Moderate consumption of alcohol by pregnant women appeared not to harm their children's brain development in a new large-scale study of families in southwestern England.

Although most of the mothers had not drank heavily while pregnant, typical drinking patterns — as opposed to binging or abstaining — were associated instead with slightly better neurodevelopmental outcomes, as measured by observational study of balance.

However, the association between drinking in pregnant women and improved outcomes in their children were most likely confounded by other factors, including the higher social position of women who drink moderately.

"We found no strong evidence for adverse effects of typical general population levels of maternal alcohol use during pregnancy on balance outcomes in school-age offspring," the study authors reported Monday in BMJ Open. "Paradoxical 'beneficial' effects found in some analyses were most likely a reflection of residual confounding by factors related to social position."

The researchers, from the University of Bristol, also said the ostensible benefits to maternal drinking during pregnancy, as seen in animal and human studies, were mostly likely noncausal. In this longitudinal look at nearly 7,000 children and their parents, most of the mothers — 95.5 percent — had consumed either no alcohol or only a moderate amount. At 18 weeks pregnant, slightly more than 70 percent reported no alcohol consumption, while 14 percent said they drank no more than a couple per week, with 10.7 percent reporting three to seven alcoholic drinks.

Of all of the pregnant women, 4.5 percent engaged in binge drinking while another 4.5 percent completely abstained from alcohol during pregnancy. While heavy drinkers were more likely to be of lower socioeconomic status, moderate drinkers enjoyed a higher social position than either binge drinkers or teetotalers.

Among the 10-year-old children in the study, researchers found no evidence of adverse effects from maternal drinking when measuring balance, but noted that previous research had connected fetal alcohol exposure to neurodevelopmental problems when using other measurements. The children were tested on two measures, including a timed crossing of a 2-meter balance beam while walking heel-to-heel with either eyes open or closed, and standing on one leg, with eyes open or closed, for 20 seconds.

"A recent systematic review found no strong evidence of effects of prenatal maternal alcohol exposure at levels typically seen in the general population on offspring balance, but noted important limitations in the current evidence base including an absence of large general population-based prospective studies with adequate measures of both alcohol exposure and balance outcomes," the researchers wrote.

Similarly, the study did not find a link between adverse outcomes with regard to balance — a central neurodevelopmental ability underpinning many motor skills — and paternal drinking, which had been suggested by previous study in animals.

In reviewing other studies on the subject, researchers said a previous longitudinal study — finding a lesser balance ability among four-year-olds whose mothers had drank during pregnancy — may have oversampled heavy drinkers.

Source: Humphriss, Rachel, Hall, Amanda, May, Margaret, Zuccolo, Luisa, Macleod, John. Prenatal Alcohol Exposure And Childhood Balance Ability: Fndings From A UK Birth Cohort Study. BMJ Open. 2013.