A prospective preconception cohort study of the association between Mycoplasma genitalium and fecundability in Kenyan women trying to conceive

STUDY QUESTION: Is Mycoplasma genitalium-infection associated with reduced fecundability? SUMMARY ANSWER: Preconception M. genitalium-infection was associated with 27% lower fecundability though confidence intervals were wide, and the association between M. genitalium and fecundability may be dependent on concurrent bacterial vaginosis (BV). WHAT IS KNOWN ALREADY: M. genitalium has been associated with cervicitis, pelvic inflammatory disease, infertility, and preterm birth, but the extent to which M. genitalium is causally related to adverse reproductive sequelae in women is debated. STUDY DESIGN, SIZE, DURATION: Kenyan women enrolled in a prospective preconception cohort provided vaginal fluid specimens and underwent monthly pregnancy testing. Stored samples from 407 women who had been trying to conceive for <= 6 months were tested for M. genitalium using a nucleic acid amplification test. PARTICIPANTS/MATERIALS, SETTING, METHODS: Data on first day of last menstrual period, sexual behavior, pregnancy status, and vaginal specimens were collected at monthly preconception visits. The association between M. genitalium detected at the visit prior to each pregnancy test and fecundability was estimated using discrete time proportional probabilities models. Secondary analyses explored the influence of concurrent BV on the association between M. genitalium and fecundability. MAIN RESULTS AND THE ROLE OF CHANCE: The 407 participants experienced 1220 menstrual cycles and 213 pregnancies. The prevalence of M. genitalium at enrollment was 7.7%. After adjustment for age, frequency of condomless sex in the last 4 weeks, and study site, M. genitalium was associated with a 27% lower fecundability, but confidence intervals were wide (adjusted fecundability ratio (aFR) 0.73, 95% CI 0.44, 1.23). In secondary analyses, when compared to cycles without M. genitalium or BV at the visit prior, women with both M. genitalium and BV at the visit prior had a 51% lower fecundability (aFR = 0.49, 95% CI 0.22, 1.09) whereas there was no association of M. genitalium alone (aFR = 0.98 (95% CI 0.54, 1.76)), and a smaller reduction in fecundability for women with BV only (aFR = 0.80 (95% CI 0.60, 1.07)). LIMITATIONS, REASONS FOR CAUTION: Results should be interpreted cautiously given the relatively low prevalence of M. genitalium and wide confidence intervals. WIDER IMPLICATIONS OF THE FINDINGS: In this cohort of Kenyan women trying to conceive, the association between M. genitalium and fecundability was influenced by concurrent BV status, suggesting there may be a synergistic effect of M. genitalium and BV on fecundability.