The combination of smoking and drinking 'may synergistically affect the developing immune system. However, our data suggest that maternal alcohol use increases the risk of newborn infections, even if she did not smoke.'

"Excessive alcohol use, especially during the second trimester, increased the risk of newborn infection by more than three times relative to babies whose mothers reported not drinking alcohol in the second trimester," researcher Theresa Gauthier, an assistant professor of pediatrics and attending neonatologist at Emory University, in Atlanta, said in a prepared statement.

The findings appear in the June issue of Alcoholism: Clinical and Experimental Research.

Infection Diagnosed Soon After Delivery

Gauthier's team studied 872 Atlanta-area mothers and their babies. Mothers were asked about their alcohol and tobacco use just prior to conception and during their pregnancy.

Fifty-one of the infants -- just under 6 percent -- had an infection diagnosed soon after delivery.

"Mothers who reported alcohol use, excessive drinking or smoking in pregnancy were more likely to have a newborn diagnosed with an infection than were mothers who reported abstaining from alcohol or cigarettes," Gauthier noted.

Smoking and Drinking

The study also found that smoking by women at any time before and during pregnancy increased the risk of newborn infection, and the Atlanta team found that many of the women who drank alcohol while pregnant also smoked.

Because maternal smoking is known to raise a newborn's infection risk, the combination of smoking and drinking "may synergistically affect the developing immune system," Gauthier speculated. "However, our data suggest that maternal alcohol use increases the risk of newborn infections, even if she did not smoke."

More information: The March of Dimes has more about drinking during pregnancy.