Looking for a Few Good Eggs

In vitro fertilization eggs may be more easily identified as healthy with new method

(RxWiki News) Ever take home a product and discover it's missing an essential piece? Imagine having to pick the right microscopic package - for one of the most important experiences of your life.

When doctors select eggs to implant in a woman for an in vitro fertilization (IVF) cycle, they can't always tell if the egg has an abnormality that will cause the cycle to be unsuccessful.

A new study has revealed the chromosomal makeup of a human egg, possibly providing a window into individual eggs that would allow scientists to determine if the necessary components for the successful creation of a healthy baby are there.

"Talk to your doctor about any fertility concerns you have."

Pasquale Patrizio, MD, of the Yale Fertility Center, and Dagan Wells at the University of Oxford led a study that identified a couple of genes whose activity may signal when an egg is a "bad egg."

As women age, so do their eggs. And just as humans' bodies slowly break down with age, eggs develop flaws, such as missing or additional chromosomes.

If one of the flawed eggs is implanted during an IVF cycle, the embryo will usually fail. Most doctors implant two or three eggs with the hopes that one will succeed, but then women run a higher risk of having twins or triplets or more. 

Ideally, doctors would like to know which eggs are the "good eggs" before they implant them. That's exactly what this study's findings may one day help researchers do.

Egg cells, called oocytes, are encased in a mass of cumulus cells that help the egg mature. Patrizio and Wells found two genes, called SPSB2 and TP5313, that are in low supply among the cumulus cells around abnormal eggs.

In the cumulus cells surrounding healthy eggs with the right number of chromosomes, however, SPSB2 and TP5313 show up in the right amount.

"We can use cumulus cells surrounding the eggs to gain insight into the health of an egg," said Patrizio. "These cells are now able to inform us about the chromosomal makeup of an egg. This can help us know if it is the 'right egg' to be fertilized and produce a baby."

Even an egg with an inappropriate number of chromosomes can be fertilized and begin growing, but then it has a far higher risk of ending in miscarriage, birth defects, developmental disorders or conditions like Down syndrome.

"This finding opens up the possibility of a safe, effective, and inexpensive way of identifying healthy eggs, potentially lowering the risks of miscarriage and Down syndrome," said Wells.

The study appeared in the May issue of the journal Human Reproduction. The research was funded by Gema Diagnostics, Inc. and the National Institute for Health Research Biomedical Research Center in Oxford. No conflicts of interest were declared.

Review Date: 
June 4, 2012