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 os 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 was shorter than in patients with normal flora (mean 20.4 +/- 7.2 mm vs. 26.4 +/- 6.7 mm; P = 0.0002), and more patients with bacterial vaginosis had a dilated internal cervical os > or = 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% CI 1.8-9.7).
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.