Diagnostic accuracy of different ultrasonographic growth parameters in predicting discordancy in twin gestation: a different approach.

The purpose of this study was to examine the predictability of intrapair percentage differences of ultrasonic fetal biometric parameters in detecting twin discordancy. Fetal biometric parameters obtained in 90 twin gestations within 7 days of delivery were analyzed. Intrapair differences of 5% and 10% were used for biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), femur length, and HC/AC to assess their predictive value. Statistical analysis was performed using chi 2 test and Fisher's exact test. Receiver operator characteristic (ROC) analysis was done to determine if there was a difference between absolute and intrapair differences. Intrapair AC and HC differences of 5% were found to have significantly higher true positive rates in detecting discordancy. At an intrapair difference of 10%, AC and BPD were found to have high sensitivity rates in detecting discordancy. ROC analysis did not show any difference between use of absolute and intrapair difference in predicting discordancy (P = 0.0001). We conclude that fetal AC is the most significant sonographic parameter in detecting discordancy in twins.