Through her 20s and early 30s, pediatrician Kristie Manning was so neck-deep in medical school and training that she had no time to focus on having children. Still single, the Pleasanton native isn't ready to start a family by herself.
So she bought herself some time. In May, facing the biological threshold of age 35, when a woman's fertility takes a steep dive, she went to the California Pacific Fertility Center in San Francisco and had 14 eggs removed and frozen for future use.
For Manning, those eggs represent an insurance policy of sorts. Even though she's not sure if she will ever use them. Even though there's no guarantee any of the eggs will one day provide a baby. Even though she paid dearly for them.
That $12,000, she says, bought peace of mind.
"I don't know what the future holds, but I feel like I can look back years from now and know no matter what happened, that I did what I could," she said. It also means that if she meets a potential partner, there's less pressure to jump into a relationship just to have kids: "I can think more about if he's the right person."
Manning is among a small but growing number of women in the Bay Area and nationally who have seized on recent advances in "oocyte cryopreservation" to widen the window of time for starting a family.
Over the past decade, clinics that provide reproductive services such as in vitro fertilization have offered egg-freezing to women facing chemotherapy for cancer or other medical issues that could affect their fertility. In the past few years, however, the technology has improved to the point that it's no longer deemed "experimental," and clinics have begun touting it as an option for women who delay starting families in order to pursue advanced degrees, build their careers or meet a suitable partner.
Fertility clinics, including those in the Bay Area, report a rise in egg-freezing procedures in the past few years. The Pacific Fertility Center saw a 277 percent upsurge in cases from 2011 to 2013, while the Reproductive Science Center in San Ramon has seen the number of its cases triple since 2012.
Today, about two-thirds of the nearly 70 fertility clinics in California monitored by the Centers from Disease Control and Prevention market elective egg-freezing for women seeking to extend their fertility.
"Fifty years ago, women would graduate high school or college, go ahead and have kids and be done with childbearing by age 40," said Dr. Phillip Chenette of the Pacific Fertility Center. "Now women's careers are taking off in their 30s, but that's also the time when fertility is declining in a straight line."
About half of all women over 40 have fertility problems, according to the American Society of Reproductive Medicine, and older eggs carry increased risks of chromosomal abnormalities that can cause miscarriage and birth defects. For this reason, women in this age group have much more success using donor eggs when undergoing in vitro fertilization, the Centers for Disease Control reports.
Egg-freezing allows women to preserve their own genetic material for future in vitro fertilization, an option that in some ways gives them more control over their reproductive futures.
"The technology has come so far so far that we think it's like (the introduction of) birth control pills in the 1950s," said Dr. Mary Hinkley of the San Ramon center.
The focus on egg-freezing as a mainstream fertility treatment began after the American Society of Reproductive Medicine in October 2012 removed the "experimental" label and deemed the procedure as safe and effective for producing healthy pregnancies as IVF procedures using live eggs.
The ASRM's move spurred an uptick in women choosing egg-freezing, including at the Stanford Fertility and Reproductive Medicine Center, which works with a gradually increasing number of patients, 50 to 60 patients over the last year, said Dr. Lynn Westphal.
Women who wait until they are 40 to try bearing children must face the likelihood that "probably half their eggs will be chromosomally abnormal," Westphal said. "Any woman in her early 30s who is not sure when she wants to have her children should think about it."
She and other doctors have become more insistent about making this recommendation since the development of a technique called vitrification -- or flash freezing. It has "made all the difference" in preserving women's eggs, Westphal said. In the past, the slow-freezing method caused ice crystals to form that damaged the membranes of delicate egg cells.
"We expect the cryopreserved eggs to remain viable and successful upon thaw, whether they were thawed after one year or 100 years," said Paul Kellogg, a spokesman for the San Ramon center.
However, there's little data on how well frozen eggs hold up, and whether their use will lead to healthy pregnancies, Kellogg and others say.
Chenette cites Italian data when telling women their odds of one day getting pregnant using stored eggs: A woman under 38 has a 30 percent chance of pregnancy during one "transfer" of around six eggs; a woman under 30 has a 50 percent chance.
Still, those odds are good enough for many Bay Area women who want the peace of mind Manning described.
Sarah, 34, who declined to give her full name, is in her first year of a challenging Ph.D. program in psychology. With financial support from her family, she paid $12,000 to undergo the procedure at Stanford's clinic in March.
She's glad she didn't wait. Just as it's harder to get pregnant after 35, the older a woman is the harder it can be for doctors to harvest a sufficient number of healthy eggs. Doctors can retrieve anywhere from six to 25 eggs per cycle. Sarah had seven eggs retrieved, a number her doctor said was sufficient for a successful pregnancy, though Westphal says 12 or more offer a better chance.
"If I had waited two or three years, it would have been more challenging," Sarah said.
Gabriella, who also declined to give her full name, was 27 when she had 18 eggs frozen over the Christmas holidays at the San Ramon center. The Oakland native is still establishing her marketing career in the New York fashion industry and she and her fiancé, 33, don't know when they will be ready to start a family.
She said she and her future husband may not need to use any of her eggs once they decide to have children, but she likes having younger eggs available as a backup.
Because health insurance usually doesn't cover egg-freezing, patients must pay out of pocket for the procedure, which runs anywhere from $7,000 to $12,000. That hefty price tag doesn't cover future procedures for fertilizing eggs and transferring embryos to the uterus.
Egg-freezing also doesn't buy women unlimited time to become a parent. While women's wombs don't age nearly as quickly as their eggs, pregnancy puts a strain on a woman's body at any age. Risks for diabetes and high blood pressure increase in women in their late 40s, Westphal said. Clinics typically won't transfer embryos to women past their early to mid-50s.
As for Manning, she says that while she doesn't know what the future holds, she's grateful the opportunity for potential parenthood was available.
"It's good to know these kind of options exist if things didn't fall into place like you planned."
Age of optimal fertility: 18 to 31
Increase in percentage of women, 35-39, having babies since the 1970s: 150 percent
Number of eggs women have at birth: 1 million
Number of eggs women have at puberty: 300,000
Number of eggs women lose per month at age 40: around 1,000 per month
No. 1 reason women delay childbearing: In a study, 88 percent cited "lack of partner"
Source: Dr. Lynn Westphal, Stanford School of Medicine