Fetal macrosomia : risk factors and outcome. A study of the outcome concerning 100 cases>4500 g

Objective: Because difficult vaginal delivery is more frequent with macrosomic fetuses, some authors recommend routine caesarean section for the delivery of fetuses>4500 g. The purpose of this study was to evaluate the appropriateness of this recommendation, in particular, to analyze maternal and fetal complications according to the mode of delivery. Method: Maternal and neonatal records of 100 infants with weights of at least 4500 g were identified retrospectively from January 1991 to December 1996. Outcome variables included the mode of delivery and the incidence of maternal and perinatal complications. Results: The study sample consisted of 100 infant and mother pairs. Macrosomic fetuses represented 0.95% of all deliveries during this period and only ten were >5000 g. Mean birth weight was 4730 g (maximum, 5780 g). Gestational diabetes was present in nineteen patients. Diabetes was present in three patients. A trial of labour was allowed in 87 women, and elective caesarean delivery was performed in thirteen patients. The overall cesarean rate, including elective caesarean delivery and failed trial of labour, was 36%. Of those undergoing a trial of labour, 73% (64/87) delivered vaginally. Shoulder dystocia occurred fourteen times (22% of vaginal deliveries) and it was the most frequent complication in our series. There were five cases of Erb's palsy, one of which was associated with humeral fracture, and four cases of clavicular fracture. By three months of age, all affected infants were without sequelae. There was no related perinatal mortality and only two cases of birth asphyxia. Maternal complications with vaginal delivery of macrosomic infants included a high incidence of lacerations requiring repair (eleven cases). No complications were noticed in the patients who had a caesarean section. Conclusion: Vaginal delivery is a reasonable alternative to elective cesarean section for infants with estimated birth weights of less than 5000 g and a trial of labour can be offered. For the fetuses with estimated birth weight >5000 g, an elective caesarean section should be recommended, especially in primiparous women.