Accuracy of Ultrasound Estimation of Fetal Weight by Obstetrics and Gynaecology Residents and Maternal-fetal Medicine Subspecialists

Abstract

Objectives: This study was undertaken to assess the accuracy of sonographic estimations of fetal weight performed by maternal-fetal medicine subspecialists and obstetrics and gynaecology residents. Methods: Retrospective data were retrieved between May and December 2011 for all women with  ingleton pregnancies of more than 24 weeks who had an ultrasound examination within 1 week of delivery. Sonographic parameters including the bi-parietal diameter, abdominal circumference, and  emur length were measured according to the established criteria, and referred to the revised reference  harts of fetal biometry. The estimated fetal weights were calculated using the Hadlock formula and compared with the infants’ actual birth weights by using statistical analysis.
Results: The mean absolute errors ± standard deviation of ultrasound fetal weight estimations performed by maternal-fetal medicine subspecialists and obstetrics and gynaecology residents were 5.89% ± 5.10% and 7.77% ± 5.72%, respectively (p=0.03). The percentage of correctly estimated fetal  eights (defined as <10% difference from the actual birth weight) was significantly different between the maternal-fetal medicine subspecialists and obstetrics and gynaecology residents at 79.3% and 65.4%,  espectively (p=0.01).
Conclusion: The accuracy demonstrated by the obstetrics and gynaecology residents was comparable to  some of the published studies. The maternal-fetal medicine subspecialists performed better in sonographic estimation of fetal weight than did the obstetrics and gynaecology residents. However, one in five of the estimates made by the maternal-fetal medicine subspecialists was more than 10%  difference from the actual birth weight of the infant.