science

Twin anemia-polycythemia sequence

Twin anemia-polycythemia sequence is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Twin anemia-polycythemia sequence rather than just read about it. In short: Twin anemia-polycythemia sequence (TAPS) is a chronic type of unbalanced fetal transfusion in monochorionic twins that results in polycythemia in the TAPS recipient and anemia in the TAPS donor due to tiny placental anastomoses. Post-laser TAPS and spontaneous TAPS are the two forms of TAPS.

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Reference excerpt

Twin anemia-polycythemia sequence (TAPS) is a chronic type of unbalanced fetal transfusion in monochorionic twins that results in polycythemia in the TAPS recipient and anemia in the TAPS donor due to tiny placental anastomoses. Post-laser TAPS and spontaneous TAPS are the two forms of TAPS. Unlike twin-to-twin transfusion syndrome, which arises when twin oligohydramnios polyhydramnios sequence (TOPS) is present, TAPS develops in its absence.

Signs and symptoms A pale, anemic donor and a plethoric, polycythemic recipient make up the traditional clinical picture of TAPS. In 29% of spontaneous TAPS twins and 23% of post-laser TAPS twins, severe fetal growth restriction is present.

Causes The cause of TAPS is slow and persistent unbalanced feto-fetal transfusion through tiny placental anastomoses, which progressively results in highly discordant hemoglobin levels. This causes the recipient twin to become polycythemic and the donor twin to become anemic.

Mechanism There are very few, tiny arteriovenous vascular anastomoses present in TAPS placentas. This distinct angiography is the foundation of the pathogenesis of TAPS. A slow transfusion of blood from the donor to the recipient is made possible by the few tiny anastomoses, which eventually cause very disparate hemoglobin levels. It's unclear if hormonal dysfunction may also contribute to the onset of TAPS.

Diagnosis Doppler ultrasound abnormalities demonstrating an increased peak systolic velocity in the middle cerebral arteries (MCAPSV) in the donor twin and a decreased MCA-PSV in the recipient twin can be used to make an antenatal diagnosis of TAPS. The presence of polycythemia in the recipient and (chronic) anemia in the donor, along with characteristic placental angioarchitecture as determined by injection with colored dye, are the basis for the postnatal diagnosis of TAPS.

Classification

Prevention The rate of residual anastomoses can be decreased to prevent postlaser TAPS. The "Solomon technique," an alternate method of laser surgery, may help lower the possibility of omitting a tiny anastomosis during the procedure.

Treatment Weekly ultrasound monitoring, which includes a full staging Doppler examination with the MCA-PSV, is part of the expectant management protocol. The recent onset of ultrasound abnormalities may require an increase in the surveillance frequency. When TAPS patients present in the first or early second trimester, this approach is preferred because many of these patients may resolve or remain clinically stable. Expectant care can be continued with the aim of achieving a late preterm delivery in stable cases that do not advance past stage 2. It is necessary to take into account alternate management options if TAPS is accelerating. Treatments that are temporary include intrauterine blood transfusion of the anemic donor twin or exchange transfusions, which remove blood from the recipient twin and then transfusion of the donor. Treating TAPS with fetal laser coagulation of vascular anastomoses is the only potentially effective modality.

Outlook In the TAPS Registry cohort, 11% of post-laser TAPS twins and 5% of spontaneous TAPS twins experienced spontaneous fetal death.

Epidemiology Postlaser TAPS can occur in 2–13% of cases, depending on the definitions and criteria applied. The range of incidence for spontaneous TAPS is 3–5%.

See also Twin-to-twin transfusion syndrome Monochorionic twins

Notes

References

Further reading Khalil, A.; Gordijn, S.; Ganzevoort, W.; Thilaganathan, B.; Johnson, A.; Baschat, A. A.; Hecher, K.; Reed, K.; Lewi, L.; Deprest, J.; Oepkes, D.; Lopriore, E. (2020). "Consensus diagnostic criteria and monitoring of twin anemia–polycythemia sequence: Delphi procedure". Ultrasound in Obstetrics & Gynecology. 56 (3): 388–394. doi:10.1002/uog.21882. hdl:1887/3185160. ISSN 0960-7692. PMID 31605505. Tollenaar, Lisanne S.A.; Prins, Sandra A.; Beuger, Sabine; Slaghekke, Femke; Oepkes, Dick; Lopriore, Enrico (2021). "Twin Anemia Polycythemia Sequence in a Dichorionic Twin Pregnancy Leading to Severe Cerebral Injury in the Recipient". Fetal Diagnosis and Therapy. 48 (4). S. Karger AG: 321–326. doi:10.1159/000514408. hdl:1887/3277471. ISSN 1015-3837. PMID 33774643.

External links The Children's Hospital of Philadelphia The Johns Hopkins University Taps Support Foundation Taps Support

Illustrations

Worked examples

Example 1 — a first encounter with Twin anemia-polycythemia sequence

Start with the simplest possible case. Write down what Twin anemia-polycythemia sequence claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Twin anemia-polycythemia sequence before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Twin anemia-polycythemia sequence ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Twin anemia-polycythemia sequence

In research: Twin anemia-polycythemia sequence appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Twin anemia-polycythemia sequence in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Twin anemia-polycythemia sequence is common in secondary-school and first-year university syllabi. It links to neighbouring topics Pathology of pregnancy, childbirth and the puerperium, Syndromes, Twin, so understanding it makes those chapters shorter.
In everyday life: Look for Twin anemia-polycythemia sequence outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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Frequently asked questions

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