October 20, 2005

Fine-tuned freezing improves fertility rate

By Karla Gale

NEW YORK (Reuters Health) - 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

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.