Women are faced with two ticking biological clocks: their ability to conceive and the viability of their eggs if they delay having a baby. Many factors can impact fertility, such as the effects of chemotherapy, age and certain medical conditions.

But fertility research in areas such as egg freezing are giving women new choices — and literally changing how they look at their fertility.

“I believe we’ll see a paradigm shift from fertility restoration to fertility preservation in the coming years,” says Richard J. Paulson, M.D., director of USC Fertility, the non-profit fertility practice at USC and professor of obstetrics and gynecology at the Keck School of Medicine of USC. “As egg freezing becomes a recognized option, women will turn to this technology to preserve their fertility for the future.”

Karine Chung, M.D., a physician at USC Fertility and assistant professor of obstetrics and gynecology at the Keck School of Medicine, concurs: “In the last few years, advances in the field have been tremendous. We are seeing success rates for live births from frozen eggs approaching those from frozen embryos.”

The nature of the egg

The biggest challenge is the nature of the egg itself. Unlike an embryo, which has already subdivided into multiple cells, a woman’s egg is a single cell — the largest in the human body — composed primarily of water. As a result, it is structurally unstable and difficult to freeze without ice crystals forming and destroying the cell. “There’s also a problem with the shell,” Paulson points out. “The cooling and defrosting hardens it, making it difficult to fertilize in a petri dish.”

New technology now allows fertility clinics to dehydrate the egg and replace the water with a medical “anti-freeze” that prevents ice crystal formation. Eggs are frozen either with a slow-freeze method or a flash-freezing process known as vitrification. When the woman is ready to be inseminated, the egg is defrosted, reconstituted and fertilized by injecting the sperm directly into the egg.

While all this clinical manipulation may be off-putting to some, Paulson stresses, “The technology doesn’t change the composition of the egg itself.” The results bear him out: babies born from frozen eggs show no increased rate of birth or chromosomal defects.

Even with these successes, Chung cautions that egg freezing is still investigational and that the data are preliminary, based on a limited number of births. She adds that in vitro fertilization (IFV) followed by embryo freezing is still the recommended method for most women. But not all women have partners or — in the case of a woman undergoing cancer treatment — want to choose an anonymous sperm donor under pressure. For these women, Chung says, egg freezing offers the greatest benefit for preserving their fertility.

Extending fertility

“The older the egg, the higher the probability of abnormalities and the greater the difficulty in achieving pregnancy,” says Paulson. While he is not seeing a groundswell, Paulson says, “I’ve started seeing patients banking their eggs as a way to avoid age-related decline in fertility.”

Unlike her eggs, a woman’s uterus is comparatively unaffected by age. So a woman choosing to freeze her eggs when she is younger, saving them for later use, effectively preserves and extends her fertility.

Although egg freezing offers new options for women who delay pregnancy for personal or medical reasons, it raises many questions. For example, at what age should a woman consider egg freezing as a practical investment in future pregnancy?

“Fertility starts showing signs of decline after age 30,” Paulson explains. “A woman crossing that threshold should ask herself if she’s going to have a family by age 35. If not, she should consider egg freezing.”

Paulson stipulates that egg freezing research is ongoing, with many questions still to be answered, particularly on the viability of a woman’s egg that has been frozen for more than five years.

However, he suggests that any woman thinking about preserving her fertility for the future talk to her ob/gyn or a fertility specialist about her options. “The field of fertility is constantly changing and growing. It’s important for women to know what is available to them and what may be on the horizon,” says Paulson.