The existing evidence from observational studies links post-term pregnancy with increased perinatal morbidity and mortality. This systematic review (1), summarizes the best available evidence on the effectiveness of interventions aimed at reducing morbidity and mortality associated with post-term pregnancy. The effects of interventions for the induction of labour have been investigated in other Cochrane reviews, but no other review specifically focuses on post-term pregnancy.

This review addresses four essential clinical questions related to post-term pregnancy:

What are the effects of routine early pregnancy ultrasound on the incidence of post-term pregnancy and its outcome?
What are the effects of breast and nipple stimulation on the incidence of post-term delivery?
What are the effects of a policy of labour induction after 41 completed weeks on pregnancy outcome?
What are the effects of complex versus simple fetal monitoring in post-term pregnancy when a selective induction policy is in place?

Routine use of ultrasound in early pregnancy reduced the need for labour induction, and hence the incidence of post-term pregnancy (4 trials with a total of 21776 women; odds ratio (OR) 0.68, 95% confidence interval (CI) 0.57-0.82).
Breast (and nipple) stimulation (not clearly defined in the review) reduced the incidence of post-term pregnancy (2 trials, 355 women; OR 0.52, 95% CI 0.28-0.96).
Routine induction of labour after 41 weeks in uncomplicated pregnancies reduced the risk of perinatal death (13 trials-6073 women; OR 0.23, 95% CI 0.06-0.90)(1). It also reduced the risk of caesarean section (12 trials, 5954 women) and meconium-stained amniotic fluid (9 trials, 5662 women), but the latter two findings need to be interpreted cautiously because of heterogeneity among the trial results.
One randomized trial found that, compared with simple monitoring (cardiotocography and ultrasound measurement of maximum pool depth), complex fetal monitoring (defined as the use of several measures such as computerised cardiotocography, biophysical profile and others) increased the use of labour induction (145 women; OR 2.10, 95% CI 1.10-4.01).

For most of the other interventions studied in the review, the confidence intervals around summary estimates were too broad for the conclusion.

The search was comprehensive and included both published and unpublished trials. The main limitations of the review arise from the nature of the available evidence itself. In the majority of the trials concealment of allocation of the subjects to the intervention group was inadequate or not used at all. The timing of the interventions varied between trials, as did the outcomes for the same interventions. In addition, the definition of post-term pregnancy differed between trials. All these factors rendered the pooled figures in the meta-analysis somewhat meaningless and the conclusions of the analysis difficult to interpret. It can be argued that by including only those studies that had used a standard definition of post-term pregnancy and common outcomes, it may have been possible to obtain more valid conclusions. However, that would have left out too many trials, and as a result the review would have been inconclusive. A sensitivity analysis to establish whether the findings would have been valid had only properly conducted randomized controlled trials (RCT) been included, would have given strength to the conclusions.

This document should be cited as: Luis Gabriel Cuervo. Interventions for preventing or improving the outcome of delivery at or beyond term: RHL commentary (last revised: 6 August 2004). The WHO Reproductive Health Library, No 9, Update Software Ltd, Oxford, 2006. www.rhlibrary.com

Improving the outcome of delivery at or beyond term