Ultrasonic Estimation of Fetal Weight: Are Averaged Triplicate Measurements More Accurate Than Single Measurements?

Objective

To assess whether, and to what extent, performing triplicate measurements can improve accuracy of estimation of fetal weight (EFW) compared to single measurements.

Methods

This was a prospective study conducted at a single medical center. A total of 100 term parturients with an anticipated delivery within 72 hours were recruited for EFW measurements. All examinations were done with adherence to the International Society of Ultrasound in Obstetrics and Gynecology (ISUOG) guidelines. EFW was calculated using the Hadlock formula. Triplicate measurements from three different images were obtained for each parameter and the averaged values were used for clinical purposes. EFW calculated using average measurements was compared to EFW calculated using the first measurements.

Results

There was a small but significant improvement in EFW when using averaged measurements compared to single measurements (mean improvement 34 ± 105 g, P = .002). Deviance from birthweight in single measurements was significantly higher compared to averaged measurements (median deviance 198 versus 148 g, respectively, P = .005). This difference was more pronounced when assessing the 75th centile (348 versus 282 g, respectively).

Conclusions

Using triplicate measurements instead of single measurements when performing EFW confers a small, but statistically significant, improvement to EFW accuracy. Using triplicate measurements for assessing EFW should be thus considered, especially in cases suspected of growth disorders.