Does a policy of earlier induction affect labour outcomes in women induced for postmaturity? A retrospective analysis in a tertiary hospital in the North of England.

Objectives: to investigate whether a change in the management of postmature pregnancy to earlier induction affects the length of labour and the induction process. Secondly, to assess the feasibility of the research process to inform a future larger study.

Design: a change in management of postmature pregnancy in an NHS hospital in October 2013, from induction at 42 weeks gestation to induction between 41-42 weeks, provided an opportunity to conduct a retrospective analysis. Pre-existing data from the maternity database and casenotes were collected and primary outcomes analysed using the Mann-Whitney test and the Hodges-Lehman confidence interval for differences in medians.

Setting: a large city based tertiary referral hospital in the North of England.

Participants: 125 women induced before the change in policy were compared with 309 women induced after the change.

Measurements: primary outcomes were length of 1st and 2nd stage of labour, overall length of labour, length of induction to established labour and length of induction to birth.

Findings: the median overall length of labour for women induced at 42 weeks was 6.5hours, while for women induced at 41-42 weeks this was 5.2hours. The difference was not statistically significant (p=0.15, 95% CI for median difference -0.27 to 1.93hours) with a small effect size (Pearson's r=-0.08). The median length of induction to birth was 13.6hours for women induced at 42 weeks and 16.5hours for women induced at 41-42 weeks. This difference was also not statistically significant (p=0.14, 95% CI for median difference -7.25 to 1.20hours) with a small effect size (Pearson's r=-0.13).

Key Conclusions And Implications For Practice: This study demonstrated no statistically significant differences in length of labour and induction following a change in the management of postmature pregnancy to earlier induction. A large study is needed to establish definitively the effects of earlier induction on labour outcomes.