Clinical and ultrasound estimation of birth weight prior to induction of labor at term

Authors


Abstract

Objectives

To assess and compare the accuracy of clinical and sonographic fetal weight estimation in predicting birth weight prior to induction of labor.

Methods

In a prospective study of 262 women immediately prior to induction of labor, the fetal weight was estimated clinically by both the doctor (DR EFW) and the woman herself (WM EFW). A transabdominal scan was then performed to estimate the fetal weight sonographically using two different formulae—Shepard (SHEP EFW) and Hadlock (HAD EFW). The four estimated fetal weights were compared with the actual birth weight.

Results

The mean percentage error was − 1.9 ± 9.3% for DR EFW, − 3.4 ± 12.6% for WM EFW, − 2.3 ± 11.6% for SHEP EFW and − 7.6 ± 10.6% for HAD EFW. All four EFWs were significantly different from birth weight (t = − 4.7, − 5.5, − 3.5 and − 11.4, respectively, all P < 0.01). The corresponding proportion of the EFWs which were within 10% of birth weight were 71%, 59%, 62% and 42%, respectively. The sensitivity and specificity of detecting a fetus weighing < 3000 g were 56% and 98% for DR EFW, 90% and 89% for WM EFW, 93% and 83% for SHEP EFW and 100% and 76% for HAD EFW. The corresponding values for detecting a fetus weighing > 4000 g were 16% and 99%, 29% and 96%, 48% and 92% and 40% and 94%, respectively.

Conclusions

Although, in general, clinical estimates of birth weight perform favorably compared with ultrasonographic estimates, ultrasound immediately prior to labor is more accurate at predicting the low- or high-birth-weight fetus. Copyright © 2007 ISUOG. Published by John Wiley & Sons, Ltd.

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