Antenatal Ultrasound Measurement of Fetal Abdominal Subcutaneous Tissue Thickness as a Predictor of Fetal Birth Weight

Abstract Objectives To correlate fetal abdominal subcutaneous tissue thickness (FASTT) measured by transabdominal ultrasound and birth weight measured immediately after delivery and to obtain cut-off values for FASTT to predict small and large for gestational age babies in the Egyptian population. Background Fetal weight estimation is a crucial part of antenatal and intrapartum care as it forms the basis for decision making in obstetric care. Various studies compared the accuracy of different ultrasound fetal weight estimation formulas to determine the most accurate one, but current evidence still indicates significant error levels. FASTT measurement can be used to improve ultrasonographic fetal weight assessment reducing potential perinatal complications associated with small and large for gestational age fetuses. Patients and Methods A prospective cohort study conducted in Ain Shams University Hospitals on 86 pregnant women with normal singleton pregnancies between 24 and 40 weeks of gestation. FASTT was measured in millimeters at the anterior third of the abdominal circumference and birth weight was recorded immediately after delivery. Results This study concluded that FASTT showed high statistically significant correlation with EFW by Hadlock formula IV (1985) (r = 0.624, p- value = <0.001) and BW (r = 0.749, p- value = <0.001). FASTT showed higher sensitivity (84.09%) than specificity (64.29%) as a predictor of both SGA and LGA, but it showed higher sensitivity and specificity in LGA (sensitivity 100%, specificity 97.5%) compared to SGA (sensitivity 81.1%, specificity 73.5%). The best cut-off value of FASTT for LGA was 7.1 mm and that of SGA was 4.9 mm. No statistically significant correlation was found between FASTT and any of the maternal age, fetal gender or mode of delivery. Conclusion FASTT can be used as a predictor for birth weight; it is a better indicator of LGA than SGA. FASTT can be incorporated into fetal weight estimation formulas as a method to increase their accuracy especially at birth weight extremes. A study on a larger scale of Egyptian population should be conducted to generate fetal weight estimation formulas based on the Egyptian ethnicity to be the reference for medical practice in Egypt.