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.