Healthy twins born from uniformly aneuploid embryos

Fully aneuploid embryos transferred during IVF resulted in healthy non-identical twin girls, now nearly seven years old.

Researchers at Stanford University in California have reported that following preimplantation genetic testing for aneuploidy (PGT-A) and thorough genetic counselling, a 42-year-old woman and her 49-year-old partner chose to transfer three uniformly aneuploid embryos – embryos with an abnormal number of chromosomes in every single cell. Subsequently, the woman gave birth to non-identical twin girls, each with a standard set of chromosomes. The girls were born healthy and have continued to develop normally for almost seven years.

'This is a case of a couple who made the informed decision to undergo transfer of multiple aneuploid embryos, ultimately leading to the birth of healthy dizygotic twin girls,' said the authors of the case report, which was published in Fertility and Sterility.

Uniformly aneuploid embryos are not normally transferred due to the very high risk of miscarriage, failure to implant, or a chromosomally abnormal pregnancy. In contrast, there is increasing evidence that many mosaic aneuploid embryos – which have a mix of normal and abnormal cells – can often result in normal pregnancies (see BioNews 1122 and 1312).

This case is unusual because fully aneuploid embryos are rarely transferred, but it shows that self-correction of the number of chromosomes may occur during embryonic development. Furthermore, as the twins are non-identical, they developed from separate embryos, meaning this happened independently in each.

There is no evidence that the embryos were incorrectly designated as aneuploid, but diagnostic errors can sometimes occur, and PGT-A screening techniques have improved in the intervening seven years. Regardless, limited conclusions can be drawn from a single case, as the authors said:

'Larger prospective studies are needed to understand the frequency of euploid live birth after aneuploid embryo transfer and the long-term health outcomes of such children.'

To find out more, the Transfer of Aneuploid and Mosaic Embryo study has been set up, which will explore mechanisms and long-term outcomes in embryos previously considered non-viable.