The "drinking for two" phenomenon may be more prevalent than previously thought. One in 13 pregnant women drink booze, with one out of five of these women admitting to binge drinking, according to a study released yesterday by the Centers for Disease Control and Prevention. Researchers examined data from 345,076 women aged 18-44 from a behavioral survey conducted between 2006 and 2010. Of the women studied, 4% were pregnant, and 7% of these women drank alcohol. A prior study from Sweden revealed a slightly higher percentage of women who drink while pregnant, at 12%, but in more moderate amounts—mind you, that study concerned women in Europe, the world's booziest continent. This study suggests one in five pregnant drinkers in the US consumes up to six drinks per session. "These results indicate that binge drinking during pregnancy continues to be a concern," write the researchers, led by the CDC's Claire M. Marchetta. The women who admitted to binge drinking while pregnant were mostly aged 18-24, and mostly did so three times per month or more. Unmarried women were also more likely to drink excessively. Back in June, five different Danish studies reported that drinking moderate amounts of alcohol while pregnant may be safe. However, the CDC contends that drinking any amount of alcohol while pregnant is dangerous, and can lead to conditions including fetal alcohol syndrome and birth defects.