Objective: Our aim was to investigate the influence of vaginal colonization with specific microorganisms on the relationship between sexual intercourse during pregnancy and preterm delivery.
Study design: As part of a multicenter, prospective study interviews and physical examinations were conducted with and genital cultures were obtained from women seeking prenatal care from 23 to 26 weeks' gestation. At 31 to 36 weeks interviews were conducted with a randomly selected sample of these patients.
Results: Frequent intercourse (defined a priori as once per week or more) at 23 to 26 weeks was associated with a significantly reduced risk of subsequent preterm delivery in women without Trichomonas vaginalis, Mycoplasma hominis, or bacterial vaginosis, possibly because of the relative health and lack of complications in the pregnancies of those women engaging in sexual intercourse. Frequent intercourse was not significantly associated with preterm delivery in women with T. vaginalis, M. hominis, or bacterial vaginosis. Neither T. vaginalis, M. hominis, nor bacterial vaginosis was associated with preterm delivery among women with infrequent intercourse at 23 to 26 weeks. However, T. vaginalis and M. hominis were risk factors for preterm delivery among those with frequent intercourse.
Conclusions: Frequent sexual intercourse by itself is not associated with an increased risk of preterm birth. However, women who are colonized with specific microorganisms and who engage in frequent intercourse are at increased risk of preterm delivery.