Novel noninvasive anthropometric measure in preterm and full-term infants: normative values for waist circumference:length ratio at birth

BACKGROUND: Waist circumference:length ratio (WLR) and ponderal index (PI) appear to be useful markers of visceral and total adiposity, respectively. However, there are no normative birth data across the full range of gestational ages. METHODS: In this retrospective cohort study of 500 preterm and 1,426 full-term infants, born in 1998 and 2008 at three military hospitals, the percentile growth curves for WLR and PI were calculated. There were no sex differences, and results were combined to obtain values from 26 to 42 wk gestation. RESULTS: Between 26 and 42 wk gestation, median birth WLR increased from 0.55 to 0.62, and median PI increased from 21.1 to 25.6. The adjusted mean WLR at birth among infants born <34 wk increased from 0.55 in 1998 to 0.58 in 2008 (P = 0.048), suggesting that early-preterm infants born in 2008 had greater abdominal adiposity than those born in 1998. CONCLUSION: We report normative birth data for WLR and PI in preterm and full-term infants by gestational age and sex. WLR and PI may be useful as clinical markers of visceral and overall adiposity. In conjunction with other anthropometric measures, WLR and PI may be useful to monitor postnatal nutrition and growth and assess risk for later obesity and cardiometabolic disorders.