Research: Sex during pregnancy does not lead to preterm delivery

Chapel Hill -- Contrary to longstanding belief among some doctors and the public, sexual activity during pregnancy does not lead to premature delivery, a new University of North Carolina at Chapel Hill study indicates. Except for problem pregnancies, during which couples should follow medical advice carefully, sex that is not uncomfortable appears to be as safe as any other reasonable physical activity.

The research, conducted at the UNC-CH School of Public Health, involved analyzing self-reported sexual intercourse and orgasm among 187 N.C. women who delivered prematurely between 29 and 36 weeks gestation and 409 other pregnant women who served as control subjects. None of the latter group had delivered prematurely at the time of the confidential interviews.

"We cannot exclude the possibility that sexual activity might be a risk for a small subgroup of susceptible women," said Dr. Amy Sayle and colleagues. "As a whole, however, continued sexual activity during late pregnancy was a strong predictor that a pregnancy will go full term." A report on the findings appears in the February issue of Obstetrics & Gynecology.

Besides Sayle, who used the study to earn her doctorate in epidemiology in 1998, authors are Drs. David A. Savitz, professor and chair of epidemiology; John M. Thorp, associate professor of obstetrics and gynecology; and Irva Hertz-Picciotto, professor of epidemiology, all at UNC-CH. Dr. Allen J. Wilcox, chief of the epidemiology branch at the National Institute of Environmental Health Sciences and an adjunct UNC-CH faculty member, also participated. Sayle is now a part-time instructor at Duke University and a Chapel Hill-based research and teaching consultant.

In the study, Sayle analyzed interviews conducted with the Piedmont N.C. residents after delivery for those who gave birth prematurely and before delivery for the control women who were still pregnant. Typically, human pregnancies last about 40 weeks.

She found a reduced risk of preterm delivery within two weeks of both sexual intercourse and orgasm among the women.

"Adjusting for race, age, education and living with a partner had little effect on results," Sayle said. "The women who delivered prematurely were more likely than controls to report poorer health, medically related reasons for reducing sexual activity, less interest in sex and receipt of advice to restrict sexual activity during pregnancy."

While it is possible that sex reduces the risk of preterm delivery and has some protective effect, it appears more likely that women with problem pregnancies are more likely to abstain from sexual activity, she said.

"It's just very difficult to separate out the effects of being sexually active in late pregnancy from the reasons for being sexually active," the scientist said.

She conducted the study because preterm delivery is an important cause of infant death before and after birth and of illness following delivery. Previous studies of the kind she and her colleagues did have yielded conflicting results, and some contained design flaws she tried to avoid. The new work, which adds to the growing body of knowledge suggesting that sex is generally not harmful during pregnancy, is part of a larger investigation titled "Pregnancy, Infection and Nutrition," which Savitz leads.

"We hope our work will help women avoid some needless worrying during pregnancy," Sayle said. "More than half the women in our study reported that their doctors had not said anything to them about sex."

Note: Sayle can be reached via e-mail at [email protected]

School of Public Health contact: Lisa Katz, 966-7467