Embryo Mosaicism: What You Need to Know

In 2005, my associate Levent Keskintepe PhD and I introduced Preimplantation Genetic Screening (PGS) with the ability to identify all chromosomes in the embryo’s cells, into the field of IVF.

This approach, which is now widely used throughout the world, permits selection of those embryos that are most likely to be competent, and has dramatically improved IVF success rates.

However, some abnormal (or aneuploid) embryos are capable of autocorrecting and reverting to a normal karyotype (euploid) during intrauterine development and of then propagating healthy babies. This is because some embryos can harbor both aneuploid AND euploid cells. This combination of aneuploid plus euploid cells in the same embryo is referred to as “mosaicism.”

It is an indisputable fact that many mosaic embryos further cell replication can result in the euploid cell component predominating ultimately resulting in a healthy conceptus. In many cases it is not possible to identify embryo “mosaicism”. Accordingly, we tend to preserve certain aneuploid embryos and recommend that they be transferred.

Once pregnant chorionic villus sampling (CVS) or amniocentesis should be done to determine the normalcy of the pregnancy, providing the patient(s) with the opportunity to terminate such pregnancies if they so choose. Join me tomorrow at 1:00PM PST on my Facebook page, as I address the pros and cons of preserving versus discarding all aneuploid embryos and define my policy in advising such patients.


Connie Gumm

Dr. Sher,

Would you transfer our high level mosaic in a surrogate?

Dup(2)(q31.3-qter)(mos), del(11)(q14.3-qter)(mos)

Dr. Geoffrey Sher

Yes. but only after a full disclosure to the surrogate of all consequences along with her willingness to undergo prenatal genetic testing and elective termination in the event of a defective baby!

Geoff Sher


Ask a question or post a comment

Your email address will not be published. Required fields are marked *