Study designs of evaluations included in the review
To address the question of the benefit and risks of the interventions reviewed, only randomised controlled trials (RCTs) were included.
Specific interventions included in the review
The review considered three categories of intervention: antepartum testing, interventions to induce labour, and no intervention (neither induction nor testing). The review did not examine the role of routine ultrasound in early pregnancy, or interventions performed during labour and delivery to reduce the risks of adverse outcomes of conditions associated with prolonged pregnancy. The tests reviewed were as follows:
tests to determine the risk of stillbirth or compromise related to prolonged gestation included maternal measurement of foetal movement, nonstress test, contraction stress test using either nipple stimulation or oxytocin, amniotic fluid measurements, and Doppler measurements of umbilical or foetal cerebral blood flow;
tests to determine the risk of macrosomia included estimation of foetal weight by maternal judgment, clinical examination and ultrasound;
tests to estimate the likely success of the induction of labour included clinical estimation of cervical ripeness (Bishop's score) and fibronectin.
The testing varied with regard to timing (40, 41 or 42 weeks) and initiation.
The interventions to induce labour were interventions to prevent prolonged pregnancy, and planned induction of labour (41 weeks, 42 weeks, and later than planned date).
The actual agents or interventions employed to induce labour were: amniotomy, castor oil, extra-amniotic saline instillation, relaxin, sweeping of membranes, foley catheter, nipple stimulation, oxytocin, prostaglandins (prostaglandin E2 and misoprostol) and mifepristone.
Participants included in the review
The patient population comprised pregnant women with a single foetus in the vertex position approaching or past the expected date of confinement, who were without any other medical or obstetrical complications, and where the only potential factor increasing the risk of an adverse perinatal or maternal outcome was advanced gestational age. Prior Caesarean section was an exclusion criterion in the majority of primary studies reviewed.
Outcomes assessed in the review
The review's primary outcomes were measures of reduction in maternal or foetal adverse outcomes: maternal mortality, perinatal mortality, maternal morbidity, perinatal morbidity and surrogate measures (neonatal umbilical artery pH, Apgar scores, meconium-stained amniotic fluid, non-reassuring foetal heart rate tracing, Caesarean section rates). Test operating characteristics were also reported in the review.
How were decisions on the relevance of primary studies made?
Two reviewers independently screened references and any disagreements were resolved by consensus.