Pregnant women who enjoy a glass of wine each week will not harm their baby's development.
British researchers claim the latest findings should make mothers feel more relaxed about the occasional tipple.
The study of 11,000 mothers found light drinking during pregnancy did not harm babies.
Women can safely drink a 175ml glass of wine, a 50ml glass of spirits or just under a pint of beer each week without damaging their child's intellectual or behavioural development, the study found.
A team at University College London questioned mothers when their babies were nine months old about their drinking during pregnancy and other aspects of their health and wellbeing.
Visits were also made to the families when the children were seven, says a report in BJOG: An International Journal of Obstetrics and Gynaecology.
Tests were carried out to assess their development in maths, reading and spatial skills, and questions were asked about their social and emotional behaviour.
The results showed boys and girls born to mothers who had one or two units of alcohol per week scored slightly higher on some tests than those born to non-drinkers.
They were also likely to have lower scores for behavioural problems than children of mothers who abstained, although adjustment for other factors diminished the differences. Professor
Yvonne Kelly, who led the research team, said: "There appears to be no increased risk of negative impacts of light drinking in pregnancy on behavioural or cognitive development in seven-year-old children.
"While we have followed these children for the first seven years of their lives, further research is needed to detect whether any adverse effects of low levels of alcohol consumption in pregnancy emerge later in childhood."
Heavy drinking in pregnancy is linked to foetal alcohol spectrum disorder in children, which can cause a range of physical, mental and behavioural problems.
The issue of how much is safe to drink during pregnancy has caused controversy in recent years.
John Thorp, BJOG's deputy editor-in-chief, said: "It remains unclear as to what level of alcohol consumption may have adverse outcomes, so this should not alter current advice. "If women are worried about consumption levels, the safest option would be to abstain from drinking during pregnancy."