Twin-to-twin transfusion syndrome
| Twin-to-twin transfusion syndrome | |
|---|---|
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| Illustration of a Fetoscopy and laser ablation of connecting vessels in Twin-to-twin transfusion syndrome | |
| Classification and external resources | |
| Specialty | pediatrics |
| ICD-10 | O43.0, P02.3, P50.3 |
| ICD-9-CM | 762.3 , 772.0 |
| DiseasesDB | 32064 |
| MedlinePlus | 001595 |
| eMedicine | med/3410 |
| MeSH | D005330 |
| Orphanet | 95431 |
Twin-to-twin transfusion syndrome (TTTS), also known as Feto-Fetal Transfusion Syndrome (FFTS) and Twin Oligohydramnios-Polyhydramnios Sequence (TOPS) is a complication of disproportionate blood supply, resulting in high morbidity and mortality. It can affect monochorionic multiples, that is, multiple pregnancies where two or more fetuses share a chorion and hence a single placenta. Severe TTTS has a 60–100% mortality rate.
As a result of sharing a single placenta, the blood supplies of monochorionic twin fetuses can become connected, so that they share blood circulation: although each fetus uses its own portion of the placenta, the connecting blood vessels within the placenta allow blood to pass from one twin to the other. It is thought that most monochorionic placentae have these "shared connections" that cross the placenta, with the net flow volumes being equal between them. This state is sometimes referred to as "flow balance". Depending on the number, type and direction of the interconnecting blood vessels (anastomoses), blood can be transferred disproportionately from one twin (the "donor") to the other (the "recipient"), due to a state of "flow imbalance" imparted by new blood vessel growth across the placental "equator", the line that divides each baby's proportion of the shared placenta. This state of transfusion causes the donor twin to have decreased blood volume, retarding the donor's development and growth, and also decreased urinary output, leading to a lower than normal level of amniotic fluid (becoming oligohydramnios). The blood volume of the recipient twin is increased, which can strain the fetus's heart and eventually lead to heart failure, and also higher than normal urinary output, which can lead to excess amniotic fluid (becoming polyhydramnios).
TTTS usually develops during the period of peak placental growth, starting in week 16 and proceeding through week 25; after this point, the placenta's growth decelerates, essentially stopping just after week 30. While TTTS has occasionally been detected beyond this timepoint, it is thought that its occurrence beyond week 30 may be due to a placental embolism that upsets the flow balance of the shared connections between the babies. TTTS is potentially lethal to either or both twins, no matter when it is detected. However, when detected past week 25, emergency delivery may be considered to rescue the babies if the TTTS is severe.
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Wikipedia