If you think 50 is too old for a woman to think about having a baby, new research says think again.
A study in Wednesday's Journal of the American Medical Association says healthy women should be able to give birth using donated eggs well into their 50s.
And the study says the chance of becoming pregnant this way is just as good at 55 years of age as it is at 35.
Marilyn Nolen and her husband had been trying to start a family ever since they got married. She went from one fertility treatment to another and by the time she was 50, nothing had worked.
"We tried adoptions and I was told we were too old," she explains.
Finally, at age 54, they tried one last attempt at pregnancy using egg donation: taking an egg from a younger woman, mixing it with her husband's sperm in a lab dish and implanting the resulting embryo in Marilyn's uterus.
Nolen gave birth to twin boys, Ryan and Travis, at age 55.
It has long been known that the older a woman gets, the harder it is for her to conceive. For a woman in her 40s, only one in 10 eggs are expected to develop into a baby.
"It's not that the egg ages at any accelerated rate, but [it is thought] the demands that are placed upon the egg are such that the older egg just cannot sustain it," explains Dr. Richard Paulson, chief of the division of reproductive endocrinology and infertility at the University of Southern California in Los Angeles.
The results of this most recent study of 77 women aged 50 to 63 found that using egg donation resulted in a birth rate of 37 percent. The average age of the donors was 27½ years old.
"Women at 50 can become pregnant with egg donation and they have the same probability of becoming pregnant as younger women," says Paulson, who is the lead author on the study. "The older uterus is able to respond and is able to adapt to the pregnancy and carry it to term."
However, these successful pregnancies do not come risk free for older women. Even among women in their 50s who had passed a rigorous physical, the study found a 20 percent risk of gestational or pregnancy induced diabetes and a 35 percent risk of preeclampsia or pregnancy related high blood pressure.
Cautions Dr. Daniel Lasser, a maternal and fetal medicine specialist at New York Presbyterian Hospital, "This is considered by all doctors to be a potentially life-threatening condition to both the mother and the baby, because it has an effect on a woman's heart, kidney, liver and brain."
According to government statistics, hundreds of women in their fifties are delivering babies each year in the United States. And the numbers are growing.
The American Society of Reproductive Medicine, or ASRM, is one group that worries that egg donation for older women will become a widespread practice too soon.
"The Ethics Committee of the [ASRM] has examined the use of egg donation for post-menopausal women and concluded that the practice, while not unethical in all cases, should be discouraged," says Society president Dr. Sandra Carson in a statement. "The ASRM encourages families to make decisions about having children early in life when medical intervention is less likely to be needed, and if needed, more likely to be successful."
However, others are less concerned that many older women will be signing on for motherhood so late in life.
"One must remember that just because something is possible doesn't mean that it is necessary to do or that everyone will want to do it," says Dr. Mary Lake Polan, professor and chair of the department of gynecology and obstetrics at the Stanford University School of Medicine. "I think there will be few women over the age of 50 who want to conceive and deliver children."
Experts add that those women who find that this option suits them can take heart that their chances at motherhood haven't passed them by simply because they have gotten older.
Adds Paulson, "There is no reason to exclude women over the age of 50 from attempting conception based on age alone."
ABCNEWS' Melinda T. Willis contributed to this report.