Pattern and Timing of Prenatal Alcohol Exposure Is Associated with Specific Alcohol-Related Birth Defects and Growth Deficiencies
The association between pattern and timing of prenatal alcohol exposure and specific alcohol-related birth defects and growth deficiencies is uncertain. Researchers analyzed alcohol-consumption data from 992 pregnant women* enrolled between 1978–2005 in the California Teratogen Information Service and Clinical Research Program. Alcohol-consumption quantity and frequency were assessed every 3 months during pregnancy. Live-born singleton infants underwent examination by a dysmorphologist who was blinded to prenatal exposures.
- In the second half of the first trimester, each 1-drink increase in average drinks per day was associated with an increased risk of 25% for smooth philtrum, 22% for thin vermillion border, 12% for microcephaly, 16% for low birth weight, and 18% for reduced birth length. Higher risk was also seen with more heavy drinking episodes** and a higher maximum number of drinks per occasion.
- In the second trimester, higher average drinks per day and number of heavy drinking episodes were associated with greater risk for smooth philtrum and reduced birth weight and length, and higher maximum drinks per occasion was associated with increased risk for smooth philtrum and reduced birth length.
- In the third trimester, higher average drinks per day was associated with reduced birth length, and higher maximum drinks per occasion was associated with greater risk for smooth philtrum and reduced birth length.
- Models (not included in the paper) did not show a lower alcohol use threshold of no risk.
*Mean age, 31 years; 54% were white, and the mean gestational age at enrollment was 13 weeks.
**Heavy drinking episode = ≥4 drinks per occasion in this study.
Comments:This study indicates greater risk for alcohol-related birth defects and growth deficiencies across a range of prenatal alcohol use patterns in all 3 trimesters. Although the study did not assess the neurobehavioral effects of prenatal alcohol exposure, which are more common than alcohol-related birth defects, the public health message remains that women of child-bearing age should not drink alcohol during pregnancy or when trying to conceive. Kevin L. Kraemer, MD, MSc