Do Specific Weight Formulas for Fetuses = 1500 g Really Improve Weight Estimation?
PURPOSE: In addition to gestational age, fetal weight is an important predictive parameter for neonatal morbidity and mortality in very small fetuses. In order to improve weight estimation, specific weight formulas for fetuses under 1500 g have been introduced by several authors. The aim of the present study was therefore to compare specific weight equations for fetuses under 1500 g with widely used methods that were designed for the whole fetal weight range. MATERIALS AND METHODS: 459 pregnancies were included in order to evaluate six widely used formulas and four formulas specifically designed for very small fetuses. The inclusion criteria were a singleton pregnancy, birth weight equal to or less than 1500 g, ultrasound examination with complete biometric parameters during the 7 days prior to delivery, and an absence of structural or chromosomal malformations. RESULTS: All formulas, except the Hadlock equations, demonstrated a significant systematic error. Regarding the random error,