Some expecting couples are told that having intercourse close to term can induce labor, but a recent review of medical studies suggests that sex may not have this effect.
The analysis, published online in September in the Journal of Sexual Medicine, focused on women with singleton (one baby), cephalic (head-first orientation), low-risk pregnancies.
Scientists have proposed several explanations on why intercourse could prompt labor. For example, semen contains compounds called prostaglandins, which are associated with labor. And uterine contractions are possible during female orgasm. However, studies on the subject have had contrasting results.
The current study was a systematic review and meta-analysis of three randomized controlled trials involving 1,483 women with low-risk singleton pregnancies at term. Two trials took place in Malaysia; the third was conducted in Portugal.
Some women were instructed to have sex toward the end of their pregnancy. One study asked the control group to avoid sex altogether. Control groups in the two other studies were “neither encouraged nor discouraged” to have intercourse.
Labor was defined as a cervical dilation of at least three centimeters.
The researchers found that sex didn’t appear to hasten labor onset, writing, “We did not find significant differences in the spontaneous onset of labor for women advised to have coitus compared to control subjects.”
But they did note some limitations in the research. For instance, it was unknown whether regular sexual activity throughout the pregnancy was more effective for inducing labor than “brief stimulation close to term.” Also, most information on sexual activity came from the women’s self-report.
The authors concluded that sexual intercourse need not be restricted in women with low-risk pregnancies, but might be inadvisable for women with high-risk pregnancies. Additional research was needed to confirm the findings, they said.
They suggested further research concerning labor onset and other factors, such as sexual frequency, sexual positions, condom use, and ejaculate volume. However they admitted that such studies could be difficult to plan. They also questioned to what degree masturbation might affect onset of labor.
The Journal of Sexual Medicine
Carbone, Luigi, MD, et al.
“Sexual Intercourse for Induction of Spontaneous Onset of Labor: A Systematic Review and Meta-Analysis of Randomized Controlled Trials”
(Full-text. Published online: September 11, 2019)