Study: Alcohol Consumption Riskiest Late in the First Trimester

A new study published in the journal Alcoholism: Clinical and Experimental Research reveals that during the second half of the first trimester, every one drink per day increase in alcohol intake raises the odds of certain physical abnormalities associated with fetal alcohol syndrome. Babies are 25 percent more likely to have abnormally-shaped lips, 12 percent more likely to have a smaller than normal head, and 16 percent more likely to have a low birth weight.

In contrast, a similar number of drinks during the third trimester seems to primarily affect birth weight.


To conduct the study, Dr. Christina Chambers of the University of California San Diego and her research team recruited 992 pregnant women who called a California help line that answers questions on substances that could be harmful during pregnancy. The callers — phoning in between 1978 and 2009 — were asked to participate in a follow-up study where they were asked about their alcohol consumption throughout their pregnancy and their infants were screened with a full physical exam.

Doctors examining the babies did not know whether the child had been exposed to alcohol or other chemical substances in utero. The researchers found that higher alcohol consumption during pregnancy was linked to a greater chance of the baby showing characteristics of fetal alcohol syndrome, including abnormal head size and altered shape of the eyes and the lips. Many also showed the presence of related neurological problems.

Researchers concluded that different mothers have different risks, because of other influences including diet, body fat levels, genetic differences, and environmental exposures. Future studies are anticipated that will look at both physical abnormalities as well as the neurological effects of alcohol on the fetus.