High Risk Pregnancies

 

10 things to know about Twin-to-Twin Transfusion Syndrome (TTTS)

  1. In the United States, monozygotic twins (identical twins) occur in 3-5/1000 pregnancies. The identical twins can be monochorionic (sharing a single placenta) or dichorionic (having different placentas). Approximately 75% of identical twins are monochorionic.
  2. Only monochorionic twins (sharing a single placenta), where the blood from one twin circulates to the other twin, are at risk for Twin-to-Twin Transfusion Syndrome (TTTS). TTTS occurs in 5-40% of monochorionic twins.
  3. TTTS is a disease of the shared placenta where abnormal blood vessels connect the umbilical cord and circulations of the twins. One twin always 'donates' blood to the other.
  4. Twin-to-twin transfusion syndrome (TTTS) is a specific complication of monochorionic, monozygotic twins and may happen in higher order pregnancies (triplet, quadruplets, etc) if there are identical twins present. It is a result of an intrauterine blood transfusion from one twin to another twin. The donor twin is often smaller with intrauterine growth restriction and anemic, may be "stuck" in the amniotic membranes in "stuck twin syndrome," and is at highest risk of dying in utero. The recipient twin is usually larger and can have excess blood volume and fluid. Either twin can become swollen (edematous) and have heart failure or " hydrop."
  5. Severe TTTS develops early at 16-18 weeks' gestation. Polyhydramnios (excess) develops in the sac of the recipient twin because of excess blood, volume overload, and increased fetal urine output while oligohydramnios (low fluid) develops in the sac of the donor twin. TTTS is also referred to as "poly-oli syndrome." Both twins are at risk of dying in utero.
  6. Moderate TTTS develops at 24-30 weeks' gestation. Polyhydramnios and oligohydramnios usually do not develop. The donor twin becomes anemic, lags in growth and can develop heart failure. The recipient twin becomes larger and can develop hypertension, enlarged heart, fluid overload, and jaundiced at birth.
  7. Mild TTTS develops in the third trimester. Polyhydramnios and oligohydramnios usually do not develop. Twin size can differ by more than 20%. TTTS can happen at birth during the time between clamping of the umbilical cords, where the second twin may receive a significant blood transfusion from the placenta.
  8. Severe TTTS has 60-100% mortality rate. Mild-moderate TTTS is associated with premature delivery. Death of one twin is associated with neurological defects in 25% of surviving twins.
  9. Pregnant women with twins may notice rapidly growing abdomen, preterm labor, and ruptured membrane.
  10. Observation and bed rest is best with early delivery may be the best option for mild cases. Laser fetal surgery to block the abnormal blood vessel communication can be considered to separate the two blood circulation in moderate to severe cases.

Resources:

http://multiples.about.com/gi/dynamic/offsite.htm?zi=1/XJ&sdn=
multiples&zu=http%3A%2F%2Fbms.brown.edu%2Fpedisurg%2FFetalTreatment.html
http://www.emedicine.com/med/topic3410.htm

        
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