Treatment Effects of Genital Mycoplasma Species in High-Risk Pregnant Individuals: A Retrospective Cohort Study

Objective We aimed to estimate the causal effect of treatment for genital <i>Mycoplasma</i> species on preterm birth (PTB) and spontaneous abortion (SA). We also evaluated treatment effects separately for cases with co-infection of <i>Ureaplasma</i> and <i>Mycoplasma </i>species. Methods This was a retrospective observational cohort study at a single center. Singleton mothers with one or more risk factors for PTBs were screened and treated for genital <i>Mycoplasma</i> species. The treatment was repeated based on polymerase chain reaction (PCR) results after each course. We applied inverse probability treatment weighting, and risk differences (RDs) of the treatment effect on pregnancy outcomes were estimated with the generalized estimating equations. A combination of PTB and SA was used as the primary outcome. Secondary analysis was conducted, focusing on treatment for co-infection of both <i>Mycoplasma</i> and <i>Ureaplasma</i> species. Results From January 2014 to December 2020, 696 individuals tested positive for genital <i>Mycoplasma </i>species. Of the individuals, 566 were treated with azithromycin, whereas 62 were not. Among them, 269 received a second treatment, whereas 40 did not. The first treatment effect on PTB and SA was RD (95% CI) of 0.037 (-0.104, 0.178), and the second treatment effect was RD (95% CI) of -0.049 (-0.220, 0.123). When focusing on co-infection of <i>Ureaplasma</i> and <i>Mycoplasma</i>, the first effect was RD (95% CI) of -0.005 (-0.274, 0.264), and the second treatment effect was RD (95% CI) of -0.545 (-0.739, -0.350). Conclusions Routine treatment for genital <i>Mycoplasma</i> species<i> </i>is not recommended. However, the results suggest potential benefits in treating co-infections.