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Seeing Red

The importance of twin anemia polycythemia sequence screening for parents.

Imagine there is a new disease out there that affects 1 in 20 babies before they are born. 

This disease can cause complications before birth, where the baby’s blood flow is affected, and they can be born needing urgent blood work done.  There is a risk of these babies having strokes or forming blood clots in utero, cutting off circulation to developing limbs. 

There’s also a risk of these babies sometimes having heart issues or other serious complications, and a high chance these babies will die before or just after birth because their bodies can’t cope with the associated problems.

TAPS twins

More often than not, these babies will be born prematurely, meaning extended hospital stays. Then there are all the problems associated with being born too soon, including the financial, psychological, and emotional implications to consider here too. It doesn’t stop at birth, though. This disease can also cause longer-term problems. 1 in 8 of these babies will be born profoundly deaf, and around 30 per cent will have cognitive delays or severe neurological impairment.  

Now imagine there is a test that can be done before birth to detect this disease. Imagine too, that dedicated researchers have spent over a decade researching the long-term effects and how to treat this disease. While there is no consensus on the best treatment, there are several options.

But often, parents are not told of this disease, or the fact that it exists, simply because the medical community feels it is too controversial, and there isn’t enough research. Medical guidelines intended to protect families neglect to routinely screen for this disease. As a result, around half of cases of this disease are usually found after the baby is born or when the baby becomes too sick in utero and dies before birth.

Even with more than a decade and a half of research, and despite being a simple, routine test, the establishment will not change their minds and update screening to support actively looking for this disease.   Parents are not informed about the risk of this disease, and if it is found, treatments and long-term outcomes are not discussed with them. Children are not followed up, or if they are, their parent’s concerns are dismissed or put down to overthinking.

It’s just stated there’s not enough research, that there’s no ‘best treatment’, and that they couldn’t do anything anyway. Families are left wondering and sometimes grieving for what could have been.

Now let’s stop imagining—this wouldn’t happen in a modern age. This would be unethical, and the wider community would be up in arms about neglect. Patients have the right to be informed about screening, treatments, and outcomes. This could not happen in modern times— right?

Sadly, in a small sub-group of babies, this is an actual situation. And what make this even more distressing is that very few people are talking about this, and even fewer people in the wider community are even aware that this is happening.

Twin anemia polycythemia sequence : TAPS

Described above is an overview of the current situation for patients diagnosed with twin anemia polycythemia sequence, or TAPS (Lopriore, et al., 2006),  as it’s better known.  This rare disease affects twins sharing a placenta (statistically, this type of twinning occurs in around 3 in 1,000 pregnancies.)  There is a hypothesis that the incidence rate is much higher; however, exact numbers are uncertain due to a lack of screening and diagnosis. (Slaghekke, et al., 2010)

While this is a rare disease and affects only a small population, less than five pairs in every 100 pairs of identical twins, rather than the larger group implied in the opening paragraph, the remaining points are frighteningly accurate.

In TAPS, the shared placenta of the twins has connecting blood vessels (Couck & Lewi, 2016).  One directional blood vessels, less than a millimetre thick, transfer red blood cells from one twin (the donor) to the other twin (the recipient.)  Donor twins become anemic slowly over time. The recipient twin’s blood becomes viscous and harder to push around the body due to excess red blood cells (Verbeek, et al., 2017).

Over time, the babies can become seriously ill.  As the disease advances, the risk of death of one or both twins increases.  They are generally born prematurely, which carries its own additional risks.

Donor twins are incredibly vulnerable, and one in eight are born deaf.  Both twins are also at risk of neurological complications, meaning that this disease can have a life-long impact.

The physical, emotional, psychological, and financial toll on families with a TAPS diagnosis can be devastating.

A controversial diagnosis

The controversy for this disease lies within screening and treatment.  TAPS has been researched for the past 15 years. As the disease has become more understood, staging systems and diagnostic criteria are incredibly refined. (Tollenaar L. , et al., 2021)

Using the speed blood flows through the babies’ brains to determine the presence of anemia is used accurately in screening for other fetal diseases. Proof also exists that it is also the most accurate way for detecting if TAPS is present in twin pregnancies. (Mari, et al., 2000)

While there is no “best” treatment, treatment options such as laser surgery, transfusions, and premature delivery, to name a few, have been proposed. These have been met with moderate success and led to establishing an international clinical trial to determine the most effective treatment (The TAPS Trial, 2020).

There is mounting evidence about this disease’s potentially devastating long-term consequences (Tollenaar L. , et al., 2019).  We have a deeper understanding of the pathogenesis and outcomes for TAPS twins and on their diagnosis and management more than ever before. Yet, very few countries support routine screening for TAPS from any gestational age. Many overseeing bodies will not update their recommendations, even after over 15 years of research.  (Nicholas, Fischbein, Ernst-Milner, & Wani, 2021).

The lack of updated screening protocols for TAPS is failing these twins.

Parental rights

Parents are routinely not informed about the risks of TAPS. When by chance, it is diagnosed, they are given very little information and very little hope for any treatment or outcomes. There is little to no discussion over long-term effects. Essentially, there is minimal opportunity for parents and care providers to discuss all available options and make informed decisions as a team. (Nicholas, Fischbein, Aultman, & Ernst-Milner, 2019).

This raises a question: Is this ignorance, either by choice or by a lack of awareness of the existing research, or is it political? Whatever the why, this small group of children remain affected by a rare disease.  It is such a small population, but shouldn’t every baby and, by extension, every parent have the right to a diagnosis?  Parents need to be able to make informed decisions about their care based on all the information available.  But denying screening, not discussing treatment options, and not talking about long-term outcomes could almost be seen as neglecting a duty of care.  

There is also the argument that there is not enough research to support routine screening.  Some say more data is needed, and then we will know the best way to handle these pregnancies.  But we have 15 years’ worth of data and research.  We have treatments and diagnostic criteria, and whilst not perfect, these are reasonably reliable.   

In itself, this is also a paradox.  How can we gather more data on something when data is not actively sought? The introduction of screening for TAPS and creating more opportunities for centralised data collection like registries would resolve this issue.  Why push back against gathering essential data to clarify such a controversial diagnosis? It simply doesn’t align logically.

An argument exists within some circles over additional screening costs to families—further tests mean higher prices passed on to families through healthcare and insurance.  When do we stop prioritising budgets and start addressing the financial and emotional burdens that a lifelong disability can bring families? Why are we putting a price on the right to information and mental health? What right does the establishment have to decide what financial lengths families should go to, instead of the families themselves?

Why is there a push-back on life-saving screening, putting families in difficult situations and facing the potential loss of one or both babies? This small group deserves access to knowledge and treatment.

A need for change

There is an inherent need for change when looking after monochorionic twins. While it is not limited to including screening for TAPS, this is a priority issue.  Data shows that up to 63 per cent of TAPS cases are not diagnosed until birth, and that donor twins are at incredible risk of complications and death (Tollenaar L. , et al., 2021).

In some cases like amniocentesis, we screen for rarer diseases in a much more invasive way with more risks associated with it. (Vink, Fuchs, & D’Alton, 2012). Professionals emphasise the urgency of these tests so families can be informed and make short and long-term plans.  Yet, an inexpensive, non-invasive doppler test is denied as part of routine screening, putting babies and families at financial, physical, and emotional risk. This is supported by the fact TAPS screening with doppler ultrasound fits all the criteria set by Wilson-Jungner in validity and effectiveness. (Wilson & Jungner, 1968)

Stephanie Ernst Taps Support

It is a small population of children, but it does not mean that they are less valuable, less loved, or less wanted.  Families have the right to know about this rare disease and be told all available options and care protocols.

Anything less is failing these families and putting the lives of a very vulnerable population at risk.

It’s time to change screening for twins and change the perception of twins in general. Twin pregnancies already face many complications and many heartbreaking decisions. We must ensure these families are well cared for and well informed.

It starts with changing the perception of one rare disease and changing screening protocols worldwide.  This alone would save lives. It’s about raising awareness and continuing to give the best possible standard of care to these children, from diagnosis to delivery and beyond.

We have to stop failing twins. Mortality rates are already high in multiple births. The risks and complications are real, and the long-term impact on their development is recorded (Khalil, Townsend, Reed, & Lopriore, 2021). We need to take action and recognise that there is an urgent need to review and change the way we see and treat multiple births.

It’s the right thing to do.  It will change lives.

To learn more about TAPS and access support please click on the logo or social icons.


(2020). Retrieved from The TAPS Trial:

Couck, I., & Lewi, L. (2016). The Placenta in Twin-to-Twin Transfusion Syndrome and Twin Anemia Polycythemia Sequence. Twin Research Human Genetics, 184-190. doi:10.1017/thg.2016.29

Khalil, A., Townsend, R., Reed, K., & Lopriore, E. (2021). Call to action: long-term neurodevelopment in monochorionic twins. Ultrasound in Obstetrics and Gynecology, 5-10. doi:10.1002/uog.23591

Lopriore, E., Middeldorp, J., Oepkes, D., Kanhai, H., Walther, F., & Vandenbussche, F. (2006). Twin Anemia–Polycythemia Sequence in Two Monochorionic Twin Pairs Without Oligo-Polyhydramnios Sequence. Placenta, 47-51. doi:10.1016/j.placenta.2006.01.010

Mari, G., Deter, R., Carpenter, R., Rahman, F, Zimmerman, R., . . . Blackwell, S. (2000). Non-invasive diagnosis by Doppler ultrasonography of fetal anemia due to maternal red-cell alloimmunisation. Collaborative Group for Doppler Assessment of the Blood Velocity in Anemic Fetuses. New England Journal of Medicine, 9-14. doi:10.1056/NEJM200001063420102

Nicholas, L., Fischbein, R., Aultman, J., & Ernst-Milner, S. (2019). Dispelling Myths about Antenatal TAPS: A Call for Action for Routine MCA-PSV Doppler Screening in the United States. Journal of Clinical Medicine, 977. doi:10.3390/jcm8070977

Nicholas, L., Fischbein, R., Ernst-Milner, S., & Wani, R. (2021). Review of International Clinical Guidelines Related to Prenatal Screening during Monochorionic Pregnancies. Journal of Clinical Medicine, 1128. doi:10.3390/jcm10051128

Slaghekke, F., Kist, W., Oepkes, D., Pasman, S., Middeldorp, J., Klumper, F., . . . Lopriore, E. (2010). Twin Anemia-Polycythemia Sequence: Diagnostic Criteria, Classification, Perinatal Management and Outcome. Fetal Diagnosis and Therapy, 181-190. doi:10.1159/000304512

Tollenaar, L., Lopriore, E., Oepkes, D., Haak, M. C., Klumper, F., Middeldorp, J., . . . Slaghekke, F. (2021). Twin Anemia Polycythemia Sequence: Knowledge and Insights After 15 Years of Research. Maternal Fetal Medicine, 33-41. doi:10.1097/FM9.0000000000000065

Tollenaar, L., Lopriore, E., Slaghekke, F., Oepkes, D., Middeldorp, M., Klumper, F., . . . van Klink, J. (2019). High risk of long-term neurodevelopmental impairment in donor twins with spontaneous twin anemia–polycythemia sequence. Ultrasound in Obstetrics & Gynecology, 39-46. doi:10.1002/uog.20846

Verbeek, L., Slaghekke, F., Sueters, M., M. J., Klumper, F., Haak, M., . . . Lopriore, E. (2017). Hematological disorders at birth in complicated monochorionic twins. Expert Review Of Hematology, 525-532. doi:10.1080/17474086.2017.1324290

Vink, J., Fuchs, K., & D’Alton, M. (2012). Amniocentesis in twin pregnancies: a systematic review of the literature. Prenatal Diagnosis, 409-416. doi:10.1002/pd.2897

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