Should cervical favourability play a role in the decision for labour induction in gestational hypertension or mild pre-eclampsia at term? An exploratory analysis of the HYPITAT trial

Objective To examine whether cervical favourability (measured by cervical length and the Bishop score) should inform obstetricians' decision regarding labour induction for women with gestational hypertension or mild pre-eclampsia at term. Design A post hoc analysis of the Hypertension and Pre-eclampsia Intervention Trial At Term (HYPITAT). Setting Obstetric departments of six university and 32 teaching and district hospitals in the Netherlands. Population A total of 756 women diagnosed with gestational hypertension or pre-eclampsia between 36 + 0 and 41 + 0 weeks of gestation randomly allocated to induction of labour or expectant management. Methods Data were analysed using logistic regression modelling. Main outcome measures The occurrence of a high-risk maternal situation defined as either maternal complications or progression to severe disease. Secondary outcomes were caesarean delivery and adverse neonatal outcomes. Results The superiority of labour induction in preventing high-risk situations in women with gestational hypertension or mild pre-eclampsia at term varied significantly according to cervical favourability. In women who were managed expectantly, the longer the cervix the higher the risk of developing maternal high-risk situations, whereas in women in whom labour was induced, cervical length was not associated with a higher probability of maternal high-risk situations (test of interaction P = 0.03). Similarly, the beneficial effect of labour induction on reducing the caesarean section rate was stronger in women with an unfavourable cervix. Conclusion Against widely held opinion, our exploratory analysis showed that women with gestational hypertension or mild pre-eclampsia at term who have an unfavourable cervix benefited more from labour induction than other women. Trial registration The trial has been registered in the clinical trial register as ISRCTN08132825.