A customized standard of large size for gestational age to predict intrapartum morbidity.

OBJECTIVE

The purpose of this study was to determine whether a customized standard of large-for-gestational age (LGA) identifies pregnancies with increased perinatal risk.

STUDY

DESIGN

We evaluated 7510 estimates of fetal weight to generate a fetal growth curve. Next, we analyzed the gestational age at delivery, physiologic and pathological variables from 5072 pregnancies to predict birthweight, and calculated a customized ideal birthweight and cutoff for LGA. In a separate analysis of 32,271 pregnancies, rates of macrosomia-related adverse outcomes were compared in pregnancies that had been identified as LGA by a customized standard (LGA(cust)) and those pregnancies that had been identified as LGA or macrosomic by conventional standards.

RESULTS

LGA(cust) pregnancies carried increased risk of shoulder dystocia, third- or fourth-degree laceration, and cephalopelvic disproportion. LGA(cust) pregnancies that did not meet conventional criteria for LGA/macrosomia were at increased risk of all measured outcomes.

CONCLUSION

A customized standard of LGA identifies a previously unrecognized population that is at increased risk of perinatal morbidity.