Noun: an individual (especially an animal) composed of cells of two genetically different types.
[A classic example of expressed mosaicism is the calico cat.]
That’s what one of our embryos is. It came back with some cells having trisomy 19, while other cells were normal.
Trisomy 19 is not one of the more common trisomies. You may know trisomy 21 as Down Syndrome; trisomy 13 and trisomy 18 are also viable but results in babies with severe developmental delays.
This is where the science bumps up against the limit. There are not enough data about what happens when you implant a trisomy 19 embryo – do the irregular cells get outpaced by the regular cells, and you go on to have a healthy kid? Or is the mere presence of a few irregular cells enough to cause problems? Researchers do not yet know.
For the time being, it looks like we won’t attempt to use this embryo.