Anthropometric Charts for Infants Born Between 22 and 29 Weeks' Gestation.

Objectives: Using a large, racially diverse US dataset, we aimed primarily to: (1) fit and validate sex-specific birth weight and head circumference for gestational age charts for infants born at 22 to 29 weeks' gestation; and (2) fit race-specific birth weight and head circumference for gestational age charts.

Methods: We used data collected between 2006 and 2014 on 183 243 singleton infants without congenital malformations with gestational age between 22 weeks, 0 days and 29 weeks, 6 days from 852 US members of the Vermont Oxford Network. For the sex-specific charts, the final sample size included 156 587 infants who survived hospital discharge. From these 156 587, we abstracted a subset of 47 005 infants to fit sex-specific charts separately for white, black, and Asian infants. For all charts, we applied quantile regression models to predict infants' birth weight and head circumference percentiles from gestational age expressed in days.

Results: We successfully validated the overall sex-specific charts. Over most of the gestational age range, black infants, either girls or boys, had the lowest predicted birth weight as compared with white and Asian infants for many percentiles.

Conclusions: We fitted and validated new sex-specific charts using a recent, large, and racially diverse dataset. Future steps include using these charts to examine associations of weight and head circumference at birth with mortality and morbidity.