Light drinking in pregnancy has no effect on premature birth, small babies or low birthweight, research suggests.
Experts reviewing 36 studies on the issue found no link between low to moderate amounts of alcohol and three major risks to a baby.
However, the research did confirm previous studies which have shown heavy drinking in pregnancy increases the chance of a baby being born premature, small for their gestational age or too light.
Government advice says pregnant women and those trying to conceive should avoid drinking alcohol.
If women do choose to drink, they should drink no more than one or two units of alcohol once or twice a week and should avoid getting drunk.
Previous studies on the risks of light to moderate drinking in pregnancy have shown mixed results.
The study found a “cut off” of 10g to 18g alcohol a day above which there were risks to the growing foetus.
The more women had to drink above this level, the higher the risks, but there were no apparent problems below 10g a day.
Heavy drinkers – those consuming 36g a day – were 23 per cent more likely to have a premature birth than those who did not drink and were more likely to have a small baby.
In the UK, one unit is 8g of alcohol, equivalent to a pub measure of spirits, half a standard glass (175ml) of wine and half a pint of 3.5 per cent beer, cider or lager.
Writing in BJOG, an International Journal of Obstetrics and Gynaecology, the researchers concluded: “Dose-response relationship indicates that heavy alcohol consumption during pregnancy increases the risks of all three outcomes whereas light to moderate alcohol consumption shows no effect.” They added: “This analysis adds weight to previous findings that light to moderate alcohol consumption during pregnancy does not increase the risks of low birthweight, pre-term birth and small for gestational age.”
Philip Steer, professor and editor-in-chief of the journal, said: “This new study builds on previous studies that have linked heavy drinking to adverse effects on the baby and should act as a deterrent to heavy or binge drinking during pregnancy.
“Further research should look at any links between low to moderate drinking and other adverse outcomes.”
Previous studies have shown heavy drinking in pregnancy can cause miscarriage or stillbirth and increase the risk of foetal alcohol syndrome, which can cause developmental problems.
Patrick O’Brien, from the Royal College of Obstetricians and Gynaecologists said: “Women should be careful about the amount of alcohol they consume when pregnant, especially in the first trimester.
“The RCOG advises that if a woman falls pregnant, she should abstain from alcohol.
“However, if she would like to have a drink, the current evidence shows that one or two units, once or twice a week, is acceptable after 12 weeks of pregnancy.
“The findings from this study show that low-level drinking during pregnancy does not result in pre-term birth and smaller babies.
“This does not mean that women can use this as an excuse to indulge in more than the recommended amount in the UK.”
Gail Johnson, education and professional development adviser at the Royal College of Midwives, said: “The RCM urges caution in interpreting the research and that its findings do not send out the wrong messages about pregnancy and alcohol consumption to pregnant women.
“There is still no evidence to suggest what a ‘safe’ consumption limit of alcohol in pregnancy is and there is the potential for further confusion when the amount of alcohol a pregnant woman consumes depends on the size of the glass and the strength of the alcohol she drinks.
“Other critical variables are her BMI and how often she consumes alcohol. We know that a build-up of alcohol consumption can damage the unborn child.”