Study information


INDEX study

Costs and effects of induction of labour versus expectant management in women

with impending post-term pregnancies: the 41 week 42 week dilemma.

Post-term pregnancy is associated with increased perinatal morbidity and mortality and is considered as a high-risk stage which requires specialist surveillance and induction of labour at some stage. However, there is uncertainty in The Netherlands on the policy concerning the timing of induction for post-term pregnancy, leading to practice variation and strong debates between caregivers regarding pros and cons of labour induction for impending post-term pregnancy. To solve this dilemma in the Netherlands we propose a randomised trial to evaluate the effectiveness, costs and cost-effectiveness analysis of policy of labour induction at 41 weeks versus expectant management until 42 weeks in low risk women. We will study adverse perinatal outcome, adverse maternal outcomes, client satisfaction, preferences and costs.

Study design
Multicentre randomised controlled clinical trial with cost-effectiveness analysis.

Study population
Low risk women with a singleton pregnancy and a certain gestational age of 41 (-2/+2) weeks.

Labour induction at 41 weeks, if necessary proceeded by artificial cervical ripening, versus expectant management until 42 weeks.


Outcome measures
The primary outcome will be a composite of perinatal mortality and neonatal morbidity. Adverse perinatal outcomes are defined as, a 5-minute Apgar-score below 7 and/or an arterial pH below 7.05, meconium aspiration syndrome, plexus brachialis injury, intracranial hemorrhage and/or NICU admission.


Secondary outcomes will be maternal outcomes: instrumental delivery (instrumental vaginal delivery, Caesarean section), pain treatment (epidural, remifentanyl, pethidin), hemorrhage and severe perineal injury (third- or fourth-degree perineal tear). Other outcomes are maternal experience of pain, maternal satisfaction and quality of life, client preferences for induction of labour or expectant management, and the extent to which these preferences are influenced by the attributes of obstetric care and socio-demographic factors.

Power/data analysis
Sample size was calculated for non-inferiority testing. Therefore, when the sample size in each group is 900, a two-group large-sample normal approximation test of proportions with a one-sided 0,050 significance level will have 80% power to reject the null hypothesis that labour induction and expectant monitoring are not equivalent (the difference in proportions, is 0,020 or farther from zero in the same direction) in favour of the alternative hypothesis that the proportions in the two groups are equivalent, assuming that the expected difference in proportions is 0,000 and the proportion in the standard group is 0,030. This sample size (900 patients per group) will allow us to have 85% statistical power to detect 2% reduction in the risk of composite perinatal mortality and neonatal morbidity from 3% to 1%.

Economic evaluation
We will collect data alongside the trial to estimate the costs and cost-effectiveness of immediate delivery and expectant management from the societal perspective.

Time schedule
Total study time is 48 months. Preparation time four months, recruitment 38 months, analysis and report six months.


Dr. E. de Miranda, midwife, AMC

Dr. B.W. Mol, gynecologist, AMC


ZonMw 171202008