The prevalence and complications of Mycoplasma genitalium and Chlamydia trachomatis infections among women undergoing termination of pregnancy were studied in this nested case-control study at Malmo University Hospital, Sweden, during 2003 to 2007. The study comprised 2079 women presenting for termination of pregnancy. Forty-nine women with M. genitalium infection and 51 women with C. trachomatis infection, together with 168 negative control women, were evaluated. The prevalences of M. genitalium and C. trachomatis were 2.5% and 2.8%, respectively. The M. genitalium was strongly associated with post-termination pelvic inflammatory disease (odds ratio 6.29, 95% CI 1.56-25.2). The increased risk for pelvic inflammatory disease associated with M. genitalium infection after termination of pregnancy suggests a causal relationship.