Fetal macrosomia: does antenatal prediction affect delivery route and birth outcome?

Our purpose was to determine whether clinical or ultrasonographic prediction of fetal macrosomia influences subsequent delivery route and birth outcome in a clinical setting where macrosomia is not considered an indication for cesarean delivery.

The hospital records of 504 patients delivered of infants weighing > or = 4200 gm between October 1989 and March 1994 were reviewed. Statistical comparisons were made between patients in whom fetal macrosomia was predicted before delivery (n = 102) and those in whom it was not (n = 402). Cesarean delivery, shoulder dystocia, and birth trauma rates were the variables of interest.

Cesarean sections were performed in 52% of the "predicted" group deliveries and in 30% of the "not predicted" group (p < 0.01). The increased cesarean delivery rate in the predicted group appeared to be related to an increased incidence of labor inductions (42.5% vs 26.6%, p = 0.005) and a greater proportion of failed inductions. The proportion of patients delivered by cesarean section without a trial of labor was similar in the predicted and not predicted groups (14.7% vs 10.2%, p = 0.21). There was no significant differences in the incidence of shoulder dystocia or the occurrence of birth trauma.

The antenatal prediction of fetal macrosomia is associated with a marked increase in cesarean deliveries without a significant reduction in the incidence of shoulder dystocia or fetal injury. Ultrasonography and labor induction for patients at risk for fetal macrosomia should be discouraged.