[Doppler ultrasonography differential diagnosis in twin pregnancies]

The prognostic value of Doppler sonography concerning the estimation of fetal weight and risk in case of fetal growth discrepancy was examined on the basis of 41 twin pregnancies. Between the 25th and 40th week of gestation we did 132 pulsed Doppler measurements of the thoracic aorta and umbilical artery of both fetuses. The prenatal Doppler values--the pulsatility index in aorta and umbilical artery respectively the maximal aortic flow velocity--were set against postnatal clinical data and morphological findings of placenta and umbilical cord. From a weight discrepancy of more than 20% a correlation between pulsatility difference in fetal aorta and particularly in umbilical artery with weight difference is evident. On the other hand conclusions only from discrepant Doppler values can't be drawn concerning divergent weight development. The difference between measured and normal Doppler values is decisive for the fetal outcome. Our standard Doppler values drawn from 27 normal twin pregnancies don't differ from those of normal single pregnancies. The worst prognostic criterion was the diastolic zero-flow in the umbilical artery. In case of a decreased but still detectable diastolic bloodflow the birth and neonatal condition were often normal, although the birth weight was low. In case of fetal transfusion syndrome these criteria can't be used to judge the fetal risk. On the one hand we found a normal pulsatility index in the umbilical artery of donor and recipient twin. On the other hand the maximal aortic flow velocity may be increased and the pulsatility index in this vessel may be decreased in donor as well as in recipient twin. This depends on the extent of fetal anemia respectively of cardial compensation.