Premium
Incorporation of femur length leads to underestimation of fetal weight in asymmetric preterm growth restriction
Author(s) -
Proctor L. K.,
Rushworth V.,
Shah P. S.,
Keunen J.,
Windrim R.,
Ryan G.,
Kingdom J.
Publication year - 2010
Publication title -
ultrasound in obstetrics and gynecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.202
H-Index - 141
eISSN - 1469-0705
pISSN - 0960-7692
DOI - 10.1002/uog.7605
Subject(s) - medicine , biparietal diameter , fetus , fetal weight , umbilical artery , birth weight , obstetrics , fetal growth , head circumference , pregnancy , genetics , biology
Objective To review the performance of a variety of biometry formulae for estimated fetal weight (EFW) in the management of severely growth restricted fetuses with abnormal umbilical artery Doppler at a single perinatal institution. Methods Forty‐three pregnancies were retrospectively reviewed. Inclusion criteria were: chromosomally/ structurally normal fetus; complete ultrasound biometry at ≤ 7 days from delivery; EFW < 10 th centile; absent/reversed end‐diastolic flow in the umbilical arteries; and delivery at < 32 + 6 weeks. EFW accuracy and precision were compared among nine formulae utilizing combinations of head circumference (HC), biparietal diameter (BPD), abdominal circumference (AC) and femur length (FL) measurements. Results Twenty‐six (60.5%) fetuses showed asymmetric growth (HC/AC ratio > 95 th centile). Analysis of the systematic and random errors associated with each formula showed that the birth weight of asymmetrically‐grown fetuses was most closely approximated by the Hadlock equation that utilized BPD and AC measurements only. The birth weight of symmetrically‐grown fetuses was most closely approximated by EFW derived from Hadlock equations that utilized ≥ three biometry measurements, including FL. Incorporation of FL into Hadlock formulae led to significant underestimation of birth weight in the fetuses with asymmetric growth (mean percentage error ± SD: EFW FL–AC , −13.3 ± 9.8%; EFW BPD–FL–AC , −10.8 ± 9.8%; EFW HC–FL–AC , −11.8 ± 9.3%; EFW BPD–HC–FL–AC , −11.7 ± 9.5%; P < 0.001). The same equations were accurate in fetuses with symmetric growth (EFW FL–AC , 3.1 ± 10.0%; EFW BPD–FL–AC , 1.0 ± 8.9%; EFW HC–FL–AC , 0.3 ± 8.7%; EFW BPD–HC–FL–AC , 0.4 ± 15.5%). Use of the best performing equation (Hadlock 3), which does not include FL, to estimate weight in asymmetrically‐grown fetuses over 28 weeks' gestation, would have reduced the proportion of those with an underestimation of fetal weight of > 100 g from nine (50.0%) to three (16.7%). Conclusions Biometry methods that exclude FL should be considered in asymmetric intrauterine growth restriction associated with abnormal umbilical artery Doppler waveforms. Copyright © 2010 ISUOG. Published by John Wiley & Sons, Ltd.