Longitudinal trajectory of bacterial vaginosis during pregnancy.

Objective: This study was undertaken to characterize the course of bacterial vaginosis in pregnancy and to discern the bacterial morphotypes responsible for infection.
Study Design: Vaginal secretions were obtained in each trimester of pregnancy and were evaluated for bacterial vaginosis by Gram stain, categorized as normal or any of the following: Lactobacillus deficient, Gardnerella, Bacteroides, or Mobiluncus positive and by Nugent score. Results were evaluated for trends of bacterial vaginosis and Gram stain over pregnancy.
Results: One hundred forty-eight women were evaluated. Seventy-one women (48%) were bacterial vaginosis negative in all trimesters, compared with 14 (9.4%) who were positive throughout pregnancy. Among the 14 women who remained bacterial vaginosis positive, Gram stain findings were Gardnerella+Bacteroides+Lactobacillus, with approximately 50% harboring Mobiluncus. Few women become bacterial vaginosis positive as pregnancy progressed (6.1%). With each increasing week of pregnancy, the risk of becoming bacterial vaginosis positive decreased (0.93: 0.91-0.95; P < .001).
Conclusion: In this population, the majority of pregnant women trend toward bacterial vaginosis negative status. Few women are bacterial vaginosis positive across their pregnancy.