Predictors of mode of birth and duration of labour following induction using prostaglandin vaginal gel

Background and aims Using data from a randomised controlled trial (RCT) comparing two policies of prostaglandin ( PGE 2) vaginal gel induction of labour ( IOL ) at term, this study aimed to determine: (i) demographic/clinical factors that predict IOL outcomes; and (ii) clinical characteristic(s) of women who would benefit from a policy of amniotomy once technically possible as opposed to giving more PGE 2. Material and methods Following an initial PGE 2 dose, women were randomised to amniotomy or repeat‐ PGE 2. Using RCT data, two multivariate models were developed, assessing the relationship between demographic/clinical characteristics and the outcomes of caesarean section ( CS ), and vaginal delivery within 24 h ( VD  < 24 h). Regression‐equations were used to predict the likelihood of CS and VD  < 24 h, varying independent predictors from the multivariate analyses. Results Of 245 term women undergoing IOL , 90 had a CS , 155 delivered vaginally and 79 had a VD  < 24 h. Controlling for confounders, nulliparity [adjusted odds ratio ( aOR)  = 3.71 (1.55, 8.88)] and modified Bishop's score ( MBS ) at first review [ aOR  = 0.78 (0.66, 0.92)] were independently associated with CS . Nulliparity [ aOR  = 0.06 (0.02, 0.15)], MBS at first review [ aOR  = 1.66 (1.35, 2.05)], and a policy of early amniotomy [ aOR  = 2.28 (1.04, 5.00)] were associated with VD  < 24 h. Modelling using regression equations, and varying both MBS at first review and parity, there was no scenario where repeat PGE 2 was predicted to be superior to an earlier amniotomy. Conclusions Following IOL using PGE 2 vaginal gel at term, both parity and cervical favourability at first review are associated with CS and VD  < 24 h. All combinations of parity and MBS at first review predicted fewer CS and greater likelihood of VD  < 24 h with a policy of amniotomy once technically possible.