For decades, women have been told that drinking any amount of alcohol during pregnancy can harm their developing child. The zero-alcohol rule is so ingrained that just walking into a bar while pregnant can draw suspicious stares.
But new data from Denmark suggests that light to moderate drinking early in pregnancy — up to eight drinks a week — has no effect on intelligence, attention or self-control in children at age 5. Drinking more heavily, however, was associated with measurable negative effects.
Researchers studied slightly more than 1,600 Danish women and their children, comparing those born to nondrinkers with children of heavy, light, moderate or binge drinkers. Women in the low-consumption group had one to four drinks a week; moderate drinkers had five to eight drinks a week; and heavy drinkers had nine or more. Binge drinking was defined as having at least five drinks on a single occasion. The research included nearly a third of all Danish women who were pregnant between 1997 and 2003.
In five papers published in the BJOG journal, the authors report finding no effect of light, moderate or even binge drinking in pregnancy on children’s overall IQ, ability to pay attention or executive function, which involves self-control and the ability to organize and plan behavior, at age 5.
However, children of heavy-drinking women who had nine or more drinks a week had reduced attention span and were nearly five times more likely to have low IQ than children of nondrinkers. Oddly, binge drinking during the first or second week of pregnancy was associated with a 54% lower risk of having a child with a low IQ, but the researchers think this finding occurred purely by chance and doesn’t show a true effect.
In all of the studies, the researchers controlled for other factors that can also affect a child’s brain development, such as maternal intelligence and smoking. The women in the study had an average age of 31, about half were having their first child and about 31% smoked.
“Our findings show that low to moderate drinking is not associated with adverse effects on the children aged 5. However, despite these findings, additional large scale studies should be undertaken to further investigate the possible effects,” the authors said in a statement.
Some previous studies have found negative effects from consumption of even the smallest amounts of alcohol during pregnancy, but other research has found no effect, and the problems discovered have been variable. Most recently, the data have been increasingly reassuring about light drinking during pregnancy: the Danish data are especially useful because, unlike in most prior research, the scientists questioned women about drinking while they were actually pregnant, rather than asking them to recall their drinking habits later. Since people’s memories can fade, inaccurate recall can skew such results.
It’s important to keep in mind, however, that the amount of alcohol in a standard drink varies from country to country. In the Danish study, a standard drink contained 12 g of pure alcohol, while in the U.S. a single drink contains 14 g; that’s the amount of alcohol found in a 12-oz. beer, 8 oz. of malt liquor, a 5-oz. glass of wine or a 1.5-oz. shot of hard liquor. In other words, Danish women who had one to eight drinks a week were consuming less alcohol overall than would American women at the same apparent level of drinking.
Another important consideration is genetics: there are large genetic variations in individuals’ ability to metabolize alcohol, and vulnerability to negative effects of prenatal drinking, including fetal alcohol spectrum disorders, is affected both by the mother’s genes and those of the child. Since the Danish study included only Danish-speaking women living in Denmark, the results could be very different for women of different backgrounds.
So, while everyone can raise a glass to salute these latest findings — and women who have had one or two during past pregnancies can let go of at least one source of guilt — experts continue to advise that abstinence is the safest option.
The occasional beer or glass of wine during pregnancy seems increasingly unlikely to do damage, but it’s worth remembering that fetal alcohol spectrum disorders are still the largest known cause of intellectual disability in children.