The average age of women becoming mothers has risen in the United States, and in the last 20 years, a few women have even entered motherhood in their 60s.
By implanting embryos produced by in-vitro fertilization using egg cells donated by younger women, women who have passed menopause can become pregnant and give birth.
A new study of 101 women age 50 and older who had children using donated eggs reveals that pregnancy at this age carries about the same risks as similarly induced pregnancies in younger women. The study is the largest one to date looking at pregnancy in post-menopausal women.
"These women do really pretty well," said Dr. Mark Sauer, senior author of the article and chief of the division of reproductive endocrinology and infertility at Columbia University Medical Center, where all the women in the study received IVF.
"If they're well-screened and well cared for, they really should do O.K.," Sauer said.
The study found women over age 50 had similar rates of complications, such as gestational diabetes and preterm labor, as women under age 42 who became pregnant after receiving donated eggs.
And although the older women had slightly higher rates of high blood pressure, that difference was small, and may have been due to chance.
The study is published in the February issue of the American Journal of Perinatology.
Pregnancy at older ages
While Sauer said the results of the study were surprising in terms of how well older mothers did, he noted that the women were highly screened and highly motivated.
"These are smart, educated, well-off people that are doing this," he said, and pregnancy after 50 is not common — the 101 cases in the study were collected over a decade.
One 49-year-old woman in the study died while pregnant (she was included in the study because she would have been 50 at the delivery). She had concealed from the doctors that she smoked three packs of cigarettes a day, which the doctors said likely contributed to her heart attack.
In general, carrying a pregnancy is much easier for an older woman's body than producing the egg needed to conceive one.
"The uterus is a very different organ than the ovaries," Sauer said.
Under a microscope, Sauer said, the uterus changes very little with age. Given adequate hormones, an older woman's uteruscan sufficiently nourish a growing fetus.
Eggs, however, are a different story.
A 2009 study from the Sackler School of Medicine in Tel Aviv concluded that age 43 seems to be a cutoff point for IVF with a woman's own eggs, which is viable with only 5 percent of women at that age. While individual cases have been reported of natural pregnancy at older ages, the very fact of their publication suggests how rare such events are.
Sauer said celebrities who have given birth in their late 40s almost certainly used donor eggs, though they may not be acknowledging it. This may be preventing greater public acceptance of egg donation, he said.
In fact, a major challenge in infertility treatment is convincing women in their 40s and older to use donated eggs rather than their own, Sauer said. With donated eggs, the success rate is about 50 percent.
But how old is too old, and who decides?
Public attitudes towards older women having children have changed since research on such cases was first published.
Dr. Richard Paulson, who worked with Sauer in the 1990s on research at the University of Southern California and is currently the director of USC Fertility, said he has noticed a shift in acceptance.
"I think society has become comfortable with [alternative] parent situations," Paulson said.
Sauer believes women should have a choice as to when they have children, but said he understands the concerns.
It was in Sauer and Paulson's research group at USC that a 63-year-old woman became pregnant in 1996. Paulson said she misrepresented herself as 10 years younger.
"We tend to require ID now," Paulson said, noting that many IVF clinics restrict whom they give donated eggs to, with a cut-off age of 50 or 55.
Fifty-year-olds can expect to live another 30 years, and so will be able to raise their children.
"I lose my own personal comfort zone when you get over 60," he said, citing the physical, emotional and financial cost of raising a child, particularly for someone entering retirement.But the doctors agreed that age alone should not be a deciding factor in whether a woman should be treated.
"Of course IVF should not be denied solely based on age," said Dr. Sherman Silber, in Saint Louis, Mo., director of St. Luke's Hospital's Infertility Center.
Paulson said the new study provides more reassurance to doctors offering a reproductive option to older women.
"It points out that it is a relatively complicated pregnancy…but as you can see, most of them get through it just fine," he said.
"But before doing donor-egg IVF on a woman in her late 40s or 50s, you should ascertain that she has a good family support system to take care of the child if she should die before the average age for women in the U.S. of 84," Silber said.