Head Circumference and Mid-arm Circumference as Proxy Measures of Gestational Age in Newborns: A Hospital-Based Prospective Observational Study.

Abstract

Background: Accurate assessment of gestational age (GA) guides neonatal care, but first-trimester ultrasonography is often unavailable, and postnatal maturity scoring requires trained staff. Simple anthropometric measurements may serve as practical proxies. This study evaluated the correlation of head circumference (HC) and mid-arm circumference (MAC) with GA and birth weight in newborns. Materials and Methods: This hospital-based prospective observational study enrolled 355 consecutive live-born singleton neonates at a tertiary care hospital in Jaipur, India. GA was assessed using the New Ballard Score (NBS). HC and MAC were measured with a non-stretchable tape at 72 hours of life. Pearson correlation and linear regression were used to assess the relationship of HC and MAC with GA and birth weight. Results: The mean GA was 34.49 ± 3.52 weeks (range 28–41), 238 neonates (67.0%) were preterm, and the mean birth weight was 1915 ± 633 g. Mean HC rose from 24.4 cm at 28 weeks to 33.7 cm at 41 weeks, and mean MAC from 7.9 cm to 9.8 cm. HC correlated strongly with GA (r = 0.865) and birth weight (r = 0.789), whereas MAC showed moderate correlations (r = 0.540 and 0.552, respectively; all p < 0.001). The regression equation GA (weeks) = 3.74 + 1.063 × HC (cm) had a standard error of estimate (SEE) of 1.76 weeks and a mean absolute error (MAE) of 1.42 weeks. Adding MAC improved accuracy modestly (R = 0.884; SEE 1.66 weeks; MAE 1.33 weeks). Conclusion: HC is a strong and simple proxy for GA in newborns, and combining it with MAC modestly improves estimation. These measurements may help classify newborns where ultrasonography or skilled maturity scoring is unavailable, but the equations need external validation.