Prediction of fetal weights in twins

Abstract

Objective: To determine the accuracy of sonographic weight estimation of twin fetuses.

Methods: In 73 twin-pregnancies, fetal weight estimation by ultrasound was performed within 7 days prior to delivery. Fetal head biparietal diameter and abdominal circumference were measured. The coefficient of correlation (r), and the ratio between estimated weight and actual weight were calculated.

Results: The coefficient of correlation was r = 0.954 between estimated weight and actual birth weight. The ratio between the two parameters was 1.025, the standard deviation 0.089. In our study, 41% of the antenatal estimated weights deviated less than 5% from the actual birth weight. For 72% of all estimated weights, the deviation was less than 10%. Ultrasonographic prediction of actual weight below the 10th percentile level showed a sensitivity of 85%, predictive value of 80% and specificity of 87%. In detecting inter-twin discordance > or = 20%, the respective values were 64%, 64% and 91%.

Conclusions: Antenatal estimation of birth weight by ultrasound correlates well with the actual weights of twin fetuses. Prediction of individual fetal weight seems to be more accurate than prediction of inter-twin discordance.