Validity of the normal fetal weight curve estimated by ultrasound for diagnosis of neonatal weight - Revista Brasileira de Ginecologia e Obstetrícia

PURPOSE: tocompare the ultrasound estimation of fetal weight (EFW) with neonatal weight and to evaluate the performance of the normal EFW curve according to gestational age for the diagnosis of fetal/neonatal weight deviation and associated factors. METHODS: one hundred and eighty-six pregnant women who delivered at the institution from November 1998 to January 2000 and who had one ultra-sonographic evaluation performed until three days prior to delivery with estimation of the amniotic fluid index were included. EFW was calculated and classified in to small for gestational age (SGA), adequate for gestational age (AGA) and large for gestational age (LGA) through the normal EFW curve for this population. Neonatal weight was similarly classified. The variability of the measures and the degree of linear correlation between EFW and neonatal weight, as well as sensitivity, specificity and predictive values for the use of the normal EFW curve in the diagnosis of neonatal weight deviations were calculated. RESULTS: the difference between EFW and neonatal weight ranged from -540 to +594 g, with a mean of +46.9 g, and the two measures presented a linear correlation coefficient of 0.94. The normal EFW curve had a sensitivity of 100% and specificity of 90.5% in detecting SGA neonates and of 94.4 and 92.8%, respectively, in detecting LGA; however, the predictive positive values were low for both conditions. CONCLUSIONS:ultrasound EFW was in agreement with the neonatal weight, with a mean overweight of approximately 47 g, and its normal curve showed a good performance in the screening of SGA and LGA neonates.