Vaginal and cervical pH in normal pregnancy and pregnancy complicated by preterm labor.

A prospective study was performed in order to determine vaginal and cervical pH in pregnancy. In normal pregnancy vaginal pH (using a pH meter with connected glass electrode) was found to be between 3.8 and 4.0 (1 SD +/- 0.3) at the introitus, mid-vaginal, and at the anterior and posterior fornix. In patients with preterm labor (n = 50) or prolonged rupture of the membranes (PROM, n = 35) pH was increased significantly to 4.2-4.5 (1 SD +/- 0.7) resp. to 5.2-6.1 (1 SD +/- 0.8). Cervical pH ranges between 6.5 and 7.0 in all groups studied. Elevated pH values are due to disturbed vaginal flora. We recommend vaginal pH measurement for an quick detection of infection in cases with preterm labor and for clarifying PROM in suspicious cases.