Objective To observe the association between bishop score (BS) prior to induction of labour (IOL) admission and outcome of delivery.

Design Prospective observational study.

Setting Tertiary referral centre.

Population A total of 605 women with intact membranes induced at term.

Methods BS were determined prior to IOL between April 2009 and March 2010. Labour was induced according to unit guidelines. Receiver operating characteristics curve analysis was used to determine the most discriminatory pre-IOL BS cut-off for determining main outcome measures.

Main outcome measures Caesarean section (CS), caesarean section for failure to progress, operative vaginal delivery for failure to progress.

Results 254 women (42%) were induced for post-dates pregnancy. 214 women (35.4%) were induced for ‘high risk’ indications. The remaining had ‘low risk’ indications. The cut-off pre-IOL BS for determining delivery by CS was <3. The relative risk for delivery by CS was 1.31 (1.01–1.70, p=0.03). The cut-off pre IOL BS for determining delivery by CS for failure to progress was <1 and the relative risk was 2.63 (1.97–3.53, p<0.0001). The cut-off pre IOL BS for determining having operative vaginal delivery for failure to progress was <4 and the relative risk was 2.12 (1.35–3.32, p=0.001). Similar findings were noted in the women induced for post-dates pregnancy and in primigravida and multigravida.

Conclusions Our study showed that operative interventions are significantly more likely to occur at lower BS.