Twin Anemia Polycythemia Sequence: Current Views on Pathogenesis, Diagnostic Criteria, Perinatal Management, and Outcome

Abstract

Monochorionic twins share a single placenta and are connected with each other through vascular anastomoses. Unbalanced inter-twin blood transfusion may lead to various complications, including twin-to-twin transfusion syndrome (TTTS) and twin anemia polycythemia sequence (TAPS). TAPS was first described less than a decade ago, and the pathogenesis of TAPS results from slow blood transfusion from donor to recipient through a few minuscule vascular anastomoses. This gradually leads to anemia in the donor and polycythemia in the recipient, in the absence of twin oligo-polyhydramnios sequence (TOPS). TAPS may occur spontaneously in 3-5% of monochorionic twins or after laser surgery for TTTS. The prevalence of post-laser TAPS varies from 2% to 16% of TTTS cases, depending on the rate of residual anastomoses. Pre-natal diagnosis of TAPS is currently based on discordant measurements of the middle cerebral artery peak systolic velocity (MCA-PSV; >1.5 multiples of the median [MoM] in donors and <1.0 in recipients). Post-natal diagnosis is based on large inter-twin hemoglobin (Hb) difference (>8 g/dL), and at least one of the following: reticulocyte count ratio >1.7 or minuscule placental anastomoses. Management includes expectant management, and intra-uterine blood transfusion (IUT) with or without partial exchange transfusion (PET) or fetoscopic laser surgery. Post-laser TAPS can be prevented by using the Solomon laser surgery technique. Short-term neonatal outcome ranges from isolated inter-twin Hb differences to severe neonatal morbidity and neonatal death. Long-term neonatal outcome in post-laser TAPS is comparable with long-term outcome after treated TTTS. This review summarizes the current knowledge after 10 years of research on the pathogenesis, diagnosis, management, and outcome in TAPS.

The value of echocardiography and Doppler in the prediction of fetal demise after laser coagulation for TTTS: A systematic review and meta‐analysis

“…In monochorionic twins, unbalanced net intertwin blood transfusion may lead not only to TTTS but also to twin anemia polycythemia sequence (TAPS). In TAPS, there is a chronic and slow transfusion of blood from the donor to the recipient twin through extremely small anastomoses . This process leads to an anemic donor and polycythemic recipient.…”

Risk factors for fetomaternal bleeding after laser therapy for twin‐twin transfusion syndrome

“…Interestingly, in a study by Robyr et al, the rate of post‐laser TAPS was 13% overall, with 69.3% of cases occurring in TTTS Quintero Stage III . TAPS after laser surgery for TTTS has been reported to occur in 2% to 16% of cases . We posit that the etiology for both higher rates of positive post‐laser KB tests and postoperative TAPS may be, at least in part, associated with a common intrinsic pathophysiological derangement of TTTS stage III‐R or III‐RD.…”

Role of ultrasonography in the management of twin gestation

“…Treatment is dependent on gestational age, but can include continued observation, intrauterine fetal transfusion, sFLP, or delivery with postnatal treatment . Currently, the best treatment for TAPS has not been established …”