Low alcohol consumption and pregnancy and childhood outcomes: time to change guidelines indicating apparently ‘safe’ levels of alcohol during pregnancy? A systematic review and meta-analyses

Objectives: To determine the effects of low-to-moderate levels of maternal alcohol consumption in pregnancy on pregnancy and longer-term offspring outcomes.

Search Strategy: Medline, Embase, Web of Science, and Psychinfo from inception to 11-07-2016.

Selection Criteria: Prospective observational studies, negative control and quasi-experimental studies of pregnant women estimating effects of light drinking in pregnancy (≤32g/week) versus abstaining. Pregnancy outcomes such as birth weight, and features of fetal alcohol syndrome were examined.

Data Collection and Analysis: One reviewer extracted data and another checked extracted data. Random effects meta-analyses were performed where applicable, and a narrative summary of findings was carried out otherwise.

Main Results: 24 cohort and two quasi-experimental studies were included. With the exception of birth size and gestational age, there was insufficient data to meta-analyse or make robust conclusions. Odds of small-for-gestational-age (SGA) and preterm birth were higher for babies whose mothers consumed up to 32g/week versus none, but estimates for preterm birth were also compatible with no association: summary odd ratios (OR) 1·08, 95% confidence intervals (CI) (1·02 to 1·14), I2 0%, (7 studies, all estimates were adjusted) OR 1·10, 95%CI (0·95 to1·28), I2 60%, (9 studies, includes one unadjusted estimates) respectively. The earliest time points of exposure were used in the analysis.

Conclusion: Evidence of the effects of drinking <=32g/w in pregnancy is sparse. As there was some evidence that even light prenatal alcohol consumption is associated with being SGA and preterm delivery, guidance could advise abstention as a precautionary principle, but should explain the paucity of evidence.