Discordant twins--a prospective study of the diagnostic value of real-time ultrasonography combined with umbilical artery velocimetry.
This study was undertaken to evaluate the role of Doppler velocimetry combined with intertwin differences in ultrasonographically derived estimated fetal weight, biparietal diameter, abdominal circumference, and femur length as a comprehensive test for the prediction of discordancy. The following cutoff values were used to indicate abnormal test results: delta biparietal diameter greater than 6 mm, delta abdominal circumference greater than 20 mm, delta femur length greater than 5 mm, delta estimated fetal weight greater than 15%, and delta systolic/diastolic ratio greater than 15%. Discordancy was identified when the birth weight difference exceeded 15%. The study population consisted of 58 consecutively evaluated third-trimester twin gestations. Eighteen sets of twins were discordant. None of these tests was uniformally successful in identifying twin discordancy; in three instances, all test results were normal. The diagnostic accuracy provided by ultrasonography was not significantly different from that provided by Doppler velocimetry. Overall the best predictor appeared to be the presence of either delta systolic/diastolic ratio greater than 15% or delta estimated fetal weights greater than 15%, which correctly identified 14 of the 18 discordant twins and misclassified only five of the 40 concordant pairs. This combination also had the highest positive and negative predictive values (73% and 90%, respectively).
Divon
M Y
MY
Department of Obstetrics and Gynecology, Albert Einstein College of Medicine, Yeshiva University, Bronx, NY.
Girz
B A
BA
Sklar
A
A
Guidetti
D A
DA
Langer
O
O
D001724:Birth Weight; D004200:Diseases in Twins; D005314:Embryonic and Fetal Development; D005260:Female; D006801:Humans; D011237:Predictive Value of Tests; D011247:Pregnancy; D011263:Pregnancy Trimester, Third; D011296:Prenatal Diagnosis; D011446:Prospective Studies; D014463:Ultrasonography; D014469:Umbilical Arteries / Q000502:physiology*