February 21, 2008
Fast Freezing Works For Human Eggs?

A San Francisco, California fertility clinic claims it can get excellent rates of viable embryos using eggs frozen with a rapid vitrification technology.

A Pacific Fertility Center (PFC) patient, who underwent an embryo transfer with embryos created from vitrified and warmed donor oocytes (eggs), successfully delivered a baby in late October 2007. A healthy baby boy was born at term. Three other pregnancies are ongoing and are expected to deliver in 2008.

The key is very rapid freezing.

In recent months, the newer vitrification technology has been used at PFC for unfertilized egg preservation. Vitrification works by using higher concentrations of cryoprotectants and much faster cooling rates. Cells are cooled in tiny straws which achieve cooling rates of several thousand degrees per minute. When vitrification straws and cryoprotectants were first approved by the FDA for human embryos, PFC began the process of adapting the technology to unfertilized eggs (oocytes). "Even though we've been handling oocytes and embryos for many years, this technology provided new challenges due to the tiny size of the straws and the speed at which they had to be cooled," says Joe Conaghan, Ph.D., HCLD, Laboratory Director and Embryologist at PFC. "Once proficient with the procedure, we began to freeze high quality oocytes from donors that had proven fertility. Using these quality oocytes, we could be assured that any failure would be the result of the vitrification technology and not the oocytes."

Five oocyte donors in their twenties were recruited and all of their oocytes were vitrified immediately after their oocyte retrieval procedures. The oocytes were then offered to specific PFC patients waiting for embryo donation. The immediate availability of the vitrified oocytes and the ability to choose the sperm source made this a great alternative to accepting donated embryos.

PFC had immediate success with the first recipient. "We had vitrified 16 oocytes from the first donor. For the first recipient we warmed only 7 of these," explains Dr. Conaghan. "Four hours later we injected a single sperm into 6 oocytes that survived the vitrification process (1 oocyte had not come through the process successfully). The next morning, 3 of the oocytes had fertilized. Two days later, 3 embryos were transferred. A positive pregnancy test and ultrasound confirmed a singleton pregnancy. This success was a great reward for our efforts."

Overall, PFC had 7 out of 10 embryos implant after transfers to 6 recipients. What is very exciting is that this implantation rate (70%) is comparable to the implantation rates seen with donor oocytes which have not been cryopreserved.

This technology will expand the market for donor eggs because buyers won't be limited to choices among the cohort of women who are both currently fertile and willing to sell their eggs.

This technology will let women pursue careers for more years before finally trying to have kids.

Share |      Randall Parker, 2008 February 21 10:31 PM  Biotech Reproduction


Comments
Brock said at February 22, 2008 8:15 AM:

This advance is good news too for women who are looking at chemotherapy or some other medical issue which might damage their ovaries. It also levels the play field with men who have been able to freeze their sperm for some time now. A nice advance.

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