiology Published early online 29 September 2015