High-risk pregnancies are on the rise in the United States and may be more common now than at any other time since modern obstetric care became available.
Why? More fortysomething women are having babies, and epidemics of diabetes, obesity and high blood pressure are causing complications during pregnancy and birth.
But in this otherwise troubling trend is also some good news: A small but growing number of women are having children despite life-threatening conditions that once made a safe pregnancy almost inconceivable.
Exact numbers are not available, but doctors say that tens of thousands of organ transplant recipients, breast cancer survivors, women with heart defects, and even women with the AIDS virus have decided to risk childbearing in the last several years.
Many people worry that some of these women will not live long enough to raise their children, or that they will pass on their medical problems.
Most results have been so surprisingly good that they are overturning decades of gloomy dogma about who is medically fit to have a child.
"These people define a whole new era of pregnancy for us," said Temple University's Dr. Vincent Armenti, who runs a registry that tracks births to transplant patients.
"We have to change our mind-set about the perfect pregnancy," he said. Women should be given advice based on solid research "instead of an emotional feeling that some people just shouldn't have a baby."
No one knows precisely how many high-risk pregnancies there are. It is a catchall term that in the past has meant the woman is over 35 or has a condition like high blood pressure that is dangerous for her or her fetus. But as these situations have become more common, even this loose definition is changing.
Births to women 35 and older are soaring. And many complications are becoming so routine that nurse-midwives can manage them instead of sending women to high-risk care specialists. Doctors say they are treating far more of these risky cases than they did a decade ago.
"Patients are getting older, so by definition, they're higher-risk. The diabetes rate is going through the roof, so that's high-risk. More people with high blood pressure are getting pregnant. The list goes on and on," leaving fewer women considered low-risk, said Dr. Jacques Moritz, director of gynecology at Roosevelt Hospital in New York City.
Dr. Mary D'Alton, the Columbia University Medical Center obstetrics chief, has replaced the term "high-risk" with a 1-to-10 scale.
Birth outcomes for older women and those with medical problems "have been better than we would expect," although complications are more common, she said. For example, about half of organ transplant recipients give birth prematurely, although often by just a couple of weeks.
Dr. Gabrielle Fish felt optimistic when she decided to try pregnancy after her kidney transplant. Fish was in her mid-30s and had been stable on her anti-rejection drugs for two years. After researching pregnancies among transplant patients -- there have been more than 1,000 in the last decade -- she asked her doctors' advice.
"They pretty much encouraged me. They said, 'You're a healthy woman and you don't want to wait till you're high-risk because of your age,' " Fish said.
The result: a healthy daughter, Madelyn, now 6. Fish said she felt lucky to have her but would not try to have a second child.
Carla Taylor, a delivery room nurse from New York, was 42 when she discovered she was pregnant after having artery embolization to treat uterine fibroids. Such women are advised not to try pregnancy because the treatment plugs blood vessels that feed fibroids, and that might keep a fetus from growing properly.
Taylor had a healthy daughter, Bailey, now 6. Moritz, the gynecology director who works with Taylor at Roosevelt Hospital, said 16 of his patients had unexpectedly had children after the fibroid treatment and most had done well.
Doctors expect more of these cases as embolization becomes a popular option to hysterectomy for fibroids, which plague millions of women.
Other reasons high-risk pregnancies are increasing:
* Older moms. In 2005, there were more than 104,000 births in the U.S. to women 40 through 44, and more than 6,500 to women 45 and older. Advanced age raises the risk of birth defects.
* Chronic health problems. Obesity among women 18 to 44 rose from under 9% in 1990 to almost 22% in 2005.
Hospital admissions for diabetes or related conditions among pregnant women and new mothers rose from 175,655 in 1993 to 269,861 in 2004, says the March of Dimes. Admissions for high blood pressure rose from 260,222 to 403,271.
* Multiple births, often the result of infertility treatment. In 2004, they made up about 3% of all live births, up from about 2% in 1980. Such babies are more likely to be born prematurely and to have health problems.
* More cancer survivors. Hundreds of thousands are in their prime childbearing years.