Effect of vaginal pH on efficacy of dinoprostone gel for labour induction: a cross-sectional study.

The purpose of this study was to assess the effect of vaginal pH on efficacy of intracervical dinoprostone gel (PGE2) for labour induction, progression and induction delivery interval. A cross-sectional study was done among 150 term pregnant women planned for induction with unfavourable Bishop's score ≤5. Women were categorised into two groups based on vaginal pH >4.5 and ≤4.5. Induction was done with maximum of three doses of PGE2 based on Bishop's score, followed by oxytocin administration. Failed induction rate was 14.5%. There was no significant association between vaginal pH and Bishop's score change after first gel application. There was no significant difference in failed induction rates, time from induction to active labour as well as induction delivery interval between two groups. Similarly, there was no significant association between oxytocin requirement and mode of delivery with vaginal pH. Intracervical PGE2 is an ideal route, unaffected by vaginal pH.Impact Statement Prostaglandins are organic acids that have diminished solubility in aqueous solution with a low pH. The release of the drug could be altered by the acidity of vagina and this could result in variable clinical response. Vaginal pH may alter the efficacy of intravaginally administered prostaglandins through several potential mechanisms. There was no significant effect of change in vaginal pH on effectiveness of intracervical administered PGE2. There was no significant association between vaginal pH and time from induction to time women is entering into active labour as well as time from induction to delivery. Similarly, there was no significant association between mode of delivery and oxytocin usage with vaginal pH in labour. Intracervical PGE2 is an ideal route, unaffected by vaginal pH. Further randomised studies are required comparing both vaginally administered PG inserts and intracervical PGE2 gels with vaginal and cervical pH, to directly compare their effectiveness in labour induction.