Sexual Intercourse for Induction of Spontaneous Onset of Labor: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

INTRODUCTION: Sexual intercourse during pregnancy is commonly believed to trigger the onset of contractions and, therefore, labor. However, in low-risk pregnancies, there is neither association with preterm birth, premature rupture of membranes, or low birth weight, nor with spontaneous onset of labor at term. AIM: To evaluate the effectiveness of sexual intercourse for spontaneous onset of labor at term in singleton pregnancies. METHODS: The systematic search was conducted using electronic databases from inception of each database to June 2019. Review of articles also included the abstracts of all references retrieved from the search. Inclusion criteria were randomized controlled trials comparing sexual intercourse in singleton low-risk pregnancies at term with controls (either reduced number of coitus or no coitus) for spontaneous onset of labor. Estimates were pooled using random-effects meta-analysis. MAIN OUTCOME MEASURES: The primary outcome was the incidence of spontaneous onset of labor. The summary measures were reported as summary relative risk with 95% CI using the random-effects model of DerSimonian and Laird. RESULTS: Data extracted from 3 trials, including 1,483 women with singleton pregnancy at term and cephalic presentation, were analyzed. Women who were randomized in the sexual intercourse group had similar incidence of spontaneous onset of labor compared with control subjects (0.82% vs 0.80%; relative risk 1.02, 95% CI 0.98-1.07). CLINICAL IMPLICATION: Sexual intercourse should not be restricted in low-risk term pregnancies. Further studies are needed to properly evaluate the impact of orgasm, penetration, condom use, frequency of intercourse and other factors on induction of labor at term. STRENGTH & LIMITATIONS: Our study has several strengths. The three included trials had low risk of allocation bias; intention-to-treat analysis was used; this is the first meta-analysis on this issue so far. Limitations mainly depend on the design of the included studies. Firstly, compliance to the protocol relied on self-reporting by patients; in addition, not all the features of sexual intercourse could be adequately assessed (orgasm, nipple stimulation, sexual positions, etc.). CONCLUSION: In women with singleton, cephalic, low-risk pregnancies, sexual intercourse at term does not significantly increase the incidence of spontaneous onset of labor.