Maternal and fetal digoxin levels in cases of twin-twin transfusion syndrome (TTTS)

Background: Even though invasive intrauterine techniques for the treatment of TTTS such as punction of amniotic fluid and laser coagulation of placent al vascular anastomoses are established methods in specialized centers, inv asive methods are not always sufficiently successful. In conservative treat ment of TTTS oral or intravenous maternal digoxin therapy in order to impro ve fetal cardiac insufficiency in combination with or after failure of inva sive techniques is an useful method. Patients and Methods: We investigated 12 TTTS pregnancies and 4 singleton p regnancies, which had been treated by maternal digoxin treatment for TTTS o r arrhythmias, respectively. At birth, which was performed by means of caes arian section, venous cord blood samples of the newborns and venous materna l blood samples were collected, centrifugated and stored at minus 20 degree s C. Digoxin determinations were performed by radioimmunoassay. Results: Fetal digoxin levels varied between 0.38 and 1.73 ng/mi, maternal levels ranged from 0.97 to 3.23 ng/ml. The fetomaternal digoxin gradient re ached a mean of 0.56 (range 0.35 to 1.09). Donator and acceptor gradients w ere comparable and increased with birth weight or gestational week, respect ively. Conclusions: In cases of pregnancies with TTTS a relatively high maternal d igoxin level is necessary, especially during early gestational weeks, in or der to reach therapeutical levels in the fetal circulation, Too low dosages might be responsible for unfavourable results in digoxin treatment of TTTS . Whether the maturation of placental villi during gestation could be the r eason for increasing digoxin gradients requires further investigations.