Association of head circumference and shoulder dystocia in macrosomic neonates.

To determine whether asymmetric macrosomia (disproportionately large body size in comparison to head circumference) could be demonstrated in a population of infants suffering shoulder dystocia during delivery relative to those that did not suffer from shoulder dystocia. A case-control study was conducted as a retrospective chart review over 3 years at a large maternity hospital in an urban setting. Among infants over 4,000 g, those that suffered from shoulder dystocia during delivery had a smaller mean head circumference than infants of a similar size that did not suffer from shoulder dystocia. A statistically significant difference was also present when cases of documented gestational diabetes were excluded. Asymmetric macrosomia is more likely to be present in a population of infants who suffered shoulder dystocia during delivery. This knowledge could be used in designing tools to predict which pregnancies are at highest risk for shoulder dystocia during delivery.