Sunday, September 14, 2008

Freezing Eggs

Freezing eggs is a concern for those going through IVF and hoping to have good quality blasts to save for another cycle of trying to have a baby. But some women are opting to freeze eggs so that they have a better chance of becoming pregnant later in life. Some are even freezing eggs because of cancer treatments or other serious illnesses that affect the ovaries.

A new process for freezing eggs has improved pregnancy rates with slow freezing or vitrification methods. The process is explained very well at The Infertility Center of St. Louis.

"This new technique of freezing called “vitrification” avoids the damage caused by ice forming inside the cell by not trying to pull every last molecule of water out, because it is impossible to do this 100%. In fact, 70% of the cell is water, and at best you can reduce that to 30%. So with the conventional controlled rate slow-freezing technique, there is always going to be some intra-cellular ice crystal formation, causing some damage to embryos, and severely damaging most eggs. Vitrification uses a super high concentration of antifreeze (DMSO and ethylene glycol), and drops the temperature so rapidly that the water inside the cell never becomes ice. It just instantaneously super-cools into a solid with no ice crystal formation at all.

We can now freeze and thaw, and even refreeze and rethaw, with impunity, using this new protocol from Dr. Masashige Kuwayama from the Kato Clinic in Tokyo. With conventional “slow freezing,” the temperature of the embryo goes down at precisely 0.3°C per minute. With vitrification (using four times the concentration of antifreeze, or cryoprotectant), the temperature is dropped at 23,000 degrees C° per minute, that is 70,000 times faster. At that speed of cooling, and at that concentration of antifreeze, ice crystals simply cannot form."

According to the CBS new article Flash frozen eggs survive more than the vitrified eggs.

"University of Michigan researchers compared the techniques, and found slightly more flash-frozen eggs survived thawing. And it took 21 vitrified eggs to generate a pregnancy, compared with 45 slow-frozen ones. "

Find out which process your clinic uses and ask about their success rates. This might be one of the reasons you choose or not choose to use a certain clinic.

Warning: There is a risk no matter what process is used that some or all of the eggs will not survive the thawing process.

Sources:

The Infertility Center of St. Louis
CBS News article
Extended Fertility
MayoClinic.com

Please post any information you have on the subject.

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