Having one to two drinks a week during pregnancy may not actually harm a developing fetus, new research suggests.

Researchers following children up to the age of 5 did not see any increased risk of behavioral or cognitive problems in those whose mothers classified themselves as "light drinkers" compared to mothers who were teetotalers during their pregnancy.

However, although the findings may be "reassuring for those who have taken a few drinks during early pregnancy, I would not use this as a green light to drink during pregnancy," cautioned Dr. Richard Jones, an assistant professor of obstetrics and gynecology at Texas A&M Health Science Center College of Medicine and director of obstetrics at Scott & White in Temple. "We know that heavy drinking causes problems in pregnancy."

"The March of Dimes has not changed its recommendations of no alcohol during pregnancy, and my personal view is absolutely consonant with that," added Dr. Michael Katz, senior vice president for research and global programs at the March of Dimes Foundation. "I can only see ill consequences as the result of (drinking alcohol during pregnancy). There are no precise measures (of alcohol intake). It's a ridiculous argument. There is no logical reason why anyone could not stay away from alcohol for nine months."

Heavy drinking is known to cause birth defects in newborns.

"We really don't know if there is a safe level of alcohol consumption. Fetal alcohol syndrome has been described in mothers who had a single episode of binge drinking," added Dr. Ron Jaekle, a professor of clinical obstetrics and gynecology at University of Cincinnati Health. "I'm not aware that being a non-drinker for nine months out of your life is going to cause a major health problem."

The researchers, from University College London, in London, and publishing online Oct. 6 in the Journal of Epidemiology and Community Health, did point out that the study did not prove any cause-and-effect relationship.

A previous study by the same group of researchers found that a mother's light drinking during pregnancy was not harmful to the child, but this study took it two years further.

This time, the researchers grouped more than 11,500 children born in Britain according to how much their mothers reported drinking during pregnancy.

The groupings were: teetotalers (women who didn't drink during pregnancy but did before and after); light (one to two drinks a week or on occasion); moderate (three to six drinks a week or three to five at one sitting); and binge/heavy drinking (seven or more drinks a week or six on any single occasion).

Six percent of the mothers classified themselves as full-time teetotalers; 60% didn't drink during the pregnancy (but did at other times); about 26% were light drinkers; 5.5% reported being moderate drinkers; while 2.5% claimed to be heavy consumers of alcohol.

Boys whose mothers were light drinkers during pregnancy were 33% less likely and girls 31% less likely to have behavioral, emotional or intellectual problems than nondrinking mothers.

Both boys and girls in this category were also less likely to have hyperactivity: 27% and 29%, respectively, and scored higher on measures of cognitive functioning.

The opposite was true of children born to mothers who were heavy drinkers. These children were more likely to have problems across the board.

The fact that researchers relied on the mothers' own estimates of how much they were drinking may have skewed the results, noted one expert.

"They based much of their conclusions on what the moms told them and I don't think that's a very vigorous or scientific way of looking at the data," said Jaekle, who has observed instances of his own patients grossly underreporting their alcohol consumption.

And the findings may not be applicable to other populations such as the United States.

"Our population is much more heterogeneous and we have certain populations, for example American Indians, who have an enzyme deficiency that causes them to be much more strongly affected by alcohol, so even light drinking may be harmful," he said.

"Recreational drinking could easily be curbed during pregnancy and that would be the safest thing to do," said Katz, who added that he did not know what to make of higher scores in the light-drinking group. "The March of Dimes is not changing its recommendations."