Stages of TTTS

Staging of TTTS based on Sonographic and Doppler Findings

TTTS is staged in an effort to offer the most appropriate treatment for the level of disease present. Surgery may not be indicated in all cases.

Stage I
There is a small amount of amniotic fluid in the donar twins sac (known as oligohydramnios) and a large amount of amniotic fluid (polyhydramnios) in the recipient's sac. At this stage, surgery may not be indicated but close observation for a change in condition is recommended.

Stage II
Along with poly / oligohydramnios, there is no visible bladder in the donor. At this stage, laser surgery is recommended.

Stage III
Characterized by Critically Abnormal Dopplers (CADs), which means one of the babies has poor blood flow. Laser Surgery is offered for this stage. If laser surgery is not possible, umbilical cord ligation may be performed if absolutely necessary.

Stage IV
All of the above findings are present and the baby is hydropic. This means there is swelling of the head and abdomen (ascites), the heart contracts poorly, and heart failure is present. The natural history of this disease has shown that at this stage a baby is not likely to survive or will suffer from heart disease in life.

Stage V

Demise / Death
* Critically Abnormal Dopplers, defined as the presence of at least one of the following:
a) Absent or reverse end diastolic velocity in the umbilical artery (AEDV/REDV)
b) Reverse flow in the ductus venosus (RFDV), or
c) Pulsatile umbilical venous flow (PUVF) www.fetalmd.com

One classification scheme separates TTTS into severe, moderate, and mild.

Severe TTTS presents early in the second trimester at 16-18 weeks' gestation. A difference exists in fetal size of twins who are more than 1.5 weeks gestation. Umbilical cord sizes differ between the twins. Hemoglobin concentrations usually are the same in both twins because the transfusion is a whole blood shift. Polyhydramnios develops in the sac of the recipient twin because of volume overload and increased fetal urine output. Oligohydramnios develops in the sac of the donor twin because of hypovolemia and decreased urine output. Severe oligohydramnios can result in the stuck twin phenomena in which the twin appears in a fixed position against the uterine wall.

Moderate TTTS develops later in the second trimester between 24-30 weeks gestation. Although a fetal size discrepancy exists at more than 1.5 weeks gestation, polyhydramnios and oligohydramnios do not develop. The donor twin becomes anemic, hypovolemic, and growth is retarded. The recipient twin becomes plethoric, hypervolemic, and macrosomic. Either twin can develop hydrops fetalis. The donor twin can become hydropic because of anemia and high-output heart failure. The recipient twin can become hydropic because of hypervolemia. The recipient twin also can develop hypertension, hypertrophic cardiomegaly, disseminated intravascular coagulation, and hyperbilirubinemia after birth.

Mild TTTS develops slowly in the third trimester. Polyhydramnios and oligohydramnios usually do not develop. Hemoglobin concentrations differ by more than 5 g/dL. Twin size differs by more than 20%. Acute TTTS can occur at birth during the time between clamping the umbilical cords of the first and second twin. During this interval, the second twin has sole connection to the placenta and may receive a significant transfusion of blood.