How is TTTS diagnosed?

The diagnosis of TTTS is made when the ultrasound reveals one twin (donor) to have an abnormally low level of amniotic fluid. The sonographer or physician may refer to this baby as "stuck" or "saran-wrapped".

In addition, the other twin (recipient) demonstrates an excessive amount of amniotic fluid.

Some pregnant women with TTTS notice a sudden change in the fullness or tightness of their belly and/or uterine contractions from the excessive amniotic fluid around the recipient twin.

How do you decide how bad the condition is?

TTTS can be mild or severe, depending on how the babies are affected.  Each case is unique in presentation as well as in the course of disease progression. 

TTTS has been divided into different stages to help determine when to intervene and by what method.

The stages of TTTS are identified as 1 through 5, cumulatively increasing in severity.

Stage I is generally considered the minimum criteria to technically be diagnosed with TTTS.  At this stage, the donor twin has oligohydramnios (a maximum vertical pocket of less than 2 cm) AND the recipient twin has polyhydramnios (a maximum vertical pocket of greater than 8-10 cm).

At this stage, if there are no concerns about pre-term labor, intervention is usually not recommended. However, the pregnancy should be closely monitored by a qualified Maternal-Fetal Medicine Specialist due to the unpredictable nature of the disease. TTTS can progress rapidly, stay stable or regress. All pregnancies at risk for TTTS should be monitored at least every 2 weeks and more frequently (sometimes even bi-weekly) if there are any concerns.

Stage 2 happens when the bladder in the donor twin is not visible during the course of the ultrasound exam.  This indicates that the bladder is empty and signals worsening dehydration of the donor twin. At this stage, intervention is recommended, as TTTS Stage 2 does not often improve on its own.

Stage 3 is identified when the blood flow patterns (Doppler studies) have become critically abnormal.  Blood flow patterns are measured in three areas of each twin;  the umbilical cord, the middle cerebral artery (a vessel in the brain) and the ductus venosus (a vessel near the liver). These measurements give the physician a sense of how each baby is tolerating the progression of TTTS.  This stage requires intervention by laser photocoagulation.

Stage 4 is reached when the recipient twin has developed swelling under the skin (hydrops) and appears to be in heart failure. This is situation is now critical and requires urgent intervention by Laser photocoagulation.

Stage 5 means that one of the twins has died. This can happen to either twin. Thorough ultrasound examination of the survivor is important to ensure that this baby has not been adversely affected. Sometimes an intrauterine fetal blood transfusion may help the survivor.