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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 highbirth-weight fetus.

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