Macrosomia: mode of delivery and pregnancy outcome

Objective. To assess associations between birthweight and selected adverse outcomes in vaginal and cesarean deliveries and to clarify to which extent macrosomic births are delivered by cesarean section or are centralized to larger maternity units. Design. Cohort study. Setting. National study based on the Medical Birth Registry of Norway. Population. All births in Norway for the duration 1999-2005 comprising 304,968 vaginal and 47,702 cesarean deliveries. Methods. Rates of adverse pregnancy outcomes by birthweight in vaginal and cesarean deliveries were compared by odds ratios (ORs) obtained in logistic regression analysis with birthweight 2,500-3,999 g as the reference and adjusted for maternal age, birth order and size of maternity unit. Main outcome measures. Analgesia, interventions, complications and neonatal outcomes. Results. For all the adverse outcomes, the ORs increased continuously from the reference group up to >= 5,000 g in which the highest adjusted ORs were observed for shoulder dystocia [64.2 (confidence interval 55.7-74.0)] and plexus injuries [47.7 (confidence interval 35.7-62.4)]. The proportion of adverse outcomes attributable to macrosomia (birthweight >= 4,500 g) ranged from 56.8% of all shoulder dystocia cases to 0.5% of all stillbirths. Macrosomic births were not centralized to larger maternity units and planned cesarean delivery was not more frequent in macrosomic births. Conclusions. Macrosomic births involved excess risks of a series of adverse pregnancy outcomes, the births were not centralized to larger maternity units and planned cesarean section was not more frequent in macrosomic births.