Should You Consider Using Mosaic Embryos?

straight couple

The term “mosaic” is assigned to an embryo that is found to have both normal and abnormal cells during PGS testing at the 5 day blastocyst stage. In this form of testing, doctors are able to look for and detect, with a high amount of accuracy, the presence or absence of certain genes that may lead to developmental concerns later in pregnancy. For example, tests are often able to detect the presence of an additional copy of chromosome 21, a condition that leads to Downs Syndrome.

In IVF, these tests are generally performed in an effort to transfer only the best quality embryos into an awaiting uterus. With the high costs of IVF treatments and the fact that donor egg cycles often result in more viable embryos than needed, many couples choose to test for abnormalities and then discard any embryos that suggest less-than-optimal chances for implantation.

Despite this common practice, couples are beginning to consider using these “mosaic” embryos. The use of mosaic embryos has been shown to show some promising results for normal pregnancies and healthy children upon birth, which is especially important in cases when the gender of the child is an important factor to the couple,.

A 2016 article published by The New York Times reported 10 healthy births resulting from mosaic embryos. The study also showed a 40% success rate of pregnancy in IVF attempts made with mosaic embryos.

During early cell division, many of the flawed genetic strains that would result in an abnormal pregnancy or birth defect can be lost, or segregated and stored in the placenta. If this were to happen, as opposed to the abnormal cells being stored in the genetic make-up of the fetus, the growing embryo would, in a manner of speaking, be able to “self-correct.”

The alternative would be that the abnormal cells do enter the genetic make-up of the embryo. In these cases, experts suspect that the most likely scenario is that the flawed embryo would fail to implant, or result in a first trimester miscarriage.

It is important to note that the study of mosaic embryos is only in its infancy, and there are no current long-term studies on potential defects that may surface later in life. The prevailing conclusion is that one should be very, very thoughtful when considering the use of mosaic embryos and prepared for any circumstance that may arise as the result of their use. If you have specific questions about mosaic embryos as they relate to your specific needs, you should be sure to speak with your IVF doctor well in advance of your IVF cycle.



Kim Bergman, PhD, a licensed psychologist of 26 years, has specialized in the area of gay and lesbian parenting, parenting by choice and third party assisted reproduction for over two decades. Dr. Bergman has created a comprehensive psychological screening, support and monitoring process for intended parents, surrogates and donors. She is the co-owner of Growing Generations and is a member of the American Society for Reproductive Medicine, the American Psychological Association, the Los Angeles County Psychological Association, the Lesbian and Gay Psychotherapy Association, and the Gay and Lesbian Medical Association. She is on the national Emeritus board of the Family Equality Council. Dr. Bergman writes, teaches and speaks extensively on parenting by choice. Along with co-authors, she published “Gay Men Who Become Fathers via Surrogacy: The Transition to Parenthood” (Journal of GLBT Family Studies, April 2010). Dr. Bergman’s is the author of the book, Your Future Family: The Essential Guide to Assisted Reproduction (Conari Press 2019) as well as the children's book You Began as a Wish (Independent Press 2019). Dr. Bergman created her own family using third party assisted reproduction and she lives with her wife of 35 years. She has two adult daughters.