DIAGNOSIS, PATHOPHYSIOLOGY, AND TREATMENT OF CHRONIC TWIN-TO-TWIN TRANSFUSION SYNDROME

The discovery of a 'stuck twin' during an ultrasound examination has o ften been equated with twin-to-twin transfusion based to a great exten t on postnatal confirmation of discordant fetal size and hemoglobin co ncentration. However, the diagnosis of twin-to-twin transfusion cannot be made with certainty after birth since virtually all monochorionic gestations have placental anastomoses and there are many causes of gro wth deficiency and abnormal hemoglobin concentration. The purpose of t his study is to investigate the pathophysiology of chronic twin-to-twi n transfusion syndrome and apply the findings to the development of a management algorithm. In 42 twin gestations with stuck twin associated with acute hydramnios, we performed targeted ultrasound cordocentesis in each fetus and therapeutic amniocentesis. The diagnosis of chronic twin-to-twin transfusion syndrome required: sonographic evidence of m onochorionicity; rapid reaccumulation of fluid after amniocentesis; di scordant fetal size, and divergent fetal hematocrit measurements with at least one above or below the 95% confidence interval for gestationa l age. These criteria were met in 20 of 42 (48%) pregnancies. The mean gestation was 23.8 +/- 2 weeks (range 21-27 weeks). In 4 pregnancies, the transfer of adult RBCs from the donor to the recipient was docume nted. Monochorionicity was confirmed in all postnatally. All recipient s had polycythemia and hyperproteinemia. Hydrops developed only in the recipient twin (6 of 20) and was associated with an elevated umbilica l venous pressure. All pregnancies were treated with aggressive serial therapeutic amniocenteses. There was no objective evidence that amnio centesis altered the magnitude of the shunt. In addition, 1 patient ch ose pregnancy termination, 3 a selective fetocide of the donor twin, a nd 4 transfusion therapy. The mean gestation at delivery was 29 +/- 4 weeks and the perinatal mortality rate 58% (23 of 40 fetuses). Surviva l was significantly lower when symptoms appeared <25 weeks (10 of 30 v s. 7 of 10, p = 0.04). The presumptive diagnosis of twin-to-twin trans fusion is frequently erroneous and an accurate diagnosis required ante natal evaluation. Hydrops results from heart failure secondary to a co mbination of polycythemia and hyperproteinemia Because no antenatal th erapy is clearly effective and the likelihood of neonatal survival is greater when symptoms first appear greater than or equal to 24 weeks, an invasive evaluation should be limited to those pregnancies which ei ther transfusion present <25 or greater than or equal to 25 weeks with a hydropic fetus.