Fetal transfusion refers to the transfer of blood into an unborn baby. A rare condition called twin-to-twin transfusion syndrome (TTTS) is also known as fetal transfusion syndrome. TTTS only occurs during the gestation of identical twins. The placental blood supply is shared, often leaving one of the twins much weaker than the other. Fetal transfusion may also describe an intrauterine blood transfusion performed to treat an anemic fetus before birth.
A fetal blood transfusion is given to keep a baby healthy until delivery. If a fetus is rhesus (Rh) positive and the mother is Rh negative, antibodies may form that destroy the red blood cells of the unborn baby, causing anemia. Transfusion of red blood cells may be necessary to keep the fetus alive. Fetal transfusions are infused through the umbilical veins to promote the absorption of blood cells. The fetal transfusion may be repeated every one to four weeks until delivery.
Fetal transfusion syndrome results when the blood vessels connect in the placenta of an identical twin pregnancy, causing the unborn twins to share blood. The twin that shares the blood is called the donor twin, and the twin that receives the extra blood is called the recipient twin. Many times, one or both of the babies die before birth or suffer with disabilities once born.
Physical effects of the shared blood supply on the unborn twins are serious. The donor twin often has a lower blood volume and is anemic from the decreased blood supply. Recipient twins commonly have a high blood volume and blood pressure, resulting in cardiac distress. The urine output of the babies may increase or decrease, causing alterations in the amount of amniotic fluid surrounding each baby.
Treatment of fetal transfusion syndrome may involve the aspiration of the extra amniotic fluid from the recipient twin’s amniotic sac or removing the membrane between the twins’ amniotic sacs so the amniotic fluid can be shared. Another treatment method is to interrupt the passage of blood between the babies. Part of the umbilical cord may need to be surgically blocked, or the responsible placental veins may be cauterized with a laser.
Fetoscopic laser ablation is one of the procedures used to restrict the sharing of the donor twin’s blood supply. An ultrasound fetoscopy is used to locate the blood vessels involved, then the endoscopic laser destroys the blood vessels. This procedure often ensures the survival of both babies.