Role of fetal length in the prediction of fetal weight

Nir Melamed, Yariv Yogev, Nechama Linder, Zeev Efrat, Ron Bardin, Arnon Wiznitzer, Israel Meizner

Research output: Contribution to journalArticlepeer-review

Abstract

Objectives-The purpose of this study was to compare the accuracy of routine fetal biometric indices in the prediction of fetal length and to determine whether more accurate sonographic measures of fetal length can improve the accuracy of fetal weight estimation. Methods-The accuracy of the common sonographic fetal biometric indices for predicting fetal length was determined using 3689 sonographic weight estimations performed within 3 days before delivery. The fetal length at the time of the sonographic examination was assumed to be equal to the neonatal length, which is routinely measured within 24 hours of delivery. Two new regression models for fetal weight estimation, one with and one without fetal length as an independent variable, were generated to determine the potential contribution of more accurate predictors of fetal length to the accuracy of fetal weight estimation. Results-Abdominal circumference was a significantly more accurate predictor of fetal length (r = 0.732) compared with femur length (r = 0.712), biparietal diameter (r = 0.644), and head circumference (r = 0.661; P < .05), although each of these biometric indices explained only about 50% of the variance in fetal length (R2 = 0.423-0.548). The addition of fetal length as an independent variable to a birth weight prediction model significantly improved the model's correlation with birth weight(r = 0.917 versus 0.903; P= .006), systematic error (0.2% versus 0.6%; P< .001), random error (6.7% versus 7.5%; P < .001), mean absolute percent error, and the proportion of estimations within 5% and 10% of birth weight. Conclusions-The correlation between routine biometric indices and fetal length is limited. Identification of new fetal sonographic biometric indices with greater predictive accuracy for fetal length may improve the accuracy of fetal weight estimation.

Original languageEnglish
Pages (from-to)687-694
Number of pages8
JournalJournal of Ultrasound in Medicine
Volume31
Issue number5
DOIs
StatePublished - 1 May 2012

Keywords

  • Estimation
  • Fetal
  • Height
  • Length
  • Weight

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