Drinking a little alcohol during pregnancy is just fine for most women, found a new study.
In fact, pregnant moms who are able to kick back and relax a little may even give their children a developmental leg up, at least for the first five years of life, which is how far the study tracked kids.
"Heavy binge drinking has been linked for a long time with difficulties for mothers and the children born to them," said lead researcher Yvonne Kelly, an epidemiologist at University College London.
"There hasn't been rigorous research to look at the lower end of the drinking spectrum," she added. "Regardless of the emotive issues, we wanted to look at the science."
The study, which found no evidence of harm from having a couple drinks a week during pregnancy, was so well done and its findings so conclusive that it ought to become the final word in the field, said Fred Bookstein, an applied statistician who studies fetal alcohol spectrum disorders at both the University of Washington, Seattle, and the University of Vienna.
"This is such a good study that it should shut down this line of research," said Boostein, who plans to refer people to the paper when they ask him about drinking during pregnancy, and hopes that research dollars can now go towards finding the effects of other, more troublesome chemicals.
"It is no longer valid to argue that we don't know enough about low-dose drinking during pregnancy or that the known effects of binge drinking may penetrate to low-dose drinkers somehow," he added. "There is no detectable risk associated with light or moderate drinking during pregnancy."
In the United Kingdom, where Kelly and colleagues work, mothers tend to have a relatively relaxed attitude toward alcohol during pregnancy. About a third of pregnant women report drinking at least some alcohol, Kelly said, offering a natural experiment to look at how levels of drinking affect children later on.
The researchers tapped into a long-term study that has followed more than 18,500 children since birth between 2000 and 2002.
When the babies were about 9 months old, moms were asked to describe how much alcohol they had consumed during pregnancy. Then, the babies took a series of tests that evaluated their behavioral, emotional and intellectual development. The kids took similar tests at age three and again at age five.
The scientist grouped the mothers by alcohol consumption. One group, called teetotalers, never drank, even when they weren't pregnant. Another group stopped during pregnancy but resumed drinking after having their babies. Light drinkers had no more than one or two drinks a week while pregnant. Moderate pregnant drinkers had up to 6 drinks per week or 5 drinks at once. Heavy binge drinkers consumed more than that.
A drink was defined as a small glass of wine, a half-pint of beer or a single serving of hard alcohol.
Final results of the study, published today in the Journal of Epidemiology and Community Health, agreed with previous work that children born to heavy binge drinkers do worst on developmental tests, because excessive exposure to alcohol in the womb kills nerve cells and causes brain damage.
The kids of teetotalers did almost as poorly, however, reflecting the complicated phenomenon that people who never drink have poor outcomes on many measures of health.
But the study found no evidence that light drinking during pregnancy causes emotional or learning problems in children through the age of five. In some tests of vocabulary and pattern creation, boys actually did best if their moms drank a little while carrying them. The findings confirmed what the researchers had found when the kids were three years old.
The results don't mean that alcohol is good for a developing fetus, Bookstein said. Rather, there's something about women who decide to cut down on alcohol while pregnant that also produces favorable results in their children, even if they don't cut out alcohol completely. They may be more medically informed, for example, which might also lead them to ask their doctors for advice, take vitamins and follow health news.
Drinking just a little could also help pregnant women relax, Kelly said. Plenty of recent studies have pointed out the risk of maternal stress to fetal development. A relaxed parenting style could be beneficial, too. But she stopped short of offering advice.
"It would be reckless to tell people to start doing something when there are all sorts of reasons why people wouldn't want to drink and shouldn't drink alcohol during pregnancy," she said. "At least the science is showing there isn't any increased risk of difficulties (with light drinking). That is the most sensible and cautious line."
Bookstein was more forthcoming. His group in Seattle, he said, has never seen a case of damage to a child whose mother drank during pregnancy, unless she binged. He defined a binge as five or more drinks in one sitting, four or more drinks several times a month, or drinking to the point of intoxication more than once.
"I tell my daughters not to worry about a drink a day, but don't ever get drunk and be aware that after the second drink, you're not going to be able to count," Bookstein said. "There's just no evidence that a drink a day is causing any damage."