Mosaic Embryo

Definition - What does Mosaic Embryo mean?

A mosaic embryo is a term used to refer to an embryo that carries both chromosomally normal (euploid) and abnormal (aneuploid) cells as identified during preimplantation genetic screening (PGS) as part of an in vitro fertilization process.

FertilitySmarts explains Mosaic Embryo

Typically during screening, embryos are either classified as normal or abnormal. However, in a very few cases, a unique kind of embryos called mosaic embryos develop after fertilization, possibly due to a mistake in cell division. Because a mosaic embryo contains abnormal cells, there is a risk of miscarriage or abnormal birth. Therefore, some fertility experts do not favor transferring mosaic embryos.

With that said, whether to transfer a mosaic embryo or not a resolved issue, as it might be the only chance for the woman to have a baby. A study carried out by Italian scientists reveals that mosaic embryos can develop into healthy babies. In fact, the scientists report that it's the percentage of chromosomally abnormal cells within the mosaic embryo which predicts the chances of having a healthy or unhealthy baby. The higher the percentage of abnormal cells, the greater is the risk of miscarriage or birth defect and lower is the likelihood of having a successful pregnancy and vice versa.

Moreover, just because an embryo is mosaic during early screening doesn't mean that those cell lines will continue to develop. The abnormal cell line may segregate from the inner cell mass of the embryo, upping the chances of normal birth. Therefore, it is up to the fertility specialist and the intending individual or couple to decide if they'd like to attempt pregnancy with a mosaic embryo or not.

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