There are certain events in life that we have never heard of and cannot imagine what they are about until we go through them ourselves. This is the case with twin-to-twin transfusion, a complication that occurs in twin or multiple pregnancies and causes great concern for parents when they encounter it.
Twin-to-twin transfusion syndrome, as it is called by doctors, is a complication caused by the sharing of the same placenta by two babies during pregnancy, but who are separated in different amniotic sacs. This situation is also known as diamniotic and monochorionic pregnancy, which refers to when there is a single placenta to nourish and sustain both babies. The big problem is caused by an imbalance in the blood flow, which should be divided and provide blood to both babies but is not always able to do so “properly,” which can result in babies with very disproportionate sizes.
The flow of blood passes through placental vein and artery connections that are linked to both babies, and this imbalance will make one baby the donor of blood and the other the recipient, who will be the larger and better developed baby.
How is it Diagnosed and is There Treatment?
Through ultrasound examination it is possible to analyze the amount of amniotic fluid in both sacs, and in these cases it is found that one sac has increased fluid and the other reduced. This condition is called polyhydramnios when there is more fluid than expected, and oligohydramnios when the volume is reduced. The sac with above normal levels is where the larger baby, also called the recipient, is found. In the sac with less fluid is the smaller and less developed baby, also called the donor.
Another feature observed during the ultrasound exam is the urinary bladder of the babies. The larger baby has a bigger bladder filled with fluid, while the smaller baby’s bladder is almost imperceptible due to the lack of fluid inside. The method of assessing the amount of amniotic fluid is different from that used in a single pregnancy, as the amount of fluid in the vertical pocket is observed. When the amount of fluid in the pocket is 8 cm or more, polyhydramnios is diagnosed, and when less than 2 cm, oligohydramnios is diagnosed.
As for treatment, two methods are used to try to reverse the situation: serial amniodrainage, where excess amniotic fluid is removed from the recipient baby’s sac. The goal is to reduce the chances of premature birth and it may be performed as many times as needed to decrease the excess fluid. However, it does pose some risks to the fetus, with a 15% risk of cerebral palsy and a 66% success rate in results.
There is also fetoscopy, which involves cauterizing the vessels and arteries connecting the fetuses. The focus here is to interrupt blood exchange between the twins. It has an 85% chance of success, with a 4% risk of cerebral palsy in the babies. When twin-to-twin transfusion is diagnosed, it is necessary to perform one of these techniques; otherwise, there is reported to be a 100% risk of fetal death. For further information and appropriate treatment, a specialist in Fetal Medicine should be consulted and a full evaluation done.
See also: Twin Pregnancy – What Changes to Expect in the Mother’s Body?
Photo: Jill M
