THE ROLE OF DOPPLER ULTRASOUND IN THE PREDICTION OF THERAPEUTIC SUCCESS IN TWIN-TWIN TRANSFUSION SYNDROME

Objective: To determine if therapeutic amniocentesis in twin-twin tran sfusion syndrome alters Doppler velocimetry, and if so, whether the al teration may be a marker of treatment success. Methods: Six consecutiv e cases of twin-twin transfusion syndrome, diagnosed at 20 to 22 weeks of gestation, were examined prospectively. Umbilical artery Doppler v elocimetry for each twin was performed at diagnosis and then weekly un til delivery. Repeated therapeutic amniocenteses were performed as ind icated to achieve normalization of amniotic fluid volume in each sac. Results: Fetal survival rate was 83% (10 of 12 infants). The initial n ow velocity waveform studies showed discordance between five twin pair s, with a difference in the systolic/diastolic (S/D) ratio of more tha n 0.4. In the sixth case, both fetuses displayed absent diastolic flow , and despite amniocentesis, the amniotic fluid volume was not adequat ely normalized and both died in utero. Diastolic flow was absent in on e fetus when first assessed in four of the six twin pairs. In four cas es, as normalization of amniotic fluid volumes occurred, the S/D ratio progressively decreased to the normal range. Before delivery, the S/D ratio difference was less than 0.4 in this group. Doppler velocimetry was not predictive of donor or recipient status. As gestation progres sed, there was a trend to accelerated growth in the smaller twin. Conc lusions: In second trimester acute severe twin-twin transfusion syndro me, there is discordance in umbilical artery Doppler velocimetry. Succ essful therapy by amniocentesis in this subset of the twin-twin transf usion syndrome, as indicated by normalization of amniotic fluid volume s, is associated with the development of concordance in Doppler veloci metry. This effect may be of use as a marker to predict outcome succes s in therapeutic interventions in twin-twin transfusion syndrome.