Induction of labour for post term pregnancy: an observational study.

The aim of the study was to compare the 2 management protocols for postterm pregnancy; elective induction of labour at 42 weeks' gestation and continuing the pregnancy with fetal monitoring while awaiting spontaneous labour. A retrospective observational study compared a cohort of 360 pregnancies where labour was induced with 486 controls. All pregnancies were postterm (>294 days) by an early ultrasound scan. Induction of labour was achieved with either prostaglandin vaginal pessaries or gel or forewater rupture and Syntocinon infusion. The control group consisted of women with postterm pregnancies who were not induced routinely and who usually had twice weekly fetal assessment with cardiotocography and/or ultrasound. Women who had their labour induced differed from those who awaited spontaneous labour. Nulliparas (OR 1.54; 95% CI 1.24-1.83) and married women (OR 1.76; 95% CI 1.45-2.06) were more likely to have their labour induced. There was no association between the type of caregiver and induction of labour. Induction of labour was associated with a reduction in the incidence of normal vaginal delivery (OR 0.63, 95% CI 0.43-0.92) and an increased incidence of operative vaginal delivery (OR 1.46; 95% CI 1.34-2.01). There was no difference in the overall rate of Caesarean section. There was no difference in fetal or neonatal outcomes. Parity had a major influence on delivery outcomes from a policy of induction of labour. Nulliparas in the induced group had worse outcomes with only 43% achieving a normal vaginal delivery (OR 0.78, 95% CI 0.65-0.95). In contrast for multiparas, the induced group had better outcomes with less Caesarean sections (OR 0.88, 95% CI 0.81-0.96). This retrospective observational study of current clinical practice shows that induction of labour for postterm pregnancy appears to be favoured by nulliparous married women. It suggests that induction of labour may improve delivery outcomes for multigravas but has an adverse effect for nulliparas.