OUR LETTER TO PARENTS
Diagnosed with TAPS
Being pregnant with monochorionic twins is so extra special that your babies just need extra special care. We can help you provide that for your babies,
TAPS (twin anemia polycythemia sequence) is a chronic (slow over time) form of TTTS. It is defined as where red blood cells from one baby (the donor) pass through very small shared blood vessels (less than 1cm in size and usually always artery to vein connections on the edge of the placenta), also called anastomoses, in a single monochorionic placenta, to the other baby (the recipient).
This creates a large hemoglobin difference between the babies with the donor baby’s blood like pink colored water and the recipient baby’s blood thick and sluggish like ketchup. Arteries are blood vessels that carry oxygen from the heart to the rest of the body. Veins are blood vessels that carry the blood back to the heart.
Unlike classic TTTS where one baby gets too much and too little “volume” of blood (causing more than normal and less than normal amounts of amniotic fluid), TAPS is an intertwin exchange through the placenta of only the red blood cells so the amniotic fluid levels stay normal and there is no physical changes in the mother, but TAPS can be life-threatening for the babies without anyone ever knowing.
You must get MCA dopplers in the brains of the babies to diagnose or rule out TAPS starting weekly at 16 weeks gestation through delivery of your babies.
Being pregnant with monochorionic twins is so extra special that your babies just need extra special care. We can help you provide that for your babies,
TAPS is a silent killer as the mother will not show any physical symptoms. Taps can happen before birth (antenatal) or after birth (postnatal). To diagnose (or rule out) TAPS, a high risk doctor called an MFM (maternal-fetal medicine) specialist will use a doppler to measure the peak systolic velocity (PSV), or the speed of blood flow, through the middle cerebral artery (MCA) of the brains of the babies (using a MCA-PSV Doppler).
The speed of the blood flow is measured by centimeters per second compared to the multiple of median (MOM) or the average speed for a baby at that particular gestation age. You want to see the measurement close to 1 for each baby. The further away from 1 the babies are (in opposite directions), the more serious the condition.
Once you have a measurement in centimeters per second (cm/sec), you can use this calculator to convert to the MOM measurement or this calculator adjusts for single vs. twin readings if give the measurement in centimeters per second (cm/sec), inches per minute (in/min) or millimeters (mm/min) per second, use this calculator to convert to the MOM.
The shared vessels in the monochorionic placenta that causes TAPS are extremely small, <1mm in size and are usually always artery to vein vessels. Imagine a strand of yarn (a shared vessel that causes TTTS) next to a strand of dental floss (a shared vessel that causes TAPS). There is increased red blood cells to the recipient, but not an increase in the volume of blood like in TTTS, so there is no increase in urine or polyhydramnios (amniotic fluid).
Fetoscopic demonstration of twin anemia polycythemia sequence (TAPS). Note the discordance in skin color between the reddish polycythemic twin in the near field and the pale anemic twin. Courtesy of Ramen Chmait, Medical Advisory Board Member of The TTTS Foundation.
TAPS can happen spontaneously (out of the blue all by itself) or after laser surgery called Post Laser TAPS (which is more common) when very small shared vessels (1mm in size usually at the edge of the placenta) are missed by the laser doctor. TAPS vessels are usually always artery to vein vessels.
A mom pregnant with monochorionic twins must get weekly ultrasounds from 16 weeks through delivery to look for TAPS as well as TTTS, SIUGR and rule out TRAP when everything is perfect in the pregnancy. In fact, a doctor may tell you the babies look great on ultrasound, which is wonderful to rule out TTTS, SIUGR and TRAP, but did the doctor do an MCA Doppler? If not, then things might not be so perfect.
TAPS should never be a surprise as it progresses very slowly. It can be diagnosed with an MCA doppler and if the numbers show TAPS, then monitors with an MCA doppler more frequently, 2-3 times a week or more depending on the severity. There is zero excuse by any doctor not to do an MCA Doppler and you must demand this or you need to switch doctors. The TTTS Foundation can help you get the care you need.
Babies born with untreated TAPS will show extreme differences in their coloring with the TAPS donor baby extremely white and pale from the severe anemia and the TAPS recipient baby extremely red to purple from the extreme overload of red blood cells.
The babies may need a blood transfusion for the anemic twin and partial transfusion to dilute the blood of the polycythemia twin. Since Acute TTTS can also take place at delivery with similar coloring, TAPS must be diagnosed by combination of placental analysis, hemoglobin levels of both twins and reticulocyte counts of each baby.
After birth, three criteria must be shown including: placental analysis of <1cm blood vessels, a difference of hemoglobin levels starting at >8 and difference of reticulocyte levels >1.7.
A placental pathologist will inject color into the monochorionic placenta and will be able to identify the very small blood vessels <1cm in size to confirm TAPS. With TTTS, the connecting blood vessels are much larger in size (dental floss compared to yarn). There will also be a color difference on the maternal side of the placenta (pale and dark) with TAPS that is not there with acute TTTS.
With TAPS, there is a large hemoglobin difference between the babies. Below are the Leiden Stages for hemoglobin levels for TAPS babies after birth after subtracting their individual levels.
Difference between the hemoglobin levels between the babies is:
For example, with Acute TTTS, there is a sudden sharing of more than normal amounts of blood volume to the recipient and less than normal amounts of blood volume to the donor, but the donor baby’s reticulocyte levels do not increase because it happened so quickly.
With TAPS, the anemic donor baby’s reticulocyte levels would be increased because TAPS is a slow, chronic disease with chronic blood loss and there would be time for a significant increase of the donor’s reticulocyte count compared to the other recipient baby.
The donor baby has severely lost red blood cells and young red blood cells (reticulocytes) are high to start to try and compensate. The recipient baby’s red blood cells are extremely high so the young blood cells (reticulocytes) are very low.
Recipient Baby: High blood cells, low reticulocytes Donor Baby: Low blood cells, high reticulocytes
To prove TAPS with reticulocyte levels, divide the reticulocyte count of the donor by the reticulocyte count of the recipient and that number should be >1.7.
Stage 1
Stage 2
Stage 3
Stage 4
Stage 5
If TAPS is suspected, your MFM should monitor and watch closely for a clear change in the MCA readings. If TAPS is spontaneously diagnosed, no prior laser surgery, laser surgery will be offered typically in stages 3-4 when there are signs of a compromised cardiovascular system and abnormal blood flow patterns in the umbilical cords. Delivery is always an option if symptoms are worsening and laser surgery is not available.
Laser Surgery
If TAPS is diagnosed after an incomplete laser surgery for TTTS, laser surgery can be repeated so as to analyze the placenta a second time to identify and to cauterize any small vessels <1cm that were missed during a first laser procedure.
Intraperitoreal Blood Transfusions
To help the donors anemia, this type of blood transfusion may be performed to allow a slow absorption of red blood cells into the babies’ share circulations. This approach protects the recipient baby from sudden blood loss. In the NICU, they will stabilize the babies
After Birth of the Babies
In the NICU, they will stabilize the babies through a partial exchange transfusion for the recipient to decrease the thickness of the blood, and a blood transfusion for the anemic donor baby.
In summary, you must have MCA dopplers on the brain of the babies done weekly while you also are looking for TTTS starting by 16 weeks. The doctor might also see the TAPS donors’ side of the placenta thicker and lighter in color than the other baby’s side. They might also see a starry liver in the recipient of white dots on the liver like multiple stars in the sky.
Brandon and Laura’s babies Summer and Lee had TTTS laser surgery only to find out the babies were then diagnosed with TAPS. Summer and Lee are the babies featured at the top of this section. To see them improve from being red to purple and white to just beautiful, healthy little girls is an inspiration for everyone to keep fighting and contact The TTTS Foundation for help.