Morphology assessed by transvaginal ultrasonography differs in patients in preterm labor with vs. without bacterial vaginosis

Objective To determine whether cervical morphology in preterm labor patients differs in the presence or absence of bacterial vaginosis. Design Observational study. Subjects One hundred and twelve consecutive patients with objectively confirmed preterm labor admitted to a tertiary care centre were included in the study. Patients with placenta previa, active uterine bleeding or indication for an immediate delivery (e.g. severe pre-eclampsia or suspected fetal asphyxia), or severe fetal anomalies were excluded. Methods Transvaginal ultrasonography was used to measure cervical length and internal of width. Bacterial vaginosis was diagnosed by Gram stain of a vaginal smear. Results A total of 36 patients (32%) had bacterial vaginosis. Cervical length in this group rues shorter than in patients with normal flora (mean 20.4 +/- 7.2 mm vs. 26.4 +/- 6.7 m-m, P = 0.0002), and more patients with bacterial vaginosis had a dilated internal cervical os greater than or equal to 5 mm (67% vs. 30%, P = 0.001). There were no significant differences, however, in preterm delivery rate and birth weight between the two groups; the overall preterm delivery rate was 40%. A cervical length < 25 mm was predictive of preterm delivery (P = 0.001, RR 4.2, 95% Cl 2.8-9.7). Conclusions These data suggest that cervical change in preterm labor is more pronounced in patients with bacterial vaginosis but without a concomitant increase in the risk for preterm delivery. Despite this association, the cervical length measured by transvaginal ultrasonography alone is a useful predictor of preterm delivery, independent of the presence or absence of bacterial vaginosis.