Fine-tuning freezing improves fertility rate

By using sodium-deleted, choline-substituted culture medium and a slow-freeze, rapid-thaw protocol, researchers in Los Angeles have achieved pregnancy success rates of 63 percent resulting from the use of frozen eggs (oocytes).

Dr. John K. Jain and his associates at the Keck School of Medicine of the University of Southern California reported their institution’s outcomes at the annual meeting of the American Society of Reproductive Medicine in Montreal.

In an interview with Reuters Health, Jain explained that oocytes lack a sodium pump, so when they are immersed in traditional culture medium, the presence of sodium is toxic. As for the addition of choline, it acts not only as a constituent of the media but it also ” stabilizes the cell membrane, further enhancing the process,” he said.

So far, the group has frozen and thawed 93 eggs from eight healthy women with tubal factor infertility. Using their culture modifications, 59 oocytes survived and 38 were fertilized. Eight of 29 embryos that were transferred succeeded in implanting, resulting in five pregnancies - a success rate of 62.5 percent on a per-patient basis.

“Implantation rates derived from oocytes cryopreserved by this method are in the same range as fresh or cryopreserved embryos,” Jain said.

“I believe egg freezing has arrived as a technology,” he added, “but I still think it is mandated that we still offer it under research protocols. We need to be advocates for our patients, making sure they know that oocyte preservation is experimental.”

Nevertheless, he noted, their results will be a boon to women with cancer receiving who need chemotherapy or radiation that may leave them infertile or older women who want to preserve their ability to bear children.

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