Prediction of fetal weights in twins

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

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.

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%.

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.