Specific weight formula for fetuses with abdominal wall defects

Objectives To develop and to evaluate a specific sonographic weight formula for fetuses with abdominal wall defects. Methods For formula finding, 380 preterm singleton pregnancies without fetal anomalies were included. Ultrasound examinations with complete biometric parameters were performed within 7 days before delivery. Stepwise regression analysis was carried out with birth weight as the dependent variable and sonographic parameters (abdominal measurements not included) as independent variables to obtain the best-fit formula. The new equation was evaluated in a group of 97 fetuses with either gastroschisis or omphalocele. Results In the evaluation group, the mean (SD) percentage error of the new equation was -0.84 (12.03), showing no systematic bias. The mean absolute percentage error was 9.29. The new specific method provided significantly greater accuracy than commonly used formulae. Conclusions This specific weight formula for fetuses with abdominal wall defects is an accurate method of estimating fetal weight. Copyright (c) 2008 ISUOG. Published by John Wiley & Sons, Ltd.