Effect of labour induction on rates of stillbirth and cesarean section in post-term pregnancies

Background: Meta-analyses of randomized controlled trials suggest that elec tive induction of labour at 41 weeks' gestation, compared with expectant ma nagement with selective labour induction, is associated with fewer perinata l deaths and no increase in the cesarean section rate. The authors studied the changes over time in the rates of labour induction in post-term pregnan cies in Canada and examined the effects on the rates of stillbirth and cesa rean section. Methods: Changes in the proportion of total births at 41 weeks' and at 42 o r more weeks' gestation, and in the rate of stillbirths at 41 or more weeks ' (versus 40 weeks') gestation in Canada between 1980 and 1995 were determi ned using data from Statistics Canada. Changes in the rates of labour induc tion and cesarean section were determined using data from hospital and prov incial sources. Results: There was a marked increase in the proportion of births at 41 week s' gestation (from 11.9% in 1980 to 16.3% in 1995) and a marked decrease in the proportion at 42 or more weeks (from 7.1% in 1980 to 2.9% in 1995). Th e rate of stillbirths among deliveries at 41 or more weeks' gestation decre ased significantly, from 2.8 per 1000 total births in 1980 to 0.9 per 1000 total births in 1995 (p < 0.001). The stillbirth rate also decreased signif icantly among births at 40 weeks' gestation, from 1.8 per 1000 total births in 1980 to 1.1 per 1000 total births in 1995 (p < 0.001). The magnitude of the decrease in the stillbirth rate at 41 or more weeks' gestation was gre ater than that at 40 weeks' gestation (p < 0.001). All hospital and provinc ial sources of data indicated that the rate of labour induction increased s ignificantly between 1980 and 1995 among women delivering at 41 or more wee ks' gestation. The associated;changes in rates of cesarean section were var iable. Interpretation: Between 1980 and 1995 clinical practice for the management of post-term pregnancy changed in Canada. The increased rate of labour indu ction at 41 or more weeks' gestation may have contributed to the decreased stillbirth rate but it had no convincing influence either way on the cesare an section rate.