Pathophysiology of polyhydramnios in twin transfusion syndrome

In 3 cases of severe twin transfusion syndrome we demonstrate that the concentration of atrial natriuretic factor (ANF) in the cord blood of recipient twins is significantly elevated compared to that of donor twins. The discrepancy between recipient and donor concentration correlates with the volume of transfusion. The following pathophysiological mechanism for explaining polyhydramnios in recipient twins is proposed: chronic overload in recipient twins causes enhanced release of ANF from the fetal heart. Consequently, increased fetal urine production leads to polyhydramnios, which is additionally enhanced by inhibition of ADH release.