Umbilical blood waveforms in fetal surveillance of twins.

Umbilical arterial velocity waveforms were recorded in 69 pairs of twins by means of continuous-wave Doppler analysis and an Angioscan spectrum analyzer. A systolic/diastolic ratio was measured for each twin. The sum of the systolic/diastolic ratio was calculated and the difference between each twin was expressed as the delta systolic/diastolic ratio. Significant differences in delta systolic/diastolic and neonatal weight were previously set at 0.4 and 350 gm, respectively. Sonography was used for fetal age confirmation and diagnosis of fetal growth retardation. All neonates were weighed; at birth gestational age was assigned by Dubowitz criteria and categorized as adequate-, small-, or large-for-gestational age. The sensitivity, specificity, and predictive value of the delta systolic/diastolic ratio were determined. The perinatal implications of this test in the management of twin pregnancy are discussed.