How is TTTS diagnosed?
The diagnosis of Twin-to-Twin Transfusion Syndrome (TTTS) is made when the ultrasound reveals one twin (donor) to have an abnormally low level of amniotic fluid while the other twin (recipient) has 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.
Is it mild or severe?
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.
Stages of TTTS
TTTS is divided into different stages, 1 through 5, to determine when to begin medical intervention and what method to use.
Stage I is generally considered the minimum criteria to technically be diagnosed with TTTS. If there are no concerns about pre-term labor, medical 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 two weeks and more frequently if there are any concerns.
Stage 2 results 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. Medical intervention is recommended, as TTTS Stage 2 does not often improve on its own.
Stage 3 is reached 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 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.