Midtrimester bacterial vaginosis and cervical length in women at risk for preterm birth

Objective: The purpose of this study was to estimate the effect of bacterial vaginosis on midtrimester cervical length in women at increased risk for recurrent spontaneous preterm birth.

Study design: We conducted a secondary analysis of prerandomization data from a multicenter trial of ultrasound-indicated cerclage. Women with previous spontaneous preterm birth at <34 weeks' gestation underwent initial cervical length assessment and vaginal fluid collection at 16-21 weeks 6 days gestation. Gram stains were scored with Nugent criteria. With serial scans, the shortest cervical length was observed.

Results: Records for 949 women had complete data. In unadjusted regression models, Nugent score (P = .003) and vaginal fluid pH (P = .008) were related inversely to cervical length. Women with bacterial vaginosis based on Nugent score ≥7 (P = .04) or pH ≥5 (P = .016) had significantly lower cervical length than unaffected women; however, all of these effects were null after covariate adjustment.

Conclusion: Nugent score, pH level, and bacterial vaginosis are associated inversely with cervical length; however, these relationships become null after adjustment for relevant covariates.