A new study published in the American Journal of Obstetrics and Gynecology investigated Ureaplasma parvum serovar specific pathogenicity in a large clinical cohort, in order to further identify pregnant women at an increased risk for preterm delivery. Here, 1,316 samples positive for Ureaplasma parvum were serotyped using a high-resolution melt PCR assay and results were correlated with pregnancy outcome. The results revealed that among Ureaplasma parvum positive samples, serovar 3 was the most common isolate, followed by serovar 6 and serovar 1. A significantly increased risk for spontaneous preterm birth at very low (<32 weeks) and extremely low (<28 weeks) gestational ages was recorded in the group with vaginal Ureaplasma parvum serovar 3 colonization, compared to the control group of pregnant women who were negative for vaginal Ureaplasma spp. colonization. However, an association was neither found for serovar 1 nor serovar 6. Moreover, the combination of vaginal Ureaplasma parvum serovar 3 colonization and diagnosis of bacterial vaginosis in early pregnancy or history of preterm birth further increased the risk of an adverse pregnancy outcome. Hence, it was inferred that colonization with Ureaplasma parvum serovar 3, but not serovar 1 or serovar 6, in early pregnancy is associated with preterm delivery at very and extremely low gestational age. The combination of Ureaplasma parvum serovar 3 colonization and history of preterm birth or bacterial vaginosis further increases the risk for spontaneous preterm birth at low gestational age and may define a target group for therapeutic intervention studies.