Not all MC twin pregnancies in which there is a difference in size of the twins and different levels of amniotic fluid, is Twin to Twin Transfusion Syndrome (TTTS) the cause. These findings are also seen in unequal placental sharing. In this case the twins do not have an equal access to the placenta. This leads to the smaller one having slower growth and lower amounts of amniotic fluid. This usually gets progressively worse and can lead to stillbirth of the smaller twin. As in one of the sections above, death of one of the twins will also place the survivor at risk because of the blood vessel connections in the placenta. In unequal placental sharing the larger normally growing twin does not have increased amniotic fluid in contrast to TTTS. Unequal sharing and TTTS can co-exist to varying degrees.
Ultrasound evaluations provide us with the information to determine the severity of the situation. The greater the degree of size/weight difference between the twin fetuses the more serious the problem is. Also the less fluid present in the sac of the smaller twin, the more serious the situation. We also monitor the blood flow in the umbilical cords of the fetuses using Doppler ultrasound. A high resistance pattern is characteristic in the smaller, sicker one, and a normal one in the larger.
There are no treatments that can be performed to improve the situation in this case. Amnioreduction and laser treatment are not appropriate, and could make things worse. Management is based on keeping a very close watch on the smaller twin. This may allow us to see when the smaller one is getting sick. Depending on the stage of the pregnancy this may lead to hospitalization for closer follow-up or delivery. It is very important to keep such a close eye on the smaller one because stillbirth will possibly lead to serious problems even in the survivor.