Accuracy of sonographic fetal weight estimation prior to delivery in a Chinese han population.

OBJECTIVE

To compare the sonographic-estimated fetal weights (EFW) calculated with the Hadlock formula and with the Woo formula in a group of Chinese pregnant women.

METHODS

We prospectively recruited term pregnancies for sonographic biometric examination. EFWs were calculated according to two formulas and compared with the corresponding birth weight (BW). We also assessed the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of EFW for the diagnosis of small-for-gestational age (SGA) and large-for-gestational age (LGA) neonates.

RESULTS

A total of 374 subjects who delivered within 7 days after the sonographic examinations was recruited. Using the Hadlock formula, the median absolute difference between EFW and BW was 182 g (15-308 g) and the median percentage difference was 5.3% (0.5-9.1%), whereas it was 230 g (62-367) and 7.1% (2.1-10.4%) for the Woo formula (p < 0.001). Several factors, namely the fetal presentation, gender, and high amniotic quantity, showed no evident impact on this predictive difference. Among the 175 women who delivered within 2 days after ultrasound, the sensitivity and specificity of Hadlock EFW were 100% and 97.1% for the detection of SGA and 48.1% and 97.3% for the detection of LGA, respectively. The PPV and NPV were 44.4% and 100.0% for the detection of SGA and 76.5% and 91.1% for the detection of LGA, respectively.

CONCLUSIONS

EFWs calculated using the Hadlock formula for our research subjects were as accurate as those reported for other populations. The predictive performance showed a high NPV for the diagnosis of SGA and a relatively acceptable PPV for the diagnosis of LGA. © 2017 Wiley Periodicals, Inc. J Clin Ultrasound 45:465-471, 2017.