Reference gender-specific neonatal size at birth growth curves for singleton and twin neonates from North India.

Objectives: To construct reference growth curves for the preterm population from North India and compare it with global charts.

Methods: This prospective study enrolled preterm neonates (23 to 36 weeks) from July 2018 to August 2019 after excluding stillbirths and those with congenital malformations. Anthropometry was performed within 18 hours of birth. Gestation age was assessed by the best estimate of a combination of the last menstrual period, antenatal first-trimester ultrasound, and Expanded New Ballard Score (ENBS). Centile curves were constructed for both genders for twins and singleton neonates separately using the GAMLSS method using R software.

Results: During the study period, of the 14,908 births, 3253 (21.8%) were born preterm. After excluding malformations and stillbirths, 2976 preterm neonates were eligible, out of which anthropometry within 18 hours was done for 2719 neonates. Data was analyzed for 2290 singleton and 414 twin preterm neonates. Smoothed reference growth curves were constructed for all anthropometric parameters for both genders for singleton as well as twin neonates. Indian preterm infants were smaller compared to international standards. The proportion of small for gestational age (SGA) neonates was 23.1% (Fenton's charts) but only 10.9% when the data from the newly constructed chart was used. The concordance with international standards was better for very preterm neonates <32 weeks than moderate and late preterm neonates (32 to 36 weeks).

Conclusions: The reference charts derived from the present study can be used for the North Indian preterm population. The use of western growth charts tends to overestimate the incidence of SGA.