Detection of the growth-restricted fetus: which centile charts?

Abstract

Introduction: Poor identification of fetal growth restriction (FGR) continues to impede reductions in the rate of stillbirth. Better detection of FGR will likely be afforded by the use of late pregnancy ultrasound. However, which estimated fetal weight (EFW) centile charts should be used is not clear. Methods: This is a retrospective cohort study of women undergoing third trimester ultrasound for clinically suspected FGR. Four models of EFW centile calculation were compared: Australian birthweight (BW) centiles, ultrasound-derived EFW centiles and customised EFW centiles with and without maternal ethnicity. The models were assessed by a comparison with actual BW centile and their sensitivity, specificity, positive predictive value and negative predictive value in determining FGR (BW <10th centile). Results: Of the 107 women who met inclusion criteria, 78 (73%) had a BW <10th centile [median (IQR) BW centile: 4th (2nd–11th)]. Non-customised ultrasound-derived EFW centiles were the most accurate and customised centiles the least. The mean error, sensitivity, specificity, positive predictive value and negative predictive value for each were as follows: 0.4, 0.77, 0.45, 0.79 and 0.42 and −4, 0.88, 0.28, 0.77 and 0.44, respectively. Discussion: Non-customised ultrasound-derived EFW centiles appear the most useful in the determination of fetal weight centiles.