Few things attract such disparaging glares as a pregnant woman sidling up to the bar and ordering a martini. While studies may come to different conclusions on the topic, boozing and pregnancy are generally frowned upon in our society.

But new research from the University of Leeds has found that for a certain demographic, the rules of drinking while expecting a baby are being ignored, and that those babies are more at risk of being born small and premature.

Who were the defiant moms? Older, affluent white women with college degrees.

The researchers came to their conclusion by assessing responses to food frequency questionnaires completed by 1,264 British women at low risk of birth complications.

The U.K. Department of Health recommends that pregnant women – and those trying to conceive – should abstain from alcohol, or at the most, consume no more than one to two units a week. A unit is defined as 10 ml of pure alcohol, one to two units is equivalent to a glass of wine.

What the researchers found was that more than 50 percent of women in the white-affluent-educated socioeconomic class drank, on average, four units a week in their first trimester and only went down to two units or less in the second. Those who consumed more than the recommended two units a week were twice as likely to give birth to unexpectedly small or premature babies as women who abstained completely.

"Our results highlight the need for endorsing the abstinence-only message, and further illuminate how timing of exposure is important in the association of alcohol with birth outcomes, with the first trimester being the most vulnerable period," the study notes. “Our findings suggest that women should be advised to abstain from alcohol when planning to conceive and throughout pregnancy.”

Drinking during the time before conception was also associated with smaller babies, indicating that this may also be a crucial period, suggest the authors.

“It is interesting that alcohol consumption was greatest in women from a strong economic and social background who should otherwise have the lowest risk of preterm birth and low birth weight,” said Andrew Whitelaw, professor of Neonatal Medicine at Leeds University.

“This is further evidence that even moderate amounts of alcohol are toxic to the growing fetus and direct toxicity is further worsened by the increased complications of premature birth,” he added.

The research was published online in the Journal of Epidemiology and Community Health.

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