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Feb. 8, 2001 -- The idea that continuing to engage in sexual activity in the last trimester of your pregnancy increases your risk of premature delivery appears to be unfounded for most healthy women.
While it's true that a small amount of substances known to trigger labor are found in the man's semen and are released when the woman's nipples are stimulated and during the female orgasm, doctors say the risk of labor isn't high enough to warn most women and their partners against making love in the weeks prior to their term (37 weeks).
"We found no evidence that sexual activity in late pregnancy increased a woman's risk of preterm delivery between 29 and 36 weeks' gestation," reports Amy E. Sayle, PhD, lead author of a study published in the February issue of the journal Obstetrics & Gynecology.
Through interviews in which women were asked explicit questions about their sexual activity before and during pregnancy, the researchers found that women had less interest in sex between 29 and 36 weeks. But those who had sex between 27 and 36 weeks of pregnancy had an even lower risk of preterm delivery than women who abstained from sex during that period.
According to Sayle and colleagues, one explanation for the finding may be that some women find sex to be comforting and supportive, which may be important for the pregnancy to run its natural course. Another explanation could be that women who maintain an interest in sex throughout their pregnancy may be healthier and at lower risk for problems, whereas women who don't feel well and are having problem pregnancies are more likely to intentionally avoid sex.
The finding that sex is unlikely to lead to early delivery may be disappointing news to some women who intentionally engage in sex close to their due date in hopes of triggering labor sooner.
"Stimulating the nipple works in some cases," Mary Wilson, MD, tells WebMD. The stimulation is another way to release the substance known to trigger labor and cause the uterus to contract. "Sometimes it works, sometimes it doesn't ... there is no real research [to show that it works]," says Wilson, a practicing obstetrician in New York who says she doesn't recommend that women try to trigger labor on their own.
Sayle says her study does suggest that a small percentage of women who have risk factors for preterm delivery could further increase their risk by engaging in sex. Risk factors for preterm delivery include having had a previous preterm delivery or other pregnancy-related problem, contracting certain vaginal infections, having uterine bleeding during your pregnancy, and smoking, drinking alcohol, or using drugs.
Wilson says she sometimes tells women who have any of these risk factors to use condoms and to avoid orgasm late in pregnancy. Taking both those precautions may reduce the slight risk that the substances released through orgasm and semen will trigger early labor.
Other obstetricians and high-risk pregnancy experts do advise women at risk of preterm delivery to avoid intercourse. Ask your doctor about your risk factors and whether or not you should engage in sexual activity.