On Alcohol and Pregnancy, the Jury’s Still Out

Two new studies take up the question of alcohol consumption during pregnancy. While their objectives were dissimilar and their results don't conflict, they illustrate the murky nature of information available to women on the controversial subject.

In one paper, published in the journal Pediatrics, researchers found that as many as 4.8 percent of children in a sample population in the Midwest likely suffer from fetal alcohol spectrum disorders (FASD)—an alarmingly high prevalence. However, another recent study from Yale University, surveying women in Massachusetts and Connecticut, showed that light to moderate alcohol consumption during the earliest and latest stages of pregnancy had no association with negative health outcomes.

The Midwest study was looking for cases of FASD, typically the result of heavy alcohol exposure during pregnancy; the New England study focused on much lower levels of alcohol consumption. Conventional wisdom has held that binge drinking is detrimental during pregnancy while light drinking is permissible; these experiments could bring health professionals closer to determining a threshold for safe drinking while expecting.

In the first study, researchers found a town in the Midwestern United States deemed to be demographically representative of the country at large. A pediatric dysmorphologist—a doctor trained to diagnose disorders based on congenital malformations, in this case FASD based on facial characteristics—examined a population of first-graders enrolled in the town’s schools, also measuring the children’s cognition and behavior and polling subjects’ mothers on their drinking habits during pregnancy. The objective was to determine, based on symptoms and confirmed by mothers’ drinking reports, whether more children might suffer from FASD than are presently diagnosed.

“Probably 90 percent of the kids we diagnose in studies like this have never even been sent in for a diagnosis of FASD,” said Dr. Philip May, of the Gillings School of Global Public Health at the University of North Carolina at Chapel Hill and an author of the study. Yet even in mild cases, May told Wine Spectator, FASD may cause serious developmental and cognitive limitations. “What happens in the mild end is that the kids are born fairly normal-looking and have IQs which are in the normal range," May said. "However, when you do specific batteries of tests, you find that they have some of these other deficits that can be attributed to alcohol,” including poor working memory, inability to focus and lack of problem-solving skills.

Based on the population studied, May and his colleagues estimate that while acute fetal alcohol syndrome (FAS) likely affected less than 0.01 percent of children, the range of FASD conditions probably affected between 2.4 and 4.8 percent. The damage, claims study author Dr. Eugene Hoyme, of Sanford School of Medicine of the University of South Dakota, is often inflicted before a woman realizes that she's pregnant. “Our message is that alcohol is probably the most dangerous environmental agent that women can be exposed to in early pregnancy, certainly more dangerous than cigarette smoking or most other illicit drugs,” Hoyme said.

The Yale scientists present a different perspective. They analyzed data from a cohort of about 4,500 pregnant women in Massachusetts and Connecticut who reported, in detail, alcohol intake in their first and third trimesters. Three primary dimensions were measured: preterm delivery, low birth weight and intrauterine growth restriction. The result? “We did not find an increased risk [for the three primary birth outcomes examined],” said Dr. Lisbet Lundsberg, an associate research scientist at the Yale School of Medicine and an author of the study.

In fact, for some negative outcomes, including low birth weight, light to moderate drinkers actually appeared to show a reduced risk compared with nondrinkers, though these associations were not statistically significant when lifestyle variables were taken into account. Still, Lundsberg said, some patterns of drinking showed a significant reduced effect, and further exploration of factors—including the role of a healthy lifestyle among pregnant women who consume lower levels of alcohol—would be important. The study did not evaluate neurodevelopmental or long-term outcomes in the offspring, including FAS and FASD.

While her study showed a high prevalence of drinking, Lundsberg pointed out that, in general, the volumes consumed were quite low. “About 30 percent of women reported some exposure to alcohol in the first month of pregnancy,” she explained, but the median exposure was the equivalent of about one drink per week.

Many questions remain: Could prenatal nutrition influence alcohol's effect on development? Does the type of alcohol consumed make a difference? But Lundsberg believes that studies like hers may lead health professionals to better understand the possible effects of light to moderate drinking during pregnancy.