This year’s theme is #32Weeks – the average gestation for TAPS twins. However, we’ve compiled a list of 32 Facts about TAPS that every doctor, researcher, parent and friend of TAPS twins should know.
32 Facts About TAPS
- The very first paper, published on March 1st, 2006 describing a unique complication of TTTS laser surgery, reinforced the need for routine MCA dopplers to be performed on patients. This complication was caused by tiny, residual connections in the placenta, and left one baby anemic, the other polycythemic.
- A second, revolutionary paper was published. This paper described the same condition as happening spontaneously in monochorionic twins. When the placentas were examined, it was discovered that this was caused by tiny, one-way connections in the placenta. This paper also gave the disease a name: Twin Anemia Polycythemia Sequence, or TAPS.
- TAPS is not a form of TTTS. It’s a form of feto-fetal transfusion, just like TTTS is. However, they have different diagnostic criteria, different long term outcomes and different treatments before and after birth.
- TAPS has it’s own ORPHA code – 617294 designating it as a rare disease
- The average gestation for TAPS twins is just 32 weeks, putting them at risk of prematurity-related complications and the long-term effects of TAPS.
- It’s incredible to think that this problem is caused by just a few tiny connections in the placenta. Research has told us that this disease happens slowly, over a long period of time, and that the actual amount of blood transferred from donor to recipient over 1 day is around 5 milliliters at 29 weeks gestation. The average blood transfusion for a 1 kg baby is 15 milliliters.
- TAPS placentas differ from TTTS placentas due to the size of the connections. TTTS placentas have lots of large connections of all types (artery to artery, artery to vein, and vein to vein). TAPS placentas have a few small (less than 1mm) connections, and are mostly artery to vein. Artery to artery and vein to vein connections are less common.
- Spontaneous TAPS placentas and post-laser TAPS placentas also have differences when it comes to number of directions. Spontaneous TAPS placentas have more connections, that are spread out over the entire placenta. Post-Laser TAPS placentas usually have 1-2 small connections close to the edges, where it is easier to “miss” them after laser surgery.
- TAPS is feto-fetal transfusion that does not present with fluid differences. (TTTS, or TOPS, has these fluid differences – see why they’re different diseases?). However, they can co-exist and between 9-18% of TTTS cases will also have signs of TAPS. In these cases, the placentas also have fewer connections than with just TTTS.
- In spontaneous TAPS, around 50% of donor twins are severely growth restricted (<3rd percentile), compared to recipient twins (11%). This difference hasn’t been observed in post-laser TAPS. Spontaneous TAPS donor twins often have a larger placental share (in cases without FGR or TTTS) so it appears the size difference is caused by the blood transfusion.
- TAPS happens mostly in monochorionic, diamniotic twin pregnancies. However it has been recorded in monochorionic monoamniotic twins, and in a few rare instances, in dichorionic, diamoniotic twins. More research is needed.
- TAPS onset can be anywhere between 15 and 35 weeks. In post-laser TAPS, it is more likely to be recorded in the first month after surgery, but has been recorded up to 17 weeks post-surgery.
- It used to be thought that in post-laser TAPS, the donor and recipient would “switch places”. Newer research shows that this happens in only a little over half of cases (55%).
- MCA dopplers are still the most reliable way to detect TAPS, and the new staging system (using delta MCA-PSV with a difference of 0.5 as the cut off) is the most accurate. More research is needed to refine the staging system.
- It used to be all about MCA dopplers, but now we know that 86% of TAPS cases will show more than one other indicator of TAPS. 44% of cases will have a bright (echogenic) placenta for donors, 70% of donors will have cardiomegaly, and 66% of recipients will have a starry sky liver. While this is great news that we have other things to look for, it’s still vital to do MCA dopplers as 14% of TAPS cases will have nothing more than discordant dopplers.
- Treatment options are as follows. Expectant management (or watch and wait), early delivery after viability (as better out than in for treating anemia/polycythemia), IUT/PET – blood transfusions and exchanges in utero, Laser surgery with the Solomon technique, and selective reduction where one baby is reduced (usually the donor).
- There is no best treatment for TAPS yet. A recent international, multicentre trial found there were very few differences in outcomes for all management types. The TAPS Trial is ongoing to determine a best treatment option.
- Preventing post-laser TAPS: The Solomon technique has reduced the incidence of post laser TAPS in TTTS cases. No amount of protein drinks or bed rest can prevent TAPS
- Approximately 40% to 63% of TAPS cases are missed before birth. The current diagnostic criteria includes a difference of 8g/dL in hemoglobin between the babies. HOWEVER, as there are other conditions that present with the same symptom, it is vital that reticulocytes are also checked, and that the placenta is sent for dye injection.
- The TAPS placenta also has color differences on the maternal side. It’s important to flip it over and check for this as well as the correct diagnostic criteria
- TAPS and acute TTTS have different treatment options, and it is vital to test the babies correctly as the wrong treatment can be dangerous, or deadly.
- Spontaneous perinatal mortality occurs in 9% of spontaneous TAPS twins, and 18% of post-laser cases. Donor twins are at the highest risk, in spontaneous TAPS this is 12%, and in post laser cases, over a quarter (26%).
- In post-laser TAPS, the outcomes are similar to TTTS cases post laser surgery. There is an overall chance of severe neurodevelopmental impairment at a rate of 9% with no big difference between donors and recipients
- Severe NDI happens at a rate of 9% also, but this is where the similarities end. There is a big difference between donors (18% chance) and recipients (3% chance). Donors are also at a bigger risk of mild cognitive impairment (35% compared to 18%), and a lower rate of having no neurodevelopmental impairment (45% compared to 80% of recipients).
- Deafness in spontaneous TAPS donors: the type of deafness is specific and is called auditory neuropathy spectrum disorder. It is not clear what causes the deafness, but it is not recorded in TTTS donors or children born anemic from alloimmunization.
- TAPS is not a form of TTTS. It has a different pathogenesis, different timing of onset, different diagnostic criteria, different classification systems, and different short and long term outcomes. MCA dopplers are vital, but so is looking for the other signs of TAPS.
- Donor twins in TAPS are born with lower pH levels, and higher lactate levels meaning that they’re probably hypoxic during the pregnancy due to anemia.
- Donor twins are more likely to be born hypoglycemic, meaning neonatologists should be aware of this so the appropriate interventions can be made at birth, and monitored closely
- Long term followups are vital for monochorionic twins, in particular neurodevelopmental followups.
- Even after 17 years of research, TAPS screening is not supported worldwide, and many guidelines do not include it as part of routine care for monochorionic twins.
- There are still many myths and misconceptions about TAPS out there, even with the volume of research that exists.
- There has been already 1 major clinical trial into TAPS – The Solomon Laser Study, and one registry – The TAPS Registry. There is now the TAPS Trial, investigating the best treatment for TAPS.
- TAPS is not limited to the neonatal phase and more cooperation and collaboration is needed, as well as long term research.
While we chose 32 facts about TAPS ,there are so many more things to know. Join our international call to action on International TAPS day, and share your stories, your research, and most importantly, help us rais awareness of TAPS. Get in touch with us to find out how you can help. Feel free to use our 32 Facts About TAPS page as a resource.