ATLANTA (AP) _ Pregnant women are drinking harder than they did four years earlier, raising the risk their babies will suffer mental retardation, learning disorders and other problems, the government reported Thursday.

A telephone survey by the Centers for Disease Control and Prevention found that 3.5 percent of 1,313 moms-to-be in 1995 admitted they had seven or more drinks per week or binged on five or more drinks at once within the previous month. That's up from 0.8 percent of 1,053 pregnant women in 1991.

``Even though those numbers seem small, that's a pretty significant increase,'' CDC statistician Beth Luman said.

The sample suggests that 140,000 pregnant women nationwide were frequent drinkers in 1995, compared with 32,000 women in 1991, she said.

The CDC also said 16.3 percent of the pregnant women in 1995 had at least one drink in the preceding month, compared with 12.4 percent in 1991.

Louise Floyd, chief of the CDC's fetal alcohol syndrome prevention section, said the reason for the increase is unclear. CDC researchers are going back through the survey to find out.

Drinking while pregnant can cause fetal alcohol syndrome, a lifelong condition that can include retardation, facial abnormalities, stunted growth and learning disorders.

Ms. Floyd said researchers are finding some harmful effects from three or four drinks a week. ``No drinking is safe while you're pregnant,'' she said.

The 1995 survey questioned 33,585 randomly selected women _ pregnant or not _ ages 18 to 44. Of the total, more than half said they drank at least once within the past month and 12.6 percent were frequent drinkers, or those who have at least seven drinks a week or five or more at once. The percentages were similar to the 1991 figures, the CDC said.

The drinking rates among women in 1995 were highest in Wisconsin, Iowa and Pennsylvania.

In 1981, the U.S. surgeon general first urged women _ pregnant or planning to be _ not to drink. Those warnings were repeated by the secretary of health and human services in 1990 and 1995.

Claire Coles, an expert on fetal alcohol syndrome, speculated that people may simply be more honest about owning up to their drinking. But she said that in any case, obstetricians and gynecologists need to talk to their patients about alcohol.

``Anyone who is working with pregnant women should look at a 3.5 percentage and realize they should be asking women more questions,'' said Ms. Coles, a professor of psychiatry at Emory University in Atlanta. ``We keep talking about this, yet I'm not sure everyone is convinced drinking while pregnant is dangerous.''