[Accuracy of ultrasound estimated fetal weight performed by OB-Gyn residents at due date].

OBJECTIVES: The aim of this study was to evaluate the accuracy of ultrasound fetal weight prediction at due date and to find parameters that may affect this prediction.

PATIENTS AND METHODS: We retrospectively studied 201 patients at due date in a university hospital in 2006, the fetal weight estimation being performed by Obstetric-gynecology (OB-Gyn). Estimated fetal weight was calculated with the Hadlock's formula, including biparietal diameter, cephalic circumference, abdominal perimeter and femoral length and was compared with birth weight.

RESULTS: The mean birth weight was 3561+/-415 g. The mean absolute weight difference was 261+/-190 g (absolute range: 0 to 1183 g, actual range: -935 to 1183 g). Body mass index>30 kg/m(2) was associated with greater fetal weight inaccuracy (p=0,013). Fetal weight estimation was not influenced by fetal macrosomia, oligoanamnios or maternal weight gain during pregnancy.

DISCUSSION AND CONCLUSION: The sonographic estimated fetal weight and birth weight are correlated with a mean absolute percentage error of 7%. However, clinicians should be aware of the risk of inaccuracy in obese women.