Incidence of persistent birth injury in macrosomic infants: association with mode of delivery.

OBJECTIVE: Our purpose was to determine the incidence of birth injury in a cohort of macrosomic infants (birth weight >4000 gm) and analyze the association between persistent injury and delivery method.

STUDY DESIGN: Deliveries of 2924 macrosomic infants were reviewed. Outcomes were compared with those of 16,711 infants with birth weights between 3000 and 3999 gm.

RESULTS: Macrosomic infants had a sixfold increase in significant injury relative to controls (relative risk 6.7,95% confidence interval 6.5 to 6.9). Risk of trauma correlated with delivery mode: forceps were associated with a fourfold risk of clinically persistent findings compared with spontaneous vaginal delivery or cesarean section. However, the overall incidence of persistent cases remained low (0.3%); a policy of elective cesarean section for macrosomia would necessitate 148 to 258 cesarean sections to prevent a single persistent injury. Avoidance of operative vaginal delivery would require 50 to 99 cesarean sections per injury prevented.

CONCLUSIONS: These findings support a trial of labor and judicious operative vaginal delivery for macrosomic infants.