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Mosaic Embryos – What to know about Normal & Abnormal Cells


Imagine this situation: you and your partner have made the huge decision of starting a family together. You both decide to use in vitro fertilization (IVF) and choose a surrogate to deliver your baby. You have invested everything to start your family: time, money, fear, and hope. Unfortunately, this is your one and only shot to get your child, and you and your partner are all in to make your dreams come true. However, reaching for your dreams comes with risks. Your doctor receives a troubling test result: your five-day old embryo has a handful of cells that are abnormal (mosaic embryo) and could lead to developmental defects in your baby. You and your partner are faced with one of the most impossible and unfair questions anyone can be faced with: what do you do?

Mosaic Embryos

This was the harrowing situation that one couple experienced in Kira Peikoff’s New York Times article, “In IVF, Questions About ‘Mosaic’ Embryos”. Roughly 20 percent of embryos have both normal and abnormal cells, which are called “Mosaic” embryos. When fertilized, a mosaic embryo sometimes mistakes in cell division occur and cause abnormal cell lines. If these abnormal cells persists, it can cause miscarriages or, in some rare occasions, serious birth defects. Doctors use a test called Preimplantation Genetic Screening (PGS) to ascertain what cells are normal or abnormal in a developing embryo. The article cites research showing a 40 percent success rate of healthy babies being born from mosaic embryos. These were the tough odds that the couple faced, and in 2014 their healthy baby boy was born.

Despite that couple’s success story, many IVF doctors are hesitant to move forward with the procedure once an embryo is determined to be mosaic. The article cites studies researching mosaic embryos and how accurate PGS tests are in detecting abnormalities. The conclusion from this research is mixed on how well PGS testing can track abnormal cells, and the likelihood that a mosaic embryo will develop into a healthy baby. The sentiment of one doctor quoted in the article sums up the feelings of most IVF doctors dealing with this difficult issue: “A mosaic embryo does have potential for reproduction [. . .] but it could be anywhere on the spectrum from a healthy to a damaged baby, and we don’t know where.” Although more technological advancement and research is needed, one can only hope we hear more success stories like the couple with their healthy and happy baby boy.

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