Miércoles 12 de Octubre de 2005, Ip nº 130

Ready When You Are
Por Judith Newman

On July 4, a girl born at New York University Hospital by vaginal delivery weighed in at 7 pounds 13 ounces. She looked like a perfectly lovely normal baby, and she is. She is also the future of fertility medicine. The infant, whose parents prefer to remain anonymous, was conceived with an egg that had been frozen and thawed before being fertilized. Only about 125 children in the world have been born from frozen eggs because until this year it was difficult to successfully thaw frozen eggs without destroying them.

But this child is no freak accident. Jamie Grifo, director of the Division of Reproductive Endocrinology at the New York University School of Medicine, and his associate Nicole Noyes have frozen and unfrozen the eggs of eight women. “Five patients had positive pregnancy tests,” Grifo says. “One patient has delivered; two have pregnancies that are ongoing. Those results are comparable to what we see in in vitro fertilization with fresh eggs.”

Each year, one in six couples in the United States—about 5 million people—have trouble conceiving and many seek help from fertility specialists. While freezing sperm and embryos has been standard practice for years, the ability to freeze and then successfully thaw unfertilized eggs has all but eluded specialists. In a sense it’s been the glittering prize of the field because it gives a woman heretofore unimaginable reproductive freedom. If a woman can freeze her eggs when she is young, she can then wait until she is ready to have her own genetic offspring—whether she’s 50, 60, or even older.

There is, of course, an ethical quandary associated with late-life parenthood: If the average life span for women is around 75, should a 60-year-old have a newborn who could be motherless by the time she’s 15? There is also the question of whether young women at their peak of health—in their twenties—will have the forethought and resources to bank their eggs. (Harvesting demands an invasive procedure as well as pricey drugs for ovarian stimulation.) On the other hand, egg freezing could prove to be a marvelous breakthrough for cancer survivors. They can freeze their eggs before treatment and still look forward to having their own genetic children, even if chemotherapy damages their ovaries.

The technology for freezing eggs has been available for years. But eggs contain a large percentage of water, and until very recently that posed a seemingly insurmountable problem. Thawing caused ice crystals to form and prevented meiosis, the cellular process during which an egg’s chromosomes split up from 46 to 23, to be united later with 23 chromosomes from a sperm cell. Only one in 100 frozen eggs were even viable, and a smaller proportion of those resulted in a live human being.

Now scientists seem to have conquered the problem of ice-crystal formation using two approaches. One method developed at McGill University in Montreal, called vitrification, involves freeze-drying: Eggs are plunged into liquid nitrogen and cooled at a rate of 36,000 degrees Fahrenheit per minute to 385°F below zero. When thawed, the eggs have a survival rate of about 90 percent. Another method, developed in the United States and Italy, exploits changes in the chemical composition of the solution the eggs are frozen in. The New York University School of Medicine has a grant to study both methods to see which results in the greatest quantity and quality of viable eggs.

The next child conceived from a frozen egg is due to be delivered in February. Given what this development means to women and their reproductive freedom, perhaps it is fitting that the pioneering baby born at New York University will celebrate her first birthday a few months later—on Independence Day.

  10/02/2005. Discover Magazine.