Two Drinks Too Many

Contrary to popular belief, alcohol does the most damage during the second half of a pregnancy.

By Richard Lovett, published on May 1, 2004 - last reviewed on June 9, 2016

It happens every day: a woman discovers she's pregnant, then
remembers with dread the cocktails she consumed the week before.
According to a new study, she can probably breathe easy, but she should
focus most of her caution on the second half of pregnancy, when alcohol
does the most damage.

John W. Olney, a neuropsychopharmacologist from Washington
University in St. Louis, found that alcohol accelerates a natural process
called neuroapoptosis, which causes developing neurons to "commit
suicide" if they fail to connect on schedule with neighboring brain
cells. Alcohol slows the rate at which connections are formed, fooling
cells into believing they've failed to make contact. Olney reported his
findings at a meeting of the American Association for the Advancement of

Working with mice, Olney found that as little as one hour's
exposure to blood alcohol levels of 0.06 to 0.08 percent—just below the
legal driving limit in most states—substantially increases the death rate
of developing brain cells. Humans, most likely, would be similarly
affected. "Over the millennia, alcohol has damaged more fetal brains than
any other agent in the human environment," Olney says.

It's a common misconception that the crucial period for brain
development is during the first few months of pregnancy. Some women
report "cheating" in late pregnancy by having an occasional drink; Olney
believes it's best for pregnant women to shun alcohol, but he doubts that
one glass of wine poses a problem. "But if one glass leads to another and
then another on the same day, that is a different matter," he says.
"Then, blood alcohol levels remain above the toxic threshold for too
long, and nerve cells commit mass suicide."

Olney's research contrasts with a human study presented at the same
meeting that calls into question whether any alcohol consumption during
pregnancy is safe. The 25-year study of babies born to mothers who were
social drinkers found that even moderate levels of alcohol consumption
had measurable effects on the babies. Ann Streissguth, architect of the
study and director of the Fetal Alcohol Unit at the University of
Washington School of Medicine in Seattle, found the effects were
strongest in the children of the heaviest drinkers. The study also
concluded that no minimum level of drinking was safe.