Prenatal Alcohol Exposure and Risk of Birth Defects

To investigate the association between prenatal alcohol use and birth defects, researchers in Australia studied maternal alcohol consumption in a population-based cohort of 4714 women (singleton births only). Alcohol use was classified as none (abstinence throughout pregnancy), low (<7 drinks* per week and no more than 2 drinks in a day), moderate (≤7 drinks per week but >2 standard drinks per occasion, including consumption of ≥5 drinks per occasion less than weekly), and heavy (≥5 drinks per occasion 1 or more times per week or >7 drinks per week). Consumption was assessed for the 3-month period prepregnancy, for the first trimester, and for late pregnancy (second and third trimesters). Information regarding birth defects was obtained through the Western Australia Birth Defects Registry and grouped into 2 categories: any birth defect and alcohol-related birth defects (ARBDs) as defined by the US Institute of Medicine.

• Forty-one percent of women abstained throughout pregnancy. Twenty-eight percent reported low consumption, 11% reported moderate consumption, and 3.7% reported heavy consumption during the first trimester. Thirty-eight percent reported low consumption, 11% reported moderate consumption, and 2% reported heavy consumption during late pregnancy.

• Fifty-one children (1.1%) with at least 1 ARBD were identified; of these, 4 had 2 birth defects.

• In analyses adjusted for maternal age, marital status, parity, income, smoking, and drug use during pregnancy, compared with women who abstained, women who drank heavily in the first trimester had higher odds of giving birth to infants with an ARBD (odds ratio [OR], 4.57).

• There was no significant association between low, moderate, or heavy alcohol consumption in late pregnancy and any birth defects, including ARBDs.

Comments:

In this study, the prevalence of birth defects was low (although only defects evident shortly after birth were studied), and no evidence was found for an association between low or moderate drinking and ARBDs. These results add to the evidence that heavy drinking in early pregnancy is associated with the occurrence of ARBDs. As such, it is important to provide information on the effects of heavy alcohol use on the fetus to women of childbearing age, stressing that, although safe drinking levels during pregnancy are unknown, alcohol exposure is one of the preventable causes of birth defects.

Nicolas Bertholet, MD, MSc

Reference:

O’Leary CM, Nassar N, Kurinczuk JJ, et al. Prenatal alcohol exposure and risk of birth defects. Pediatrics. 2010;126(4):e843–e850.