Middle class women are more likely than women from other classes to drink more than the recommended limits during pregnancy, researchers said.
They called for health officials to revise their guidance on drinking in pregnancy after their study showed that even those adhering to the suggested limits are more likely to have problems with their babies than those who do not drink at all.
More than half of women drink more than the recommended limits during the first three months of pregnancy, a study has suggested.
Some 53% of women drank more than the upper limit of two units a week during the first trimester, with middle class women are more likely than women from other classes to drink more than the recommended limits during pregnancy, figures show.
The study, published in the Journal of Epidemiology and Community Health, examined 1,200 women in Leeds who filled out food frequency questionnaires, including information on alcohol consumption during the month before conception and the three trimesters of pregnancy.
If a woman drank more than two units a week during the first three months of pregnancy they are twice as likely to have a baby who was born "small for gestational age" when compared to non-drinkers, the researchers found.