Estimation of fetal weight by measurement of fetal thigh soft-tissue thickness in the late third trimester.
OBJECTIVE
The accuracy of current formulae for the sonographic estimation of fetal weight (EFW) is compromised by significant intra- and interobserver variability of biometrical measurements, particularly circumferences. The aim of this study was to assess the reliability of the linear measurement of mid-thigh soft-tissue thickness (STT) and to derive a novel formula for EFW.


METHODS
This was a prospective study involving 388 singleton uncomplicated pregnancies. There were three consecutive phases: (1) to verify the relationship between STT and birth weight, (2) to derive a novel formula for EFW using femur length and STT only, and (3) to test the accuracy of the new equation. Only the 290 patients who delivered within 48 h of measurement were considered for the analysis. A comparison with other formulae was performed.


RESULTS
STT was significantly correlated with both abdominal circumference and birth weight (r(2) = 0.36 and 0.46, respectively; P < 0.001). Both intra- and interobserver variability were satisfactory (0.44 +/- 0.27 and 0.57 +/- 0.35 mm, respectively). The equation for EFW was developed using multiple stepwise regression analysis (EFW = - 1687.47 + (54.1 x femur length) + (76.68 x STT)) and tested prospectively on 69 patients. The new formula yielded results (r = 0.79) that were slightly better in accuracy than two other published equations, and had an absolute mean error of < 15% in 97% of cases.


CONCLUSIONS
Our findings confirm the potential of the linear measurement of mid-thigh STT as a valuable parameter for the sonographic assessment of fetal growth and EFW. Our new equation is apparently at least as reliable as the most widely used formulae for EFW.
Scioscia
M
M
Department of Gynaecology, Obstetrics and Neonatology, University of Medical Science of Bari, Italy. marcoscioscia@gmail.com
Scioscia
F
F
Vimercati
A
A
Caradonna
F
F
Nardelli
C
C
Pinto
L R
LR
Selvaggi
L E
LE
D000005:Abdomen / Q000000981:diagnostic imaging / Q000196:embryology; D000328:Adult; D000465:Algorithms; D001724:Birth Weight; D003430:Cross-Sectional Studies; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000196:embryology; D005320:Fetal Macrosomia / Q000000981:diagnostic imaging; D020567:Fetal Weight; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D015588:Observer Variation; D011237:Predictive Value of Tests; D011247:Pregnancy; D011263:Pregnancy Trimester, Third; D011446:Prospective Studies; D012044:Regression Analysis; D015203:Reproducibility of Results; D013848:Thigh / Q000000981:diagnostic imaging* / Q000196:embryology; D016216:Ultrasonography, Prenatal / Q000379:methods*