Twin Anemia Polycythemia Sequence (TAPS) is a relatively rare but potentially severe fetal condition that occurs in monochorionic twin pregnancies.
TAPS is marked by a chronic imbalance in hemoglobin levels between the twins, with one twin becoming anemic (the donor) and the other polycythemic (the recipient).
The incidence of TAPS is estimated to be 3-5% in monochorionic twins and up to 13% following laser therapy for TTTS. This VISUOG chapter will cover the pathophysiology, diagnosis, and staging of TAPS.
TAPS is identified by significantly discordant middle cerebral artery (MCA) peak systolic velocities (PSV) between the twins. Unlike twin-twin transfusion syndrome (TTTS), TAPS does not usually present with the amniotic fluid discrepancies, making it harder to detect without specific screening. A five-stage classification system assesses the severity of TAPS and guides treatment decisions. The subtle presentation of the condition emphasizes the importance of regular and detailed ultrasounds in TAPS patients.
Management strategies for TAPS depend on the severity of the condition and the timing of diagnosis. Expectant management may be sufficient for mild cases, while more severe cases may require intrauterine fetal interventions, such as fetoscopic laser photocoagulation (FLP) or intrauterine transfusion (IUT), to correct the imbalance or prevent further progression.
This chapter is great in detailing prenatal diagnosis, including a summary of the different criteria used for the prenatal and postnatal diagnosis and staging of TAPS. The chapter continues to detail information including monitoring and screening, as well as management for TAPS; choice of strategy should be individualized based on gestational age, severity of TAPS, etiology of TAPS, and feasibility of intervention.
The chapter continues to discuss the prognosis for twins, which is affected by TAPS and varies widely, influenced by factors such as the severity of the condition, the timing of the diagnosis, and the chosen management strategy.
This chapter provides an in-depth look at prenatal diagnosis, summarising the criteria for both prenatal and postnatal diagnosis and staging of TAPS. It also covers monitoring, screening, and management strategies, emphasising that these should be individualised based on gestational age, severity, etiology, and intervention feasibility.
Additionally, the chapter discusses the prognosis for twins affected by TAPS, which varies widely depending on the severity of the condition, the timing of diagnosis, and the chosen management approach.
For more detailed information and to see high-quality ultrasound images and videos, read the VISUOG chapter on twin-anemia polycythemia sequence for free throughout September.
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