In 2006, a new, rare disease affecting monochorionic twins was identified and named. Twin Anemia Polycythemia Sequence (TAPS) changed the perception of the complications of monochorionic twins. It started redefining what we knew about shared placentas.
Shared Placentas – A Brief History.
In the 1800s, there was already a rudimentary understanding of the complications of monochorionic twins. Shared blood vessels in the placenta created imbalances and caused deadly complications. Twin to Twin Transfusion Syndrome is well described, and there are depictions of this throughout history. Large surface connections in the placenta cause TTTS. Until the last decade, any size discordances or color differences were always considered to be caused by this disease.
Untreated, it was nearly always fatal or resulted in severe disabilities. In the 1980s, experimental laser surgery developed by Dr. Bernischke and Dr. DeLia was introduced, providing effective treatment. Over the last decades, this surgery has been refined to an art form and improving survival rates for babies with TTTS and bringing hope to families.
Twin Anemia Polycythemia Sequence – A New Diagnosis
In 2006, two papers were published within days of each other, blowing this theory out of the water. The first described a rare complication of laser surgery. Small residual connections in the placenta either missed by the laser or incompletely sealed caused one baby to become slowly anemic and the other polycythemic. This occurred in around 16% of TTTS cases after laser surgery.
The second paper described the same disease but happening spontaneously via small connections in the placenta. It also gave this new disease a name – Twin Anemia Polycythemia Sequence, or TAPS. TAPS is recorded in around 3-5% of monochorionic twin pregnancies
This new disease, a separate, distinct form of feto-fetal transfusion from Twin To Twin Transfusion Syndrome, shook the fetal therapy world with its arrival. It is a controversial diagnosis because there is no consensus on the best treatment for it. Unfortunately, this has also created many issues with introducing routine screening for spontaneous TAPS, as many believe it should not be screened for without an established therapy. This is despite severe long-term consequences like developmental delays and deafness in donor twins.
In most cases, TAPS is screened for after laser surgery but has a high mortality rate for donor twins, and some centers will not repeat the laser surgery. There is no established best treatment for TAPS, which causes many problems for families with a diagnosis.
The First Clinical Trial
In 2008, a new laser therapy technique was trialed to treat TTTS. Instead of selectively targeting the large connections in the placenta, this new technique drew a line across the vascular equator of the placenta, effectively separating it into 2. This technique was called the Solomon Technique (which stands for Selective Or complete Laser Occlusion in MONochorionic twins) and does have a biblical reference to the story of King Solomon.
This revolutionary laser therapy technique reduced the incidence of post-laser TAPS in the trial from 16% to just 3%. By drawing a line across the placenta with the laser, the chance of missing the tiny connections and incomplete ablation of the vessels is reduced significantly.
In 2014, it was hypothesized that this therapy could treat TAPS based on data collected between 2005 and 2013. Since this time, laser surgery using the Solomon technique has been used to treat TAPS.
However, despite the research, it is still unknown what the best treatment for TAPS is.
The TAPS Registry
In 2014, the TAPS Registry was established to collate data on the best treatment for TAPS. 370 cases, spread across 17 fetal therapy centers worldwide who collated and collected data on treatments, management, and outcomes for post-laser and spontaneous TAPS cases, were analyzed. Of this, 164 cases were post-laser TAPS, and 249 cases were spontaneous.
The registry was practical and highlighted some important discoveries, like donor twins being at a higher risk of perinatal mortality in post-laser TAPS. It also showed that across all the existing treatment options – expectant management, laser surgery, intrauterine transfusions and exchanges, early delivery, and selective feticide – there was not much difference between these treatment methods concerning the outcome. However, each center recorded different data and sometimes was not followed up – meaning that the information was potentially skewed.
This is why the TAPS Trial was established.
The TAPS Trial
Starting in 2019, the TAPS Trial was established to determine the best treatment for TAPS.
Led by the Leiden University Medical Centre, this randomized clinical trial will place laser treatment against expectant management, intrauterine/partial exchange transfusions, and premature delivery (or a combination of the above).
Parents between 20 and 28 weeks gestation, with stage 2 TAPS or higher, are eligible to participate and will be assigned a treatment protocol through randomization. Participants will be followed up to age 2, with gestational age at delivery, prematurity-related problems, blood work, and procedure-related issues recorded. In addition, long-term development will be assessed at aged 2.
This trial is vital, as without the data it collects, we will potentially remain without the best treatment option for TAPS. This means that many more babies will be born with neurodevelopmental impairment, or deafness, or be at a high risk of dying before birth. With up to 63% of TAPS cases going undetected until birth, it is vital that we can establish the best treatment and save lives.
