Doppler flow velocity waveforms in fetal surveillance of twins: a prospective longitudinal study.

In 37 consecutive twin pregnancies, monthly Doppler sonographic measurements were made of blood flow velocity waveforms of the internal carotid and umbilical artery of each fetus. A total of 197 Doppler studies were performed. Of the 74 infants, 23 were small for gestational age (SGA). Thirty-five of the SGA Doppler studies were abnormal, giving an overall sensitivity for predicting SGA fetus of 58% and a positive predictive value of 71%. These data are not as sensitive and specific as our earlier data; however, Doppler criteria preceded sonographic diagnosis of SGA by a mean interval of 3.7 weeks and demonstrated better sensitivity and specificity. A combination of these parameters improves sensitivity to 84%. We conclude that Doppler velocimetry complements real-time ultrasonography for the early diagnosis of abnormal growth in twin pregnancies.