Twin to twin transfusion syndrome is a condition in which intrauterine blood transfusion occurs from one twin to other, resulting in anemic donor twin and plethoric recipient with hemoglobin differences greater than 5 g/dL.
The donor twin is often smaller with a birth weight 20% less than the recipient’s birth weight.
Twin to twin transfusion syndrome or TTTS is also known as Feto-fetal transfusion syndrome and Twin Oligohydramnios-Polyhydramnios Sequence.
About 5-38 % of monochoriotic twins are reported to develop twin to twin transfusion syndrome in different studies.
Monozygotic twins occur in 3-5 per 1000 pregnancies and about 75% of monozygotic twins are monochorionic. Only monochorionic twins are at risk for TTTS.
Pathophysiology of Twin to Twin transfusion Syndrome
Twin to twin syndrome is the result of transfusion of blood from one fetal twin to another twin. As they share a single placenta, the blood supplies can become connected.
The blood transfusion from the donor twin to the recipient twin occurs through placental vascular anastomoses.
It results in low blood supply to donor twin [hypoperfusion] and hyperperfusion of the recipient twin.
The donor twin becomes hypovolemic and anuric [no passage of urine] and develops oligohydramnios.
Severe oligohydramnios can results in the stuck twin phenomenon in which the twin appears in a fixed position against the uterine wall. Ultrasonography cannot visualize the fetal bladder because of absent urine.
The recipient twin becomes hypervolemic and polyuric and leads to polyhydroamnios.
Either twin can develop hydrops fetalis. The donor because of anemia and high-output heart failure. The recipient because of hypervolemia.
After birth, the recipient twin can develop hypertension, hypertrophic cardiomegaly, disseminated intravascular coagulation, and hyperbilirubinemia.
TTTS usually develops during the period of peak placental growth[16-25 weeks].
Intrauterine death of one twin can lead tIntrauterine demise of one twin can result in neurologic sequelae in the surviving twin. Acute exsanguination of the surviving twin into the relaxed circulation of the deceased twin can result in intrauterine CNS ischemia.
Stages of Twin to Twin Syndrome
A small amount of amniotic fluid (oligohydramnios) is found around the donor twin and a large amount of amniotic fluid (polyhydramnios) is found around the recipient twin.
In addition to above, the ultrasound is not able to identify the bladder in the donor twin.
Findings of stages I and II+ Abnormal blood flow in the umbilical cords of the twins.
In addition to all of the above findings, the recipient twin has swelling under the skin and appears to be experiencing heart failure (fetal hydrops).
In addition to all of the above findings, one of the twins has died. This can happen to either twin. The risk to either the donor or the recipient is roughly equal.
The Quintero staging does not provide information about prognosis.
Affected women frequently complain of a rapidly enlarging abdomen over 2-3 weeks. Other complaints include preterm labor and premature rupture of membranes.
Twin to twin transfusion syndrome should be considered in a pregnant woman carrying monochorionic twins if she develops a rapidly increasing fundal height.
After birth, it can be considered if the twins are monozygotic, and there are significant differences occur in the size or appearance.
Donor twins are small for gestational age, pale and have poor peripheral perfusion
Recipient twins are large for gestational age, plethoric and have jaundice.
Hydrops fetalis can be present in either twin. These infants have subcutaneous edema, a distended abdomen, and respiratory distress.
In a newborn child following diagnoses may be considered.
- Hydrops fetalis
- Polycythemia of the newborn
- Anemia of the newborn
Newborn work up should include
The donor twin is frequently anemic whereas the recipient twin is frequently polycythemic at birth.
Hypocalcemia is frequently present in the donor twin.
Blood sugar levels are decreased in either twin.
To know presence of renal malfunction which can occur in either twin
Decreased platelet count can occur in either twin.
Hyperbilirubinemia may develop in the polycythemic recipient twin.
- Significant discrepancy in fetuses of same-sex
- Monochorionic placentation
- Significant disparity in the amount of amniotic fluid between the fetuses with oligohydramnios in smaller one
- Smaller fetus has absent stomach and bladder
- Intraventricular hemorrhage and periventricular leukomalacia in brain due to ischemia.
- Heart may show dysfunction, myocardial hypertrophy, valvular insufficiency, and pericardial effusions in either twin.
- Kidneys may show hypoxic-ischemic cortical necrosis.
- Ascites may be present if hydrops fetalis occurs.
Chest x-ray may show pleural effusions and cardiomegaly in hydrops fetalis.
Nutritional supplementation with dietary supplements during pregnancies has been reported to reduce the severity and incidence of twin to twin transfusion syndrome.
Amnioreduction can be done immediately once the diagnosis of twin to twin transfusion syndrome is made. This can be performed by placing a 20- or 18-gauge spinal needle into the amniotic cavity of the fetus with polyhydramnios under ultrasonographic guidance.
Repeat amnioreductions on recurrence of polyhydroamnios if earlier procedure had resulted in improvement in donor amniocentesis.
Fetoscopic Laser Photocoagulation of the Placenta
This is indicated if there is no response to amnioreduction or there is ca, cardiac hypertrophy or hydrops fetalis.
The procedure is performed in a few centers around the world.
Medical care of twins after birth is directed toward problems related to prematurity, anemia, polycythemia, and hydrops fetalis.
Severely anemic donor twins may require packed RBC transfusions or partial exchange transfusions.
Polycythemic recipient twins may require partial exchange transfusion to lower serum hematocrit levels.
Newborns with hydrops fetalis may require mechanical ventilation, thoracocentesis, pericardiocentesis, and paracentesis.
Mild-to-moderate twin to twin transfusion syndrome is frequently associated with premature delivery. Severe variety has a 60-100% fetal or neonatal mortality rate.
Intrauterine death of one twin is associated with neurologic sequelae in 25% of surviving twins.
The more premature the twins are at birth, the higher the incidence of postnatal morbidity and mortality.