Relationship of vaginal pH and Papanicolaou smear results to vaginal flora and pregnancy outcome.

Prematurity is a major cause of perinatal morbidity. Studies have implicated components of the vaginal flora in the etiology of some cases of preterm birth. Current scoring systems do not include factors which directly reflect the vaginal flora. Since Papanicolaou smears and the vaginal pH may be affected by the vaginal flora and are easy tests to perform, we studied their relationship to vaginal flora and pregnancy outcome. Among 231 patients, those with a vaginal pH greater than or equal to 4.4 were significantly more likely to carry Trichomonas vaginalis (P less than 0.03); Bacteroides species (P less than 0.01), and Mycoplasma hominis (P less than 0.001), and to have premature rupture of the membranes (P less than 0.01), and preterm rupture of the membranes (P less than 0.05). Patients with atypia reported on Papanicolaou smear more frequently carried M. hominis (P less than 0.01), and had premature rupture of the membranes (P less than 0.01). Although the high sensitivity and negative predictive value of those tests may make them useful additions to current scoring systems, their low specificity prevents them from being independent predictors of risk.