Effect of vaginal ph on efficacy of the dinoprostone vaginal insert for cervical ripening/labor induction

Abstract

Objective: To evaluate whether vaginal pH has an effect on the relative efficacy of the dinoprostone vaginal insert (Cervidil) for cervical ripening/labor induction.Methods: Thirty-four gravidas, with an unfavorable cervix and indication for labor induction, were enrolled in this prospective, double-blinded clinical evaluation. Baseline assessment of cervicovaginal pH and Bishop score were made at the time of enrollment by an independent examiner. All patients received Cervidil, 10 mg, intravaginally for 12 hours. Following the initial 12 hours of preinduction, a repeat Bishop score assessment was made by the same initial examiner. Patients not in active labor at 12 hours were placed on a standardized oxytocin induction regimen. Labor was managed by the on-call obstetric team who remained blinded to pH assessment. Clinical outcomes were evaluated. Statistical analyses were made using Students’ t test and linear regression analysis.Results: Average initial vaginal pH was 4.9 ± 0.5 (range 4.0–6.5) for the study cohort. No significant differences were noted between those patients with low vaginal pH (≤4.5), compared with the high pH group (>4.5), with respect to maternal age, parity, gestational age, or initial Bishop score. Similarly, Bishop score change over preinduction interval (3.2 versus 3.3), time to active labor (28.6 versus 24.6), time to complete dilation (31.2 versus 30.2 hr), and time to delivery (33.7 versus 31.4 hr) were not significantly different between the low and high pH groups, respectively. Linear regression analysis revealed no association between vaginal pH and Bishop score change during preinduction interval, time to complete dilation, or time to delivery (P = NS).Conclusion: Vaginal pH does not seem to affect the efficacy of the dinoprostone vaginal insert (Cervidil) for cervical ripening/labor induction.