Mosaic Embryos May Be Your New Hope To Have A Family Of Your Own.

Mosaic Embryos May Be Your New Hope To Have A Family Of Your Own.

Mosaic Embryos, to transfer or not to transfer? 

Advances in the field of fertility treatment or Assisted Reproductive Technology (ART) has gone through many leaps and bounds. Preimplantation Genetic Screening (PGS) or now better known as Preimplantation Genetic Testing for Aneuploidies (PGT-A) has been used to improve the IVF outcome for couples with infertility.
The test screens through the 23 pairs chromosomes of the embryos and identifies both normal and abnormal chromosomes in the embryos. Embryos that are tested to be normal are those that will be transferred due to its potential to establish into a successful pregnancy.

However, the advances are also stirring debate over so-called mosaic embryos whether they should be implanted. These mosaic embryos are present with normal and abnormal cells at the same time upon preimplantation genetic screening done on a small sample of cells biopsied from the embryos.

Scientifically, these embryos are not regarded as normal, and they should be avoided or set aside. However, what if there are no normal embryos found after PGS but only mosaic embryos?
Should these mosaic embryos be considered for transfer?


For some patients who are struggling with infertility and have limited options, these mosaic embryos may offer new hope or even last hope to materialize their dream of having a family. Especially for those who have failed several times and with biological clock tickling at them, another attempt of IVF cycle may be hard for them.

The doctors at Alpha IVF believe that in some cases, those abnormal cells can self-correct and form into a healthy baby during pregnancy.
In the event where the mother is left with no choice, we may consider transferring single chromosome mosaic blastocysts when there are no normal embryos available or when the likelihood of obtaining an euploid (normal) embryo in a future cycle is bleak. This is done after assessment with a geneticist.

Alpha IVF conducted a study on this practice on 7 patients (mean age: 32.7) who had elective frozen mosaic blastocyst transfer from January to April 2019, with detailed counselling and consent prior to the transfer. The importance of stringent antenatal confirmation of the chromosome status of the fetus was emphasised to each patient.

The Outcome:

Six (6) out of 7 patients became pregnant and gestational sac was confirmed in 4 patients. Two patients were pending for gestational sac scanning at the point of research. One patient miscarried at 5+4 weeks of pregnancy. Antenatal chromosomal testing is being carried out accordingly.

At the point of writing this article, Alpha IVF has recorded 3 healthy live births. These are the living proofs of the value from transferring mosaic embryos.



Based on our preliminary experience, the transfer of mosaic blastocysts can result in good pregnancy rates and should be considered in patients in circumstances stated above. Nevertheless, transferring mosaic embryos is relatively new in the field, hence a proper counselling should be held with the patients and stringent antenatal surveillance for chromosomal status should be emphasised and implemented.

This study was presented at the 9th Congress of Asia Pacific Initiative on Reproduction (ASPIRE), 3-5 May 2019, Central, Hong Kong.
Title :  Clinical outcome following transfer of blastocysts with single chromosome mosaicism
Author :  Lee C.S.S., Low S.Y., Lim Y. X.


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