Estimation of Fetal Weight in Utero by Ultrasound

Abstract

In order to find the best fitting regression equation to estimate fetal weight in utero using ultrasonic fetal parameters i.e. biparietal diameter (BPD), ab dominal circumference(AC), and femur length(FL), ultrasonic measurements were carried out among 162 fetuses at Maharaj Nakorn Chiang Mai Hospital between February 1990 and June 1991. The ultrasonic measurements were conducted within 24 hours before delivery. The fetal weight was obtained from neonatal records. The data was analysed by using stepwise multiple linear regression analysis. It was found that the best fitting equation was: Log 10 (EFW) = 1.85479 + 0.09008(BPD) + 0.02466(AC) [coefficient of determination(R2) = 0.939, multiple R = 0.969, p<0.000). The absolute mean error - SD(%) calculated by (estimated fetal weight - actual fetal weight / actual weight x 100] for the equation derived in this study group was 6.980 = 7.017. The absolute mean error SD (%) for Shepard's equa tion applied to the fetal parameters from this study was 6.885 : 6.397. Further more, a table of predicted fetal weight at various lengths of BPD and AC was prepared with computer assistance to read the estimated fetal weight directly (Thai J Obstet Gynaecol 1992;4: 15-22.)