What Are Mosaic Embryos?

As science continues to advance and doctors learn more about embryos and IVF technology, we continue to see new terminology and practices in the field. Recent studies conducted by the world’s largest genetic laboratory, Reprogenetics, have introduced the IVF community to a new term and potential game changer in the assisted reproductive technologies world: mosaic embryos.

Mosaic is the term now assigned to embryos found to possess both normal and abnormal cells during preimplantation genetic screening (PGS) testing. The testing, typically completed on day 5 of embryo development, is completed by taking a tiny biopsy of the embryo and examining the genetic makeup of the cell. During the examination, embryologists are able to detect, and often diagnose, potential chromosomal abnormalities. These abnormalities, including things like the presence of Downs Syndrome, have traditionally been used to help determine which embryos are chosen as the most likely to implant once transferred. Until very recently, any cell with noted abnormalities was discarded and not considered for transfer.

However, recent developments have led doctors to suspect that these abnormal cells may be viable for transfer after all. Doctors have noted some level of success in transfer of the mixed quality embryos, and many of the births have gone on to produce healthy, normal babies. The belief is that the abnormal cells will be segregated to a part of the pregnancy tissue that is non vital to chromosomal development.

However, if the abnormal cells are not rendered harmless, the embryo will either fail to implant or force early miscarriage as the pregnancy progresses. Clearly, the evidence is far from conclusive and the use of a mosaic embryo could still result in the birth of a child with abnormalities or life altering conditions. As such, the use of mosaic embryos should be very carefully considered with full consideration given to each potential outcome.

Despite the risks, some IVF doctors and their clients are beginning to consider the use of these mosaic embryos; especially in instances where the gender of the fetus is especially important to the parents. In the instance that an IVF cycle results in a small number of a specific gender, and of the small sample there are few solid candidates for transfer, the use of mosaic embryos allows parents to hold out hope for a successful pregnancy in the desired sex.

While research remains inconclusive about the long term impacts of babies born of mosaic embryos, the initial implication could provide additional hope to couples struggling with infertility.

Teo Martinez

Teo Martinez is the CEO of Growing Generations, a surrogacy and egg donation agency headquartered in Los Angeles, CA. Educated at both UCLA and Pepperdine University, and with over 15 years of experience working in assisted reproduction, Teo’s background makes him one of the most experienced and accomplished professionals in the field.