Association of bacterial vaginosis, trichomonas vaginalis, and vaginal acidity with outcome of pregnancy.

Background: Bacterial vaginosis and Trichomons vaginalis are believed to be the risk factors for preterm labor birth and preterm prelabor rupture of membranes. The objective of this study was to investigate the association between bacterial vaginosis, T.vaginalis, and vaginal pH with preterm labor birth and preterm prelabor rupture of membranes after excluding other known risk factors.

Methods: In this cohort study, we enrolled 1223 pregnant women with gestational age of 16 - 36 weeks from Amir-Almomenin General Hospital in Semnan, Iran, who had no known medical risk factors for preterm labor birth. Bacterial vaginosis and T.vaginalis were determined on the basis of vaginal pH, saline wet mount, and Amsel tests. The principal outcome was delivery before 37 weeks of gestation and preterm prelabor rupture of membranes.

Results: Bacterial vaginosis and T.vaginalis were detected in 16.0% and 5.5% of these women, respectively. Bacterial vaginosis was positive in 65 (33.1%) patients at 16 - 20 weeks of gestation and in 134 (66.9%) patients at 36 weeks of gestation or during labor (developing preterm labor birth or preterm prelabor rupture of membranes). The frequencies for T.vaginalis were 20 (29.9%) and 47 (70.1%) patients, respectively. All patients with bacterial vaginosis and T.vaginalis had a vaginal pH > or = 5. There was a significant correlation between bacterial vaginosis and vaginal pH > or = 5, with preterm labor birth (OR: 5.99; CI: 3.79 - 9.49) and preterm prelabor rupture of membranes (OR: 2.34; CI: 1.07 - 4.99). Moreover, a significant correlation was found between vaginal pH > or = 5 with preterm labor birth (OR: 5.82; CI: 2.96 - 11.39) and preterm prelabor rupture of membranes (OR: 4.11; CI: 1.62 - 10.12). There was no significant correlation between T.vaginalis with preterm labor birth (OR: 0.73; CI: 0.22 - 2.17) and preterm prelabor rupture of membranes (OR: 1.22; CI: 0.29 - 5.05).

Conclusion: The presence of bacterial vaginosis or vaginal pH > or = 5 at 16 - 36 weeks of gestation is associated with an increased risk of preterm labor birth and preterm prelabor rupture of membranes.