Can a customized standard for large for gestational age identify women at risk of operative delivery and shoulder dystocia?

OBJECTIVE To determine whether a customized standard for large for gestational age (LGA) identifies undiagnosed women at risk of operative delivery and shoulder dystocia. METHODS We previously generated customized standards from our institution. We compared the baseline maternal characteristics and neonatal outcomes between LGA and non-LGA births, which were classified by both population-based and customized standards. The risk of operative delivery (vacuum delivery or emergent cesarean section) and shoulder dystocia was compared by logistic regression analysis in LGA pregnancies that were identified by a population-based birth weight standard and a customized standard after adjusting for maternal age, parity, body mass index, and neonatal gender. RESULTS Multivariable analysis revealed that the pregnancies identified as LGA by a customized standard were associated with an increased risk of emergent cesarean section [odds ratio (OR), 4.09; 95% confidence interval (CI), 3.00-5.74] and shoulder dystocia (OR, 10.56; 95% CI, 5.52-20.19). However, there was no association between an increased risk of vacuum delivery (OR, 1.45; 95% CI, 0.92-2.30) and pregnancies identified as non-LGA, using both standards. In addition, customized LGA infants were at increased risk of admission to neonatal intensive care unit (OR 1.63; 95% CI, 1.09-2.43). CONCLUSION A customized standard of LGA is useful in identifying previously unrecognized women at risk of emergent cesarean section and shoulder dystocia.