In 5-10% of women their pregnancies continue beyond 294 days (42 completed weeks) and are described as being post-term. Such pregnancies are at increased risk of birth trauma and asphyxia as well as stillbirth and postnatal death.
The risk of pregnancy loss (intrauterine, neonatal and infant death) increases from 1.2 per 1000 ongoing pregnancies at 38 weeks of gestation to 2.4 at 40 weeks and 5.8 at 43 weeks.
In the management of post-term pregnancies, induction of labor compared to expectant management, is associated with a substantial reduction in perinatal mortality. However, approximately 20% of women having induction of labor need an emergency cesarean section for delivery because of failed induction, failure to progress in labor or fetal distress. The rate of cesarean section is dependent on parity, being about 10% for parous women and 30% for nulliparae.