Birth Body Mass Index (Bmi) of Late Preterm and Early-Term Newborns

Abstract

Introduction: the nutritional status and the growth achieved by the newborn until birth have been used as a marker/indicator of early risks of morbidity and mortality. Even though BMI is a good marker of adiposity and is commonly used in older children and adults, there are still gaps in knowledge and there are few studies on the behavior of BMI according to gestational age. Objective: to analyze the Body Mass Index (BMI) at the birth of late preterm newborns (34th to 36th week of gestational age) and early-term newborns (37th to 38th week of gestational age) and according to gestational age. Methods: this is a descriptive, analytical, and quantitative study with 2,486 newborns, developed from the project’s database “Biometric characteristics at birth, of young adult women’s babies, in a municipality with a high human development index.” After collection, data consistency was verified. The analysis evaluated measures of central tendency and dispersion of values, in addition to correlations and regressions of their evolution according to gestational age. Results: BMI scores Z distribution wasn’t different between male and female late preterm newborns as in early-term newborns. The same was observed concerning gestational ages. In terms of absolute BMI values, it was observed that late preterm newborns had a lower BMI (12.6 kg/m2) than early-term newborns (13.6 kg/m2). However, considering their gestational age, late preterm newborns were proportionally bigger than early-term newborns. A proportionally higher rate of BMI growth was observed in late preterm newborns, with a tendency to slow down in early-term newborns. As for weight gain, from the 37th week of gestational age, it tends to decrease compared to the reference values. Conclusion: Regarding the BMI reference values, early-term and late-preterm newborns are equivalent. Late-preterm newborns have the same BMI Z-scores as reference values as early-term newborns.