With improvements in egg-freezing technology over the past few years, it's likely that more and more women will opt to have the procedure as a way to ease the stress of a ticking biological clock, experts say.

But for the procedure to work best, women would need to freeze their eggs in their 20s or early 30s — many years before they may be thinking about starting a family. Moreover, egg freezing still does not guarantee a pregnancy, experts say.

Egg freezing has been around for decades — mainly used by women who needed chemotherapy for cancer or other conditions and who were facing slim chances of having healthy eggs after their procedures — but older techniques were less successful because the freezing process caused crystals to form in the egg cell, which damaged the structure of the cell. As a result, eggs were often not viable after they thawed.

But a new technique, called vitrification, has come around in the last five years or so, and freezes the eggs so quickly that the damaging crystals don't form. In 2012, the American Society for Reproductive Medicine (ASRM) said egg freezing should no longer be considered experimental because eggs frozen with vitrification are similar to fresh eggs in terms of their ability to lead to pregnancy, at least in cases where eggs are frozen from women at a young age. [Future of Fertility Treatment: 7 Ways Baby-Making Could Change].

Since that announcement, fertility specialists say they've seen much more interest in egg freezing. Dr. Tomer Singer, director of the Egg Freezing Program at the North Shore Long Island Jewish Health System, estimates that before 2012, his clinic saw about five to 10 patients interested in egg freezing per year. Now, he gets the same number of inquiries on a weekly basis.

And interest could rise further as the technique is perfected and the cost comes down, Singer said. Currently, the cost of egg collection can range from about $5,000 to more than $15,000, depending on where women have the procedure done and how many eggs they freeze. (That does not include the cost of required medications, which are thousands of dollars more.)

Ticking biological clock

Egg freezing is viewed as a way to thwart women's "ticking clock," which stems from the fact that as they grow older, it becomes more likely that their eggs contain chromosomal abnormalities, increasing the risk of miscarriage and certain disorders. For example, a woman's risk of conceiving a child with Down syndrome increases from about 1 in 350 at age 35, to 1 in 100 at age 40, to 1 in 30 at age 45, according to the Mayo Clinic.

At the same time, more and more women are putting off having children to pursue their education or career. Over the last four decades, the rate of women who gave birth to their first child between ages 35 and 39 increased more than sixfold — from 1.7 first births per 1,000 women in 1973 to 11 births per 1,000 women in 2012, according to a report released last month by the Centers for Disease Control and Prevention.

If a woman needs to use in vitro fertilization (IVF) to become pregnant later in life, she has a greater chance of success if she uses younger eggs (either eggs of her own that she froze at a young age, or eggs from a donor). In this way, egg freezing provides women the opportunity to preserve their fertility while pursuing career goals or looking for Mr. Right, experts say.

"The power in egg banking is that it allows women to have the freedom to keep looking for the right partner, and alleviates that stress that occurs when a woman is in her late 30s and early 40s and hasn’t quite found the right person," said Dr. Wendy Vitek, a fertility expert at the University of Rochester Medical Center. In addition, freezing eggs earlier in life does not lower a woman's chances of getting pregnant naturally later, Vitek said.

Most women who come to Vitek's clinic are in their late 30s or early 40s — ages at which their chances of becoming pregnant with their own eggs are reduced, she said. Ideally, women should freeze their eggs in their 20s or early 30s, but this requires a lot of forward thinking, and may also not be affordable for young women, Vitek said.

Still, as awareness of the procedure spreads, more young women may opt for egg freezing, Vitek said.

Not a guarantee

But some experts are cautious about saying how much women's lives could really change in the future as a result of egg freezing.

For instance, cost is one factor limiting the procedure's availability. "I don't know when it will become something that every woman could do," said Dr. Beth Kennard, director of the Division of Reproductive Endocrinology and Infertility at the Ohio State University Wexner Medical Center. "The first in vitro fertilization [procedure] was in 1978, and in vitro fertilization is still not something every woman can afford to do," Kennard said. In 2010, about 1.5 percent of U.S. births were through assisted reproductive technology, which includes IVF, according to the CDC.

In addition, the procedure does not guarantee pregnancy. According to the 2012 ASRM report, which looked at studies conducted in Europe on frozen (vitrified) eggs from donors under age 30, pregnancy rates ranged from 36 to 61 percent. And according to an online fertility calculator, which is based on information from a study published in 2013, a woman who freezes 15 eggs at age 32 has about a 28 percent chance of becoming pregnant by using them. (The calculator is based on work from researchers at New York Medical College and the University of California Davis.)

"It's not a guarantee that you're going to be able to have children when you come back and thaw them out," Kennard said. (Natural pregnancy rates are not 100 percent either; among couples without fertility problems, 60 percent will become pregnant within three months of trying.)

Still, the age of the egg is generally the biggest factor affecting pregnancy rates for women who choose IVF, Vitek said. The pregnancy success rate of women who use IVF after age 42 is 4 percent for one cycle, according to a study that included mostly women who used their own eggs.

For women who freeze their eggs at a young age, "if they do find the right person in their mid-40s, it [may] not be too late to have a biologically related child," Vitek said.

And not all women who bank their eggs would need to use them — they may find the right partner and conceive naturally without requiring assisted reproduction, Vitek said.

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