Although the alcohol-exposed babies' growth remained within normal range, the findings reveal effects of drinking on the developing human brain. The study will appear in the May issue of Alcoholism: Clinical and Experimental Research.
"What this tells us is that the earlier you abstain in a pregnancy, the better the outcome," said lead author Nancy Handmaker, a University of New Mexico clinical psychologist with expertise in maternal-fetal health.
Alcohol use during pregnancy is a leading preventable cause of birth defects and developmental disabilities in the United States, according to the Centers for Disease Control and Prevention. Fetal Alcohol Spectrum Disorder -- which includes a range of cognitive, emotional and behavioral problems -- may be present in as many as one of every 100 births.
The study authors obtained routine ultrasound data from 167 pregnant women who had reported a history of hazardous drinking before pregnancy. Of these, 97 were classified as heavy drinkers. The study compared the fetal growth measures among drinkers who quit after learning of their impending motherhood to those among women who continued to drink.
Within the heavy drinking group, the ultrasounds revealed that fetuses of the continuing drinkers had a smaller ratio of head-to-abdominal circumference, which indicates reduced skull growth. They also had smaller measures of the cerebellum, a region of the brain involved in many mental, motor and sensory tasks.
Fetal growth measures were essentially the same among nondrinkers and those who quit when they learned of their pregnancy. "There may have been measures that were not part of routine ultrasound examinations that would have been more sensitive to the pr e-recognition drinking," said Handmaker.
The authors say that while women's own reports of their drinking habits may not be entirely accurate, the study findings are consistent with other research on fetal alcohol exposure in animals and humans.
"The provision of feedback on fetal development as revealed in ultrasonography may be a strategy to encourage heavy drinkers to seek treatment during pregnancy," concludes the study.
CDC would like to see intervention efforts start even earlier. "The best opportunity to identify and intervene with women at high-risk for an alcohol-exposed pregnancy is prior to pregnancy," says Louise Floyd of the Fetal Alcohol Prevention Team. "What we are hoping to see is a major shift in looking at a healthy pregnancy as something that we start to support in the preconception period."