Interpretation
It is apparent that placental communication vessels crossing between the twins may affect hemodynamics of both cardiovascular systems in wide variations. However, to date the pathophysiology of TTTS is still not fully understood and a commonly accepted therapy to treat severe cases of TTTS does not exist. Moreover, there are important unanswered questions related to the AR protocol. How much of the amniotic fluid volume should be removed? What should be the rate of fluid drainage? What are the criteria for amniotic fluid drainage termination? Is the procedure restricted to specific timing during gestation? The research efforts to answer these open questions are still going on.
It has been reported that management of TTTS either with FLA or AR prolongs the pregnancy without guarantee for normal growth of both infants 8, 11. The present results demonstrated that the controlled AR is safe and can be repeated if needed independent of the gestation week. Therefore, we believe that controlled AR with slow flow rate under gravity is less invasive then FLA. In contrast to suggestions that the fluid should be drained as quickly as possible28, we have shown that gravity driven fluid drainage at slow rates is more favorable for the fetuses, due to both a gradual pressure drop and increase in the umbilical flow rate from mother to fetus. Furthermore, it seems that gradual reduction of the amniotic volume, as well as decreasing the amniotic pressure on the placental chorionic vessels result in more moderate impact on the cardiovascular system for both fetuses. Nevertheless, the controlled AR procedure resulted in a higher survival rate and positive long-term outcomes compared to other studies10, 11, 13, 26-28.