Body mass index and weight-for-length ratio references for infants born at 33-42 weeks gestation: a new tool for anthropometric assessment

Background & aims

The risk of childhood obesity, an increasingly prevalent problem worldwide, might be predictable by early body mass index measurements. This study sought to develop body mass index and weight-for-length ratio references for infants born at 33–42 weeks gestation and to validate these data against the growth curves of the World Health Organization Multicenter Growth Reference Study.

Methods

Data were collected from the Neonatal Registry of Rabin Medical Center for all healthy singleton babies born live at 33–42 weeks gestation. Crude and smoothed reference tables and graphs for body mass index and weight-for-length ratio by gestational age were created for males and females, separately.

Results

Birth weight, length, and body mass index percentiles for full-term neonates were similar to the World Health Organization study, reinforcing the generalizability of our reference charts for infants born at 33–42 weeks. Cutoff values for small for date (<5th, <10th percentile) and large for date (>85th, >95th percentile) infants differed across gestational ages in both pre-term and full-term infants.

Conclusions

As body proportionality indexes provide an assessment of body mass and fatness relative to length, we suggest that BMI and Wt/L ratio percentiles be added to weight and length growth curves as a routine intrauterine growth assessment at birth.