Updated 12-6-12: In the video above, Shawn Chavez, PhD, first author of the study, describes the work and its significance.
12-4-12: Couples who turn to in vitro fertilization, or IVF, are desperate to have a family. But, despite many advances, the odds of a successful pregnancy from each round of costly, emotionally demanding embryo transfer are only about 30 percent. The problem stems from the fact that many human embryos are faulty from the earliest stages and will never develop successfully.
Stanford researchers Renee Reijo Pera, PhD, and Barry Behr, PhD, have been working to find out why - and to develop ways to increase the odds of a successful pregnancy through IVF. They report findings from some of their work in today's Nature Communications, which I describe in a release:
The research suggests that fragmentation — a common but not well-understood occurrence in the early stages of human development in which some of the cells in an embryo appear to break down into smaller particles — is often associated with a lethal loss or gain of genetic material in an embryo’s cells. Coupling a dynamic analysis of fragmentation with an analysis of the timing of the major steps of embryonic development can significantly increase the chances of selecting an embryo with the correct number of chromosomes, the researchers found.
"It is amazing to me that 70 to 80 percent of all human embryos have the wrong number of chromosomes,” said [Reijo Pera], professor of obstetrics and gynecology. “But less than 1 percent of all mouse embryos are similarly affected. We’re trying to figure out what causes all these abnormalities.”
Reijo Pera and Behr started a company called Auxogyn to investigate ways to bring these findings into the clinic. The company, which is now privately held, is currently conducting clinical trials of an earlier version of the technique. Reijo Pera and Behr hold stock in the company.
In addition to predicting lethal chromosomal errors, Reijo Pera, Behr and their colleagues are also working to figure out their source. In this study they found that, contrary to previous belief, the father's sperm may also be suspect:
Although the sperm’s role is usually written off as a straightforward delivery of presumably unsullied genetic information, Reijo Pera and her colleagues found that it may not be so simple.
“We learned that about 20 percent of human embryos are normal, about 25 percent are carrying errors introduced by the egg, and the remaining 55 percent have errors that could be caused by either the sperm or the egg,” said Reijo Pera. “And yet, currently, there is almost no screening process: if a sperm is moving vigorously in a laboratory dish, it’s considered to be a suitable candidate for IVF.”