The latest Centers for Disease Control and Prevention update recommending that women who are pregnant or could become pregnant abstain from alcohol use prompted a Vanderbilt professor of Obstetrics and Gynecology and her team to explore the patterns of alcohol use in early pregnancy.

Expecting all women who might be or could become pregnant to refrain from alcohol use is not a realistic public health policy, said Katherine Hartmann, MD, PhD, deputy director of the Institute for Medicine and Public Health at Vanderbilt and the senior author of a study recently published in the journal Obstetrics & Gynecology.

The study, “Pregnancy Intention and Maternal Alcohol Consumption,” found that the vast majority of women with intended as well as unplanned pregnancies either stopped or decreased drinking after having a positive pregnancy test.

“Our study was not focused on whether or not alcohol is safe in the early conception window,” Hartmann said. “We wanted to see what actual women were currently doing. And we were pleasantly surprised about how promptly people changed their alcohol use — most quitting completely and about 6 percent of women continuing to consume some alcohol, almost all of them at very low levels.

“Women were already self–regulating their alcohol use. Our findings suggested that promoting early pregnancy awareness could prove to be more effective than promoting abstinence from alcohol among all who could conceive.”

Hartmann said data from the Guttmacher Institute reports that there are 61 million reproductive–age women in the United States, with 43 million deemed potentially at risk of becoming pregnant. She said it was highly unlikely to expect women to completely forgo alcohol use because they are at risk of becoming pregnant.

Hartmann and colleagues reviewed the data reported by participants enrolled in Right from the Start, a study of early pregnancy health conducted in eight metropolitan areas around the U.S. by investigators at Vanderbilt and the University of North Carolina–Chapel Hill. The study, funded by the National Institute of Child Health and Human Development, includes more than 5,000 women.

Their findings suggest an alternative public health strategy — providing easy access to low–cost pregnancy tests to assure early pregnancy testing. Although they did not study contraceptive use, the authors also note that access to reliable contraception for those who don’t intend to conceive is the optimal means of preventing alcohol exposure in unintended pregnancies.

“Although our study does not test these approaches, our findings imply that pregnancy prevention and access to inexpensive pregnancy tests with encouragement to test early around the time of a missed period would be a stronger strategy to prevent alcohol exposure in pregnancy,” she said.

“At the time of a missed menstrual period, we say that someone is four weeks pregnant, but actually, the embryo is only two weeks old with only a limited time in the uterus with exposure to maternal tissue.”

Before that, says Hartmann, the embryo is moving through the fallopian tube into the uterus.

“Around the time of a positive pregnancy test is about the time that a developing embryo could be exposed, theoretically, to maternal alcohol byproducts. And in that early window, exposure should be very low because there is not yet a full maternal fetal circulation.”

Hartman said it was reassuring that women are recognizing the hazards of alcohol use during pregnancy and modifying habits, but it is most useful the earlier they are aware of a pregnancy.