SANTA BARBARA, CALIF. — Children of older mothers who drank during pregnancy were shorter and had smaller head circumferences at ages 7 and 14 years than other children at those ages, it was reported at the annual meeting of the Research Society on Alcoholism.
Children of mothers who were 30 or older at delivery were affected above a threshold of moderate alcohol consumption, defined as about one alcoholic drink a day at the time of conception.
Many women reduced their drinking during pregnancy, but the heaviest drinkers reduced their drinking less.
“Even if women reduce their drinking during pregnancy, their early drinking before they realize they are pregnant may have an impact on the infant,” said Sandra W. Jacobson, Ph.D., professor of psychiatry and behavioral neurosciences at Wayne State University in Detroit, a senior author on the study.
“We see effects in infants whose mothers drink as little as one drink/day.”
Dr. Jacobson stressed that “average” drinks per day did not reflect actual drinking patterns among women in the study. Just 1 woman of 480 in the Detroit Longitudinal Prenatal Alcohol Exposure study drank daily.
Many of the others concentrated their drinking on 1–2 days a week, in some cases drinking three to four drinks at each session, she explained following the meeting.
Mean alcohol consumption at conception was two drinks per day in the study of economically disadvantaged African American women and their children.
Mean alcohol intake dropped during pregnancy to a little more than two drinks per week.
Prenatal alcohol exposure was associated with lower birthweight and length in the entire sample of women, even after researchers controlled for smoking and other possible confounders.
For mothers over 30 at conception, the repercussions were long lasting. With a cutoff point of 0.5 ounces of alcohol per day at conception, older mothers' children were 1.2 cm, 3.1 cm, and 3.7 cm shorter at birth, 7.5 years, and 14 years, respectively, than children of mothers with minimal exposure.
Their mean head circumference was smaller by 4.6 mm, 7.3 mm, and 14.5 mm at birth, 7.5 years, and 14 years.
“Prenatal alcohol exposure was not related to weight or body mass index at 7.5 or 14 years, suggesting that the effects on height and head circumference were not attributable to poor maternal nutrition,” the researchers reported in their poster presentation.
Smoking during pregnancy resulted in lower birthweight and reduced length and head circumference at birth, but had no discernible impact on children's growth over time.
In contrast, prenatal alcohol exposure's impact on size was evident at birth and became magnified over time.
Although the study suggests that children of older mothers are most vulnerable to prenatal alcohol exposure, all women considering pregnancy should be urged to stop drinking or to cut down as much as possible. “At this time, no drinking is considered safe,” said Dr. Jacobson.
The study was supported by grants from the National Institute on Alcohol Abuse and Alcoholism and the Joseph Young, Sr., Fund of Michigan.
Douglas Fuller, a research assistant in the Wayne State University department of psychiatry and behavioral neurosciences, contributed to the study.