This is a protocol for a Cochrane Review (Diagnostic test accuracy). The objectives are as follows:

Our primary objective is to determine the diagnostic accuracy (sensitivity and specificity) of different estimated biometric ultrasound measures using 30% thresholds with the actual birth weight discordance (BWD) as the reference standard (e.g. abdominal circumference (AC) compared with actual BWD) and to provide readers with a summary of the diagnostic accuracy of ultrasound measures for the diagnosis of BWD in twin gestations.