Best of the Awareness Center: Embryo, Heal Thyself

Not much in this world is perfect, but a new medical discovery shows embryos may have a way of perfecting themselves.

The survival of embryo in its earliest stages of development hinges on perfection. Embryos whose cells develop an atypical number of chromosomes have a smaller chance of carrying to term and a greater chance of Down syndrome or another chromosomal abnormality. Some atypical embryos can, however, heal their own genetic abnormalities, according to a new preliminary study conducted by Professor William G. Kearns and his colleagues. The Scientist 

In many in vitro Fertilization (IVF) laboratories, three days after a woman’s eggs are fertilized they are biopsied to see if the five to eight embryonic cells have the correct number of chromosomes. If the cells have too many or too few chromosomes a miscarriage is more likely. The Scientist 

Kearns, an associate gynecology and obstetrics professor at Jon Hopkins Medical Institutions in Baltimore and director of the Shady Grove Center for Preimplantation Genetics, LabCorp in Rockville, decided to see if embryos maintained their genetic defects as they matured between days three and five. His team’s findings backed a theory, originally proposed in the 1990s, but laid to rest in skepticism and an absence of evidence. If proven, Kearns’ theory would have vast implications on IVF and embryo donation and adoption. The Scientist 

Out of the 126 embryos biopsied on day three and used Kearns’ study, 62 were genetically normal and 64 had too many or too few chromosomes. Of the 62 genetically normal embryos 43 (69.4%) developed to the blastocyst stage. Only 25 (39.1%) of the genetically abnormal embryos survived, but 16 (64%) of them appeared normal by day five of development. (European Society of Human Reproduction and Embryology)
Kearns remarked, “These results suggest that there is a dynamic process of genetic normalization that occurs in the developing human embryo.”

Kerns’ theory is that the abnormal cells die or get pushed into the less vital outer shell of cells that will later form the placenta and away from the inner group of cells will develop into the fetus.  He continues, “The exact mechanisms that allow this, however, at this time are still unknown.” ESHRE

While these findings are not 100% conclusive, Joyce Harper, a reproductive geneticist at the University of College London believes that the findings are likely true. She stated, “Kearn’s study just confirms what we’ve said for years. Do not genetically test the embryo on day 3.”

Harper feels that there is nothing to indicate an advantage of testing the chromosomal levels in the embryos prior to the time of implantation. Harper indicated that many presenters have testified that embryos with problems on day three may normalize by day five. The Scientist 

To read more about Kearns’ findings, visit the press site for the ESHRE. Discover responses from embryologists and geneticists at The Scientist.