Sonographic Fetal Scalp Thickness as a Potential Indicator of Estimated Fetal Weight, in the Third Trimester of Pregnancy

The aim of this study was to investigate the usefulness of recording sonographic fetal scalp thickness (FST) to predict the estimated fetal weight (EFW), in third trimester of pregnancy. A cohort of 175 uncomplicated singleton pregnancies, at 27 to 40 gestational weeks, was included in this study. The FST was measured with sonography and defined as the distance between the fetal skin and the outer table, on a cross-section of the skull, along the parietal aspect of the fetal head. Measurements were taken twice, and the average of the measurements was recorded. The estimated fetal weight (EFW) was derived from the Hadlock’s formula. Simple linear and multiple linear regression models were performed to predict the EFW, based on the FST measures. A strong positive correlation was demonstrated between FST and the EFW (r = 0.65, P < .01). The regression equation, EFW = 4.6*FST + 2.27 was derived, with a unit increase in FST yielding a 4.6 unit rise in EFW. Fetal scalp thickness and the fetal femur length (FL) accounted for about 93% (R2 = 0.93) variability in EFW, while the fetal head circumference (HC) and FST accounted for 83% (R2 = 0.83) variance in the EFW. A potential may exist to use FST as a viable indicator of EFW and could be used in conjunction with current fetal biometric parameters to improve EFW prediction.