Late-Pregnancy Sex Doesn't Speed Labor
New Study Rejects 'Old Wives' Tale', Shows Late Pregnancy Sex Generally Safe
WebMD News Archive
June 2, 2006 - The notion that having sex late in pregnancy will hasten labor and
delivery is among the oldest of old wives' tales. But it looks like
the old wives were wrong.
Women with a low risk of complications who had sex in the final weeks of
pregnancy actually carried their babies slightly longer than those who
abstained from sex during that time, according to a new study reported in the
June issue of Obstetrics and Gynecology.
And the full-term babies born to women who had late-pregnancy sex were just
as healthy as those born to women who did not.
"This study should reassure low-risk women that there is probably no
harm in engaging in intercourse late in pregnancy," says obstetrician
Jonathan Schaffir, MD, of the Ohio State University Medical Center. "But it
showed no particular benefit, either, in terms of inducing labor."
Sex Wasn't a Factor
There is actually sound medical reasoning for the idea that sex might bring
on labor. Male semen contains hormone-like chemicals known as prostaglandins.
Prostaglandins can be used for cervical ripening, in which the cervix
physically changes in preparation for labor. Also, female orgasm can bring on
But there is little clinical evidence that intercourse influences the
outcome of normal pregnancies. The study cites one analysis of 59 studies that
found no association between sex and preterm birth, premature amniotic sac
rupture, or low birth weight in low-risk pregnancies.
Schaffir's study included 93 low-risk pregnant women past the 37th week of
their pregnancy. (At 37 weeks a pregnancy is considered full term.) The women
were asked during weekly doctor's office visits about their sexual
Half the women reported having sex involving penetration after that
Cervical examinations were performed at each weekly visit to determine if
sexual activity affected cervical ripening. No correlation was seen between the
frequency of sexual intercourse and cervical change.
And the sexually active women in the study actually carried their babies an
average of four days longer than women who abstained from sex -- 39.9 weeks
compared with 39.3 weeks. Schaffir says this small difference could be because
women closer to labor simply felt less comfortable and were, therefore, less
likely to engage in sex.
The lack of a difference in cervical changes, combined with the absence of a
meaningful difference in delivery dates among women who had sex, suggests
sexual intercourse had no effect on inducing labor, the researchers