Prolonged pregnancy: is induction of labour indicated? A prospective study.

A prospective controlled study of 2000 patients to determine the incidence of postmaturity and the effect of a policy of non-induction of labour in prolonged pregnancy is reported. 'Certain postmaturity' was identified in 4% of the patients and was associated with an increased incidence of babies with Apgar scores of less than 5 at 1 min; induction of labour at 42 weeks gestation did not affect the neonatal outcome compared with that in patients allowed to go into spontaneous labour. Induction of labour in patients designated as 'certain postmature' and 'uncertain postmature' reduced the number of vaginal deliveries and increased the caesarean section rate from 9.6 to 26.7 and from 2.2 to 31.2% respectively. The failure to improve the perinatal outcome does not support or justify induction of labour for uncomplicated postmaturity.