Twin anemia polycythemia sequence
Twin anemia polycythemia sequence (TAPS) is considered a variant of the twin to twin transfusion syndrome (TTTS).
Epidemiology
TAPS may occur spontaneously in up to 5% of monochorionic twins and may also develop after incomplete laser treatment in twin-to-twin transfusion syndrome cases .
Pathology
As with twin-to-twin transfusion syndrome, the underlying mechanism is thought to be abnormal placental vascular anastomoses, however, in TAPS the rate of transfusion is slow and therefore results in a gradual discordance of fetal hemoglobin, without the hormonal disbalance and subsequent liquor discordance seen in TTTS. One twin develops anemia and the other polycythemia.
Radiographic features
Antenatal ultrasound
One of the features suggesting the diagnosis is a discordance in fetal middle cerebral artery peak systolic velocity (MCA-PSV) measurements . In contrast to the classic twin-to-twin transfusion syndrome, there is no amniotic fluid discordance (i.e. no-twin oligo-polyhydramnios sequence (TOPS)) .
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