Estimated Fetal Weight: Comparison of Clinical Versus Ultrasound Estimate

Abstract

Background: Accurate estimation of fetal weight is of paramount importance in the management of labour and delivery.Methods: This was a cross sectional study conducted over a period of 6 months in a tertiary care teaching hospital. All singleton term mothers with cephalic presentation and intact membranes with ultrasound examination done within a week were included in the study. IUFD, multiple gestation, malpresentation, diagnosed oligohydramnios or polyhydramnios, pelvic and or abdominal masses, and current weight more than 80 Kgs were excluded from the study. Expected fetal weight was estimated by clinical method (Johnson's formula), which was compared with Ultrasound weight estimation (Hadlock method) and actual birth weight. Results:The estimated mean birth weight by clinical method was 3492.75±393.16g, by Ultrasound was 3230.02±407.22g and actual mean birth weight was 3236.32±472.87g. The estimated birth weight by ultrasonographic method showed slightly stronger positive correlation (r=0.54; p<0.001) with actual birth weight as compared to the clinical method (r=0.44; p<0.001). The error of estimation of weight by clinical method showed significant negative correlation (r=-0.24; p=0.01) with gestational age, however ultrasonographic method did not show significant correlation (r= +0.045; p=0.64). The sensitivity and specificity of clinical method and ultrasonographic method for identifying fetal birth weight above 3500 gm was 69.23; 65.67% and 46.15; 80.60%, respectively. Conclusions:Ultrasound was more reliable method to establish fetal weight at term and more consistent in various period of gestations. Clinical method can be reliably used to screen large babies in centers where ultrasound has limited availability.

Correlation of ultrasonographic estimated fetal weight with actual birth weight at a rural setting

“…Results showed that the difference of fetal weight estimated by shepherd's method is closer to the actual compared with Hadlock method. These findings are consistent with the results of studies done previously by Ratanasiri T et al, Eze CU et al, Joshi A et al, Yadav R and Lima AMH et al [12][13][14][15][16] By using paired sample correlation for Estimated fetal weight, the correlation between estimated fetal weight by Hadlock and actual fetal weight is greater than the correlation between estimated fetal weight by shepherd's and actual fetal weight, this signifies that the estimated fetal weight by Hadlock is better than estimated fetal weight by shepherd's. From standard deviation, the estimation by Hadlock is centralized to the mean more than that estimated by Shephard's.…”

Johnson’s formula to compare fetal weight with actual birth weight

“…However, the correlation was weak for babies less than 2.5 Kg and more than 4.0 kg. Joshi et al 35 in their study also observed strong positive correlation "(p<0.001) between actual birth weight in comparison to the clinical" approach.…”

Clinical Estimation of Fetal Weight with Reference to Johnson’s Formula: An Alternative Solution Adjacent to Sonographic Estimation of Fetal Weight

“…During the last decade, estimated fetal weight has been incorporated into the standard routine ante-partum evaluation of high risk pregnancies and deliveries both within Nepal and across the world. 6,17,18 A lot of work has been carried out to find accurate methods to estimate of fetal size and weight in utero. They include clinical and ultrasound estimations.…”

“…They include clinical and ultrasound estimations. [9][10][11]17,18 We found the accuracy of estimation of fetal weight by Johnson's formula to be within 20% in 70% of these macrosomic babies and by ultrasound to be within 40% in 70% of these cases. In a study done by Sharma et al showed that clinical estimation was more accurate in determining fetal weight, particularly in macrosomic babies and those diagnosed GDM cases, with the estimation of fetal weight within 20% of 60% of their study population.…”