(RxWiki News) It's clear that heavy drinking while pregnant can harm a baby. But research has been less clear about whether only a few drinks makes a difference. Until now.
A recent study has found that even small amounts of alcohol during pregnancy might impact a child's IQ.
These researchers think it's possible that women who drink even small amounts during pregnancy and have the genetic variants which metabolize alcohol more slowly might be exposing their baby to more alcohol for a longer period of time.
"Don't drink alcohol while pregnant."
The study, led by Sarah J. Lewis, of the School of Social and Community Medicine at the University of Bristol in the United Kingdom, took a different approach than past studies on the effects of small amounts of alcohol during pregnancy.
This study looked at genetic variations related to how the body metabolizes alcohol in 4,167 children and their mothers.
Some variations lead people to metabolize alcohol quickly while others cause the body to metabolize it more slowly, which means the alcohol is in the person's body for longer and at higher levels.
Past studies have only been able to observe correlations between how much a mother drank while pregnant and how her children performed on assessments later.
But when the amount of alcohol being consumed was not small – such as one to six units a week – it was hard to distinguish between what might be attributed to prenatal exposure to alcohol and what might result from lifestyle factors.
Smoking, diet, socioeconomic status, a mother's age and her level of education might play a part in a child's cognitive skills as well as the alcohol.
In this study, the mothers filled out questionnaires when they were 18 weeks pregnant and 32 weeks pregnant describing how often they drank alcohol and how much they drank.
Even having less than one unit (10ml of ethanol) of alcohol a week was classified as drinking during pregnancy for this study. A unit is roughly equivalent to a small glass of wine, a glass of spirits or half a pint of beer.
Then the children's IQ was tested when they were 8 years old. The researchers found that the IQ of children whose mothers drank moderately during pregnancy dropped an average of almost two points for each change found in the four genetic variations the researchers looked at.
But the children of women who did not drink at all during pregnancy did not show any reductions in IQ even if they had the same genetic variations.
Even though past studies have shown higher IQ among children of women who had only a few drinks a week while pregnant, these women often came from healthier and higher socioeconomic or educational backgrounds, which is already linked to a higher IQ in children.
"This is a complex study but the message is simple: even moderate amounts of alcohol during pregnancy can have an effect on future child intelligence," said senior author Ron Gray in a release about the study. "So women have good reason to choose to avoid alcohol when pregnant."
The study was published November 14 in the journal PLOS ONE. The research was funded by the UK Medical Research Council, the Wellcome Trust and the University of Bristol. The authors declared no conflicts of interest.
