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Introduction

Twin-to-twin transfusion syndrome (TTTS), also known as feto-fetal transfusion syndrome (FFTS), twin oligohydramnios-polyhydramnios sequence (TOPS) and stuck twin syndrome is a complication of disproportionate blood supply, resulting in high morbidity and mortality.

TTTS was first described by a German obstetrician, Friedrich Schatz, in 1875. Once defined by neonatal parameters—differences in birth weight and cord haemoglobin at the time of delivery—TTTS is now defined differently. Today, it is known that discordant foetal weights will most likely be a late manifestation, and foetal haemoglobin through cordocentesis is often equivalent in the twin pair even in severe TTTS.

It can affect monochorionic multiples, that is, multiple pregnancies where two or more foetuses share a chorion and hence a single placenta. Severe TTTS has a 60–100% mortality rate. The twin-to-twin transfusion syndrome (TTS) is a severe complication occurring in 5% of monochorionic twin pregnancies. This condition is thought to result from an unbalanced foetal blood supply through the placental vascular shunts, with the larger twin being the recipient and the smaller twin the donor. At an early stage, the disease is characterized by polyuria and polyhydramnios in the recipient foetus, whereas there is oliguria and, therefore, oligohydramnios in the donor.Major Polyhydramnios may cause extreme premature labour. Severe oligohydramnios results in the stuck twin phenomenon, a condition in which the donor appears tightly wrapped in his amniotic sac. In the most severe cases, the recipient may die from cardiac failure and the smaller twin from anaemia and hypoxia, or both twins may die as a result of premature labour. In either twin, severe ischemic brain damage may result from acute hemodynamic changes.

The exact cause of TTTS is not fully understood. However, it is known that abnormalities during division of the mother's egg after it has been fertilized lead to the placental abnormalities that can ultimately result in twin-twin transfusion syndrome.

A staging system is commonly used to classify the severity of TTTS.

Stage I: 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.

Stage II: In addition to the description above, the ultrasound is not able to identify the bladder in the donor twin.

Stage III: In addition to the characteristics of Stages I and II, there is abnormal blood flow in the umbilical cords of the twins.

Stage IV: In addition to all of the above findings, the recipient twin has swelling under the skin and appears to be experiencing heart failure (foetal hydrops).

Stage V: 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 & is quite high in Stage II or higher TTTS.

Various treatments for TTTS include:

No treatment -This is equivalent of zero intervention. It has been associated with almost 100% mortality rate of one or all foetuses. Exceptions to this include patients that are still in Stage 1 TTTS and are past 22 weeks' gestation.

Adjustment of amniotic fluid

· Serial amniocentesis

This procedure involves removal of amniotic fluid periodically throughout the pregnancy under the assumption that the extra fluid in the recipient twin can cause preterm labour, perinatal mortality, or tissue damage. In the case that the fluid does not reaccumulate, the reduction of amniotic fluid stabilizes the pregnancy. Otherwise, the treatment is repeated as necessary.

· Sept ostomy, or iatrogenic disruption of the dividing membrane

This procedure involves the tearing of the dividing membrane between foetuses such that the amniotic fluid of both twins mixes under the assumption that pressure is different in either amniotic sac and that its equilibration will ameliorate progression of the disease

Adjustment of blood supply

· Laser therapy

This procedure involves endoscopic surgery using laser to interrupt the vessels that allow exchange of blood between foetuses under the assumption that the unequal sharing of blood through these vascular communications leads to unequal levels of amniotic fluid. Each foetus remains connected to its primary source of blood and nutrition, the placenta, through the umbilical cord.

· Umbilical cord occlusion

This procedure involves the ligation or otherwise occlusion of the umbilical cord to interrupt the exchange of blood between the foetuses. The procedure is typically offered in cases where one of the foetuses is presumed moribund and endangering the life or health of the other twin through resultant hypotension.

Many cases of TTTS can't be prevented, but maintaining a healthy diet before and during pregnancy can help to prevent TTTS, or make it less severe if it does occur. Take prenatal supplements as recommended by your doctor. Always attend regular prenatal appointments to monitor your pregnancy