chapter  11
Labour, including induction – normal/abnormal
Pages 16

The rationale for induction at or before 42 weeks’ gestation is the increased risk of stillbirth and complications that may result in perinatal death, including a failing placenta. Perinatal mortality falls to a trough between 38 and 40 weeks’ gestation and then starts to rise after 41 weeks’ gestation. The risk of stillbirth is approximately 1:3000 at 37 weeks and falls to 1:1000 at 42 weeks and then to 1:500 at 43 weeks. Induction at or before 42 weeks’ gestation is therefore said to be at the time when the perinatal mortality is beginning to rise, but is not high enough to warrant immediate delivery. A randomised trial by Cardozo et al. (1986) demonstrated that, in order to reduce one perinatal death at or before 42 weeks’ gestation, at least 500 inductions have to be performed.