Accuracy of Sonographic Fetal Biometry Measurements [26M]

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Ultrasound measurements are used to estimate fetal weight, a factor with significant importance in decision making. While trials have studied the validity of formulas, none have evaluated the ultrasonic measurements themselves. This study evaluated the accuracy of ultrasound measurements compared to physical measurements.


Just prior to cesarean section, patients (n=48) consented to an ultrasound. Biparetal diameter (BPD), head circumference (uHC), abdominal circumference (uAC) and femur length (FL) were measured and an estimated fetal weight (uEFW) was obtained. Within six hours of birth, the newborn's HC (tmHC) and AC (tmAC) were tape measured. The uHC, uAC, and tmHC, tmAC were entered onto an online calculator, using the Hadlock formula and compared the uUC-uAC derived EFW with the tmHC-tmAC derived EFW. Mean values were obtained and descriptive and bivariate statistics were performed.


There were no significant differences between the uAC (35.69 cm±2.67 cm) and tmAC (35.09 cm±2.04 cm) (P=.112) as well as the uHC (33.57 cm±1.48 cm) and the tmHC (35.58 cm±1.45 cm) (P=.074). However, the mean uEFW (3601 g±556 g) was significantly different from both the mean tmEFW (3545 g±380 g) and the mean actual weight (3544 g±472 g) (P<.001). However, when using only the uHC and uAC measurements alone, the EFW (3,573±528) more closely approximated the birth weight (P=.492).


It is possible to obtain accurate fetal biometry measurements at term. uEFW was more accurate in predicting birth weight when only using the uHC and uAC. Further studies will need to validate these findings and explore alternative fetal weight formulas.

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