Sex close to due date may cause spontaneous labor

Women who have sexual intercourse during late pregnancy are more likely than abstinent women to have a spontaneous delivery at 38 to 40 weeks' and less likely to require labor induction, according to results of a study conducted in Malaysia.

It is commonly believed that coitus hastens labor, but very little research has been published to confirm this theory, Dr. Peng Chiong Tan and associates point out in the medical journal Obstetrics and Gynecology.

Tan, from the University of Malaya in Kuala Lumpur, and colleagues designed a study in which 200 healthy, married women with uncomplicated pregnancies completed diaries regarding sexual activity beginning at week 36 of pregnancy. Labor induction was carried out among women who had not delivered after about 41 weeks of pregnancy.

The women's diaries showed that 116 (58 percent) of women had intercourse in late pregnancy an average of four times. Twenty-five women required labor induction because of prolonged pregnancy.

The results showed that 6.9 percent of sexually active women had not delivered by 41 weeks, compared with 29.8 percent of abstinent women.

After factors such as ethnicity, education, occupation, perception of coital safety and husbands' age were taken into account, women who had sexual intercourse were 90 percent more likely to have delivered by 41 weeks and almost 100% had a less likely to require labor induction compared with women not engaging in sexual intercourse.

Tan's team also found that having intercourse more than once per week was inversely associated with prolonged pregnancy and the need for labor induction.

Although the researchers recommend sexual intercourse as a means of avoiding labor induction, they add that "in potentially compromised pregnancies caution has to be applied because the effect of intercourse and orgasm has been described as being similar to an oxytocin contraction stress test."

SOURCE: Obstetrics and Gynecology, June 30, 2006.