Objective: To evaluate the role of umbilical Doppler velocimetry combined with ultrasonographic intertwin differences derived from estimated fetal weight, biparietal diameter, abdominal circumference and femur length as a comprehensive test for the prediction of discordancy.
Methods: The sets of twins were studied with real-time ultrasonography for morphometric measurements and with duplex Doppler velocimetry for the S/D ratio of the umbilical artery in third trimester. The following cutoff values were used to indicate abnormal test results: delta biparietal diameter > 6 mm, delta abdominal circumference > 20 mm, delta femur length > 5 mm, delta estimated fetal weight > 15% and delta systolic/diastolic ratio > 15%. Discordancy was identified when the birth weight difference exceeded 15%.
Results: Among the 52 sets of twin pregnancies studied, 40 sets of twins fulfilled the study criteria. Thirteen sets of twins were discordant (32.5%) The mean gestational age at delivery was 37.15 +/- 2.24 weeks (range 28-41 weeks). The diagnostic accuracy provided by ultrasonographic morphometries was not significantly different from that provided by umbilical Doppler velocimetry. Overall the best predictors appeared to be the presence of either delta systolic/diastolic ratio > 15% or delta estimated fetal weights > 15% with sensitivity and specificity values of 92% and 70%, respectively.
Conclusion: Real-time ultrasonography combined with umbilical artery velocimetry is useful in predicting discordant twins.