Sexual activity during late pregnancy and risk of preterm delivery

OBJECTIVE: To examine the association between sexual activity during late pregnancy and preterm delivery. METHODS: Women at least 16 years old and carrying singleton fetuses were recruited between 24 and 29 weeks' gestation from prenatal clinics in central North Carolina. They were interviewed by telephone about sexual activity before and during pregnancy. One hundred eighty-seven women delivered between 29 and 36 weeks and had a follow-up interview after delivery. Four hundred nine women who were selected randomly from the cohort served as controls and had a follow-up interview between 29 and 36 weeks (mean gestational age 39.2 weeks). RESULTS: Intercourse during late pregnancy was associated with a reduced risk of preterm delivery. The conditional odds ratio (OR) was 0.34 and 95% confidence interval (CI) 0.23, 0.51 for preterm delivery within 2 weeks after intercourse. Similar decreased risk for preterm delivery was found with recent female orgasm. Adjusting for race, age, education, and living with a partner had little effect on results. Cases were more likely than controls to report poorer health, medical reasons for reducing sexual activity, less interest in sex, and receipt of advice to restrict sexual activity during pregnancy. Results did not differ substantially according to presence or absence of bacterial vaginosis at 28 weeks. CONCLUSION: These data provide evidence against the hypothesis that sexual activity generally increases risk of preterm delivery between 29 and 36 weeks. However, we cannot exclude the possibility that a small subgroup of susceptible women might have adverse consequences of sexual activity.