A normal pregnancy lasts about 40 weeks from the start of the woman's last menstrual period, but anything from 37 to 42 weeks is considered as being within the normal range. Births before 37 weeks are considered preterm because these babies often have breathing difficulties and other problems as some of their organs are not yet fully matured. Births after 42 weeks seem to carry a slightly increased risk for the baby and are associated with a greater number of deaths. No tests can tell if a baby would be better to be left in the womb or labour induced and the baby be born, so arbitrary time limits have been suggested. This review set out to determine if induction of labour at a prespecified time could reduce the risks for the baby. The review found 22 trials involving over 9000 women given induction of labour at various times from 37 weeks to over 42 weeks' gestation; some were quite old trials and the quality was variable. The review grouped the trials by a policy of induction at (1) 37 to 39 weeks, (2) 39 to 40 weeks, (3) < 41 weeks, (4) 41 weeks, and (5) > 41 weeks, compared with a policy of waiting to a later date. There were fewer baby deaths when a labour induction policy was implemented. Such deaths were rare with either policy. Signficantly fewer babies developed meconium aspiration syndrome and fewer caesarean sections were required in the induction group compared with the expectant management group. Women's experiences and opinions about these choices have not been adequately evaluated.
A policy of labour induction compared with expectant management is associated with fewer perinatal deaths and fewer caesarean sections. Some infant morbidities such as meconium aspiration syndrome were also reduced with a policy of post-term labour induction although no significant differences in the rate of NICU admission were seen.
However, the absolute risk of perinatal death is small. Women should be appropriately counselled in order to make an informed choice between scheduled induction for a post-term pregnancy or monitoring without induction (or delayed induction).
As a pregnancy continues beyond term the risks of babies dying inside the womb or in the immediate newborn period increase. Whether a policy of labour induction at a predetermined gestational age can reduce this increased risk is the subject of this review.
To evaluate the benefits and harms of a policy of labour induction at term or post-term compared with awaiting spontaneous labour or later induction of labour.
We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 March 2012).
Randomised controlled trials conducted in women at or beyond term. The eligible trials were those comparing a policy of labour induction with a policy of awaiting spontaneous onset of labour. Cluster-randomised trials and cross-over trials are not included. Quasi-random allocation schemes such as alternation, case record numbers or open random-number lists were not eligible.
Two review authors independently assessed trials for inclusion. Two review authors independently assessed trial quality and extracted data. Data were checked for accuracy. Outcomes are analysed in two main categories: gestational age and cervix status.
We included 22 trials reporting on 9383 women. The trials were generally at moderate risk of bias.
Compared with a policy of expectant management, a policy of labour induction was associated with fewer (all-cause) perinatal deaths: risk ratio (RR) 0.31, 95% confidence interval (CI) 0.12 to 0.88; 17 trials, 7407 women. There was one perinatal death in the labour induction policy group compared with 13 perinatal deaths in the expectant management group. The number needed to treat to benefit (NNTB) with induction of labour in order to prevent one perinatal death was 410 (95% CI 322 to 1492).
For the primary outcome of perinatal death and most other outcomes, no differences between timing of induction subgroups were seen; the majority of trials adopted a policy of induction at 41 completed weeks (287 days) or more.
Fewer babies in the labour induction group had meconium aspiration syndrome (RR 0.50, 95% CI 0.34 to 0.73; eight trials, 2371 infants) compared with a policy of expectant management. There was no statistically significant difference between the rates of neonatal intensive care unit (NICU) admission for induction compared with expectant management (RR 0.90, 95% CI 0.78 to 1.04; 10 trials, 6161 infants). For women in the policy of induction arms of trials, there were significantly fewer caesarean sections compared with expectant management in 21 trials of 8749 women (RR 0.89, 95% CI 0.81 to 0.97).