Two Drinks Too Many

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 Science.

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.

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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.

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