Occurs in identical twins sharing a placenta
By Mary Kugler, RN; as seen at About.com
Twin-to-twin transfusion syndrome occurs specifically in identical twins sharing the same placenta. It is estimated to occur in 5-10% of identical twin pregnancies. In twin-to-twin transfusion syndrome, the twins share not only the same placenta but some of the same circulation. This allows the transfusion of blood from one twin (the donor) to the other (the recipient). The donor twin becomes small and anemic, and the recipient twin becomes large and overloaded with blood.
Because the recipient twin has more blood, he/she also urinates more and has more amniotic fluid. The donor twin has less amniotic fluid; sometimes there is so little fluid that the fetus appears on ultrasound to be stuck in place on the wall of the uterus (known as "stuck twin phenomenon").
Twin-to-twin transfusion syndrome can range from mild to severe. It can occur at any point during the pregnancy, even at birth (once one umbilical cord has been clamped after delivery, the other twin may get a rush of extra blood).
Symptoms of twin-to-twin transfusion syndrome may include:
Pregnant mother - a rapidly enlarging abdomen over 2-3 weeks, as the amniotic fluid of the recipient twin builds up; premature labor, and premature rupture of membranes (water breaks early)
- Donor twin - Small for gestational age, 10-20% smaller than recipient twin, pallor (due to anemia), poor circulation
- Recipient twin - Large for gestation age, 10-20% larger than donor twin, ruddy (red) skin and jaundice (due to extra blood). An additional complication known as hydrops fetalis may develop in either twin. In this condition, fluid accumulates in some part of the fetus, such as in the scalp, abdomen, lungs, or heart.
Twin-to-twin transfusion syndrome may be suspected if a pregnant woman carrying twins finds her abdomen enlarging rapidly. The syndrome can also be detected on ultrasound examination of the uterus. If the syndrome is mild, or not detected on ultrasound, the appearance of the twins at birth may identify the syndrome. Also, a complete blood cell count done after birth will show anemia in the donor twin and excess red blood cells in the recipient twin.
Treatment before birth:
It is possible to seal off some or all of the blood vessels the twins share using a laser. This would separate the circulation of the fetuses and end twin-to-twin transfusion. However, this requires operating while the fetuses are still in the womb, and it may cause serious complications.
There are other procedures which can be done, such as repeated drainage of excess amniotic fluid from the recipient twin by amniocentesis. A hole can be punched between the twins' two amniotic sacs to equalize the fluid between the sacs. However, neither of these procedures stops the twin-to-twin transfusion.
If one twin is dead or dying, that part of the umbilical cord can be blocked so that blood no longer goes to that twin. The pregnancy can also be voluntarily terminated.
The most conservative treatment is to simply watch and wait. The pregnancy would be followed closely with frequent ultrasound examinations, with the option of delivering the twins by cesarean section if medically necessary.
Treatment after birth:
Medical care of the twins after birth is focused on problems related to premature birth (the more premature, the more problems are likely to develop). Newborns with twin-to-twin transfusion syndrome may be critically ill at birth and require treatment in a neonatal intensive care unit. The donor twin is treated for anemia and the recipient twin for excess red blood cells and jaundice. Any complications that developed during the pregnancy, such as hydrops fetalis, are also treated.