Accuracy of sonographic fetal weight estimation in full-term singleton pregnant women

Abstract

Objectives: To investigate the factors which might influence the sonographic fetal weight estimation (SFWE) accuracy.
 Methods: This prospective study was conducted among 949 singleton term pregnant women who delivered at a tertiary center, from January 2017 to December 2017. All participants’ maternal (i.e. parity, age, body mass index and gestational weight gain during pregnancy), fetal sonographic (i.e. fetal presentation, amniotic fluid index, localization of placenta and estimated fetal weight) and neonatal (birth weight and gender) characteristics were recorded. A p<0.05 was considered significant.
 Results: The mean absolute percent error (APE) values of SFWE was 8.2±6.5 percent, and overall failure ratio (APE >10%) was 33%. In failure group, primiparous woman and cephalic presentation fetus were significantly more common compared to accuracy group (55.9% vs.44.8%; p=0.001 and 98% vs. 95.2%; p=0.03, respectively). In contrast, the mean neonatal birth weight (NBW) value was significantly lower in failure group compared to success group (3250±565 gr vs. 3404±410 gr; p=0.001). The correlation between SFWE and NBW was linear, however negative, and significant (p=0.001). Logistic regression analysis revealed that primiparous woman, cephalic presentation fetus and <3300 gr NBW were independent risk factors for the SFWE failure (relative risks were 1.6, 2.8 and 2.4 respectively, p<0.05).
 Conclusion: SFWE has a high correlation with NBW, however it’s accuracy is still unsatisfactory, and depend on many unpredictable and inconsistent factors.
 How to cite this:Tas EE, Kir EA, Yilmaz G, Yavuz AF. Accuracy of sonographic fetal weight estimation in full-term singleton pregnant women. Pak J Med Sci. 2019;35(1):34-38. doi: https://doi.org/10.12669/pjms.35.1.373
 This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Evaluating the accuracy of sonographic fetal weight estimations using the Hadlock IV formula in a Chinese population

“…In our analysis, prepregnancy and delivery BMI, prepregnancy and delivery weight and height, GA, the use of IVF, the time interval between the ultrasound and birth, the fetal presentation, the BPD, the HC, the AC, the FL, and the amniotic volume were not found to be statistically related with SFWE, which is in line with the findings of several reports ( 5 , 10 - 13 ) but contradicts those of other studies ( 14 , 15 ).…”

“…The Hadlock formula is one of the oldest and most popular formulas in China. Research has shown that a number of maternal or fetal factors may affect the accuracy of sonographicbased fetal weight estimation (SFWE) ( 5 ), which is used to predict FW. An SFWE that falls within 10.0% of the neonatal birth weight is considered accurate.…”

Is accuracy of estimated fetal weight improved by better image quality scores?

“…The accuracy of the EFW was assessed by determining the absolute value of the difference between the PBW and the actual birth weight, divided by the latter; this difference defined the “EFW error” and was expressed as a percentage for each examination in line with other publications assessing EFW accuracy 12,14,18,21 . EFW errors greater than 10% were identified and defined as inaccurate EFW.…”

“…To limit the biases associated with the variation of the intervals between the ultrasound scan and birth (or Δ, expressed as days between the delivery and the ultrasound), the projected birth weight (PBW) was determined by adding to the EFW assessed on the day of the ultrasound 30 g per day until the birth 19,20 The accuracy of the EFW was assessed by determining the absolute value of the difference between the PBW and the actual birth weight, divided by the latter; this difference defined the "EFW error" and was expressed as a percentage for each examination in line with other publications assessing EFW accuracy. 12,14,18,21 EFW errors greater than 10% were identified and defined as inaccurate EFW. Because of the inclusion of both novice operators and extreme fetal weights in the sample (no non-inclusion criteria related to fetal growth restriction or macrosomia), an additional category of seriously inaccurate EFW errors (≥15%) was also defined and reported.…”

“…Methods to improve comparisons between actual birth weight and EFW when the scans are performed 4 days or more before birth include adding 25–30 g per day during the third trimester 19,20 . Many of these publications seek to compare the accuracy and potential clinical utility of different EFW formulae 10,14 and often characterize measurement inaccuracy by identifying EFW with a mean error greater than a threshold of 10% or 15% of birth weight 13,18,20,21 . The results of recent studies using this method have established that the reliability of the three‐indicator formula of Hadlock et al in 1985 10,22 exceeds that of the other formulae tested in the general population (mean error 7.5%).…”