Growth Curves for Infants Born at Military Hospitals: Redefining Standards † 1246

Current standards used to assess specific anthropometric measures (weight[W], length [L], and occipitofrontal circumference [OFC]) in infants employ the use of growth curves established by Lubchenco et al in 1967. These curves are used to classify an infant as small, appropriate, or large-for-gestational age (SGA, AGA, LGA respectively). These classifications can bear significant implications for the newborn (further work-up for SGA and LGA infants) and parents (prognosis for SGA and LGA infants). We have observed a high percentage of newborns with birthweight >4000 gms (11.8%) and >4500gms(2.8%) in our population. Our aim was to compare measurements of W, L, and OFC in a population of infants born at military hospitals (MH) with Lubchenco. W(kg), L (cm), and OFC (cm) were compiled from 6422 infants born at two MH from 1992-1995. Infants were grouped by gestational age (GA) and gender. The 10^th, 25^th, 50^th, 75^th, and 90^th percentiles were calculated at each GA for all infants. 95% confidence intervals (CI) were calculated for each parameter at each GA and medians were compared to medians from Lubchenco. For W, Lubchenco medians fell outside the 95% CI for infants at 24,25, and 27 weeks and were larger than infants born at these GA at MH. For OFC, Lubchenco medians fell outside the 95% CI for infants at 29-31 weeks and were also larger than infants born at these GA at MH. For L, Lubchenco medians fell within our 95% CI up to 35 weeks. However, for W, Lubchenco medians also fell outside the 95% CI for infants at 39-42 weeks and were smaller than 39-42 week infants born at MH. For L, Lubchenco medians diverged outside our 95% CI for infants at 36-42 weeks and were smaller compared to 36-42 week infants born at MH. OFC had similar trends with Lubchenco medians falling outside our 95% CI for infants at 37-42 weeks and were also smaller compared to the similar group at MH. We conclude, in general, infants born less than 30 weeks at these MH have smaller OFC's and weigh less compared to Lubchenco, but infants near term gestation are larger in OFC, L, and W compared to previous standards. We speculate that differences in the study population, environmental factors, and maternal factors play a role in the anthropometric differences observed.