In a remarkable advance, researchers have shown that older women who have gone through menopause can easily become pregnant using donated eggs.
The breakthrough, published today in the New England Journal of Medicine, gives women who have been considered hopelessly infertile an unexpected second chance, the researchers said.
"It turned their lives around," said Dr. Mark V. Sauer of the University of Southern California, who led the group that conducted the study.
Dr. Sauer and his colleagues at the university reported that five of seven postmenopausal women 40 to 44 years old became pregnant and gave birth to healthy babies.
One of the women gave birth to twins. One of the two remaining women had a stillborn baby and is trying again, the researchers said. The other had a miscarriage.
This is the sort of pregnancy outcome that would normally be expected in younger women with no fertility problems, Dr. Sauer said.
The eggs for the older women were donated by younger women and fertilized with sperm from the older women's husbands in the laboratory, then implanted in their wombs.
"So long as the woman is in good health, there is no reason why she
shouldn't be able to do this," Dr. Sauer said. "There may be 50-year-old women who should be able to do this."
Dr. Marcia Angell, an editor at the New England Journal, wrote in an accompanying editorial, "The limits on childbearing years are now anyone's guess; perhaps they will have more to do with the stamina required for labor and 2 a.m. feedings than with reproductive function."
Dr. Joseph Schulman, director of the Genetics and IVF Institute in Fairfax, Va., and a pioneer in laboratory fertilization, said the upper age limit for pregnancy was "in the 50s, certainly."
Doctors have used donated eggs in recent years to help women in their 30s or younger who had gone through menopause prematurely.
But most researchers had been reluctant to try this fertilization method in older women because they thought that after the age of 40, a woman's uterus was not as capable of sustaining a pregnancy.
Women in their 40s miscarry half of their pregnancies, Dr. Sauer said, while those in their early 30s miscarry 15 percent.
In the new study, the researchers found egg donors through word of mouth and by paying them $1,500. The donors had their ovaries stimulated with hormones to produce as many eggs as possible.
At the same time, the infertile women took hormones to simulate a menstrual cycle that was synchronized with the cycle of the donor.
To the investigators' surprise, they learned that the main reason older women have a harder time having babies is that their eggs are deteriorating, not, as had been assumed, that their uteri are less capable of sustaining a pregnancy.
This means, infertility experts said, that women who are in their early 40s and still ovulating yet who are having great difficulty getting pregnant might do better if they used eggs donated by a younger woman.
"Our feeling is that the biggest interest in these results will not be menopausal women but will be women over 40 who have failed to get pregnant with other technologies," Dr. Sauer said.
He said that without donated eggs, women in their 40s have only about a 5 percent chance of becoming pregnant and maintaining the pregnancy to term, no matter what method of fertility enhancement they use.
"These women have almost a zero percent chance of having a baby," Dr. Sauer said. "They go from a zero percent chance to a chance as good as a younger woman."
A few other doctors, including Dr. Schulman, have quietly begun using donated eggs to help older women become pregnant, with stunning success, but have not always published their results.
Dr. David Meldrum, a clinical professor at the University of California at Los Angeles, said that in his experience women whose only problem was that they had gone through menopause were more likely to become pregnant through the laboratory fertilization method than were younger infertile women who might have had subtle hormonal or physical problems. Dr. Sauer added that there probably is an age at which a woman's uterus is too old to sustain a pregnancy, but until researchers have much more experience with menopausal women having babies, they will not know what that age is.