Ten percent of pregnant women in the U.S. report drinking alcohol during their pregnancy, a report from the Centers for Disease Control and Prevention reveals.

For pregnant women age 35 or older, that figure rises to 35 percent, the CDC says.

Of greater concern is that of the women who admit to drinking, around a third say they've engaged in binge drinking, defined as consuming at least four alcoholic drinks on a single occasion, the report authors say.

The frequency of binge drinking among pregnant women was significantly higher at 4.6 incidents than it was among non-pregnant women, at 3.1 incidents, the researchers found.

"One possible explanation for this might be that women who binge drink during pregnancy are more likely to be alcohol-dependent than the average female binge drinker, and therefore binge drink more frequently," says epidemiologist Cheryl Tan, one of the authors of the report issued as part of the CDC's Morbidity and Mortality Weekly Report.

Researchers at the CDC's National Center on Birth Defects and Developmental Disabilities and its National Center for Chronic Disease Prevention and Health Promotion participated in preparing the report.

The report was based on data collected as part of the Behavioral Risk Factor Surveillance System between 2011 and 2013, when more than 200,000 women between 18 and 44 — childbearing age — were called in a random telephone sample of households in the 50 states and the District of Columbia.

The report highlights the need for greater efforts to educate women about the dangers of alcohol consumption during pregnancy, the researchers wrote.

"There is a need for a comprehensive approach to reduce alcohol use and binge drinking among pregnant women," they said.

The study findings highlight the need for stronger screening, education and, if necessary, intervention in alcohol use, they add.

"Women who are pregnant or might be pregnant should be aware that there is no known safe level of alcohol that can be consumed at any time during pregnancy," says Tan. "All types of alcohol should be avoided, including red or white wine, beer and liquor."

That warning agrees with guidelines from the American College of Obstetricians and Gynecologists, which cautions "no amount of alcohol consumption can be considered safe during pregnancy."

Drinking during pregnancy increases the risk of fetal alcohol syndrome, the group says, leading to severe physical and mental defects in newborns, and also puts pregnant women at risk of miscarriage or stillbirth.