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MS WordPerinatologist Corner - C.E.U/C.M.E. Modules
Twins: Antepartum assessment and Intrapartum management
Sponsored by The Indian Health Service Clinical Support Center
9 Twin Pregnancy: Double Trouble?
Step 9. Twin to twin transfusion syndrome
The most difficult problem in monochorionic pregnancy is twin to twin transfusion syndrome.
(Fox) This complication is usually suggested in the second trimester on the basis of sudden onset rapid fundal growth. On ultrasound, polyhydramnios (deepest pocket of amniotic fluid greater than 8 cm) in the recipient twin, and oligohydramnios (deepest pocket <2 cm) in the recipient or “stuck” twin is diagnostic. This may be quite striking. There may also be a size differential between the two twins. The classic teaching about anemia in the donor and polycythemia in the recipient is probably a rare occurrence. This is an isovolumetric transfer between the twins that occurs when a placental artery of the donor anastomoses directly to a placental vein in the recipient, which situation is not reciprocated in the recipient.
The recipient experiences heart failure from volume overload (systolic dysfunction). The donor initially may experience shock, but, if it survives, will compensate with severely elevated peripheral resistance (increased afterload), and eventually will develop diastolic cardiac dysfunction. In an attempt to preserve cerebral perfusion, it will shunt as much blood as it has to its head, not perfuse its kidneys, and develop severe oliguria/oligohydramnios, such that it may appear to be “shrink-wrapped” or “stuck” in its amniotic sac.
Management of this situation is difficult.
The standard of care until quite recently was serial amniocenteses with amnioreduction to keep the sac of the recipient twin decompressed. Needle septostomy to try to equalize the volume of amniotic fluid in the two sacs has also been done. The survival of at least one twin with these procedures is between 65-75%, but survivors have a significant risk of neurological disability, and are almost all delivered very prematurely. Most recently, laser coagulation of the intra-placental anastomoses has been shown to result in a better survival rate of at least one, and possibly both, twins, as well as a lower risk of CNS damage in survivors.
At present, in the United States, this procedure can only be done at a few specialized centers with expertise in fetoscopy, and may be accompanied by a significant risk of preterm labor and preterm premature rupture of membranes. This is obviously a situation which requires expeditious referral.
