High-density vaginal Ureaplasma urealyticum colonization as a risk factor for chorioamnionitis and preterm delivery.

Background: The aim of this case control study was to investigate the influence of genital Ureaplasma urealyticum colonization on pregnancy outcome.
Methods: One hundred and seventy-two women colonized with Ureaplasma urealyticum without co-existing other infections and 123 women with negative cultures for Ureaplasma urealyticum were enrolled. In a multivariate analysis the influence of quantitative Ureaplasma urealyticum colonization level was determined.
Results: Compared to the negative women increasing colonization with Ureaplasma urealyticum was associated with a significant decrease of birth weight (p<0.0001) and gestational age (p<0.0001) and with a significant increase of chorioamnionitis (p<0.0001) and preterm delivery (p<0.001). In a multivariate analysis high-density Ureaplasma urealyticum colonization was an independent risk factor for chorioamnionitis and preterm delivery, whereas low colonization levels had no effect on an adverse outcome of pregnancy.
Conclusions: The degree of colonization with Ureaplasma urealyticum correlates strongly with an adverse effect on pregnancy outcome.