After years of struggling with repeated miscarriages and fertility treatments, including in vitro fertilization (IVF), Joanna Brody was thrilled when she finally conceived on her own at the age of 43—even considering the increased risk of health problems associated with pregnancy after age 40. Still, the former marathon runner was in good health and exercised throughout her pregnancy, which was uneventful.

But two days after returning home from the hospital after her daughter’s birth (she also had a 6-month-old adopted son), she woke up feeling like she couldn’t breathe. “I thought I was having a panic attack due to the stress of taking care of two infants while building a new home,” Brody, now 45, recalls.

The next day, when she couldn’t catch her breath walking up a flight of stairs, she rushed to the emergency room. There, doctors discovered that her lungs were filled with fluid, a sign of peripartum cardiomyopathy, a potentially fatal condition that occurs when there’s damage to the heart, resulting in a weakened heart muscle that can’t pump blood efficiently. While it occurs in only about 1 in every 1,300 deliveries, it’s most common in older women, especially those, like Brody, who are over the age of 40.

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The number of women giving birth into their 40s and 50s and beyond is at record highs, according to the Centers for Disease Control and Prevention. In 2007, 105,071 women aged 40-44 gave birth, the highest rate since 1968; the birth rate for women 45 to 54 was 7,349, an increase of 5% in just one year.

“The numbers have really skyrocketed over the last two decades, as research has increasingly shown that older women are able to carry pregnancies and deliver babies safely,” says Mark Sauer, MD, chief of reproductive endocrinology at Columbia University Medical Center and a leading researcher in this field.

Success stories

There’s no official data on how many American women over the age of 54 successfully give birth each year, although there have been plenty of news reports of women in their late 50s and early 60s who have conceived via donor eggs. While older moms have long been the source of biblical legend (think of Sarah, who is said to have given birth to her husband Abraham’s son Isaac at the jaw-dropping age of 90), right now the oldest documented birth mother in the world is Omkari Panwar, a 70-year-old Indian woman who gave birth to 2-pound twins in 2008 via emergency cesarean section.

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But the United States has had its share of 60-plus new moms, too, including Frieda Birnbaum of Saddle River, New Jersey, who in 2007 at age 60 set the record for the oldest woman in the country to give birth to twins. (A 62-year-old, Janise Wulf, gave birth to a singleton in 2006.)

While it may seem nothing short of miraculous that cutting-edge IVF technology is enabling older women to get pregnant, experts are concerned about the increased risk of maternal health problems, ranging from cardiac complications to potentially even a higher risk of developing breast cancer.

“A healthy 42-year-old with no medical problems who is in good physical shape and conceives naturally is likely to have just as nice a pregnancy as a woman who is a decade younger,” says Laura Riley, MD, a maternal-fetal-medicine specialist at Massachusetts General Hospital and chairwoman of the communications committee of the Society of Maternal-Fetal Medicine. “But there are a fair number of women in their mid-40s getting pregnant through IVF who have a ‘touch’ of hypertension, are a little overweight, or are prediabetic, and that’s where we start running into problems.”

Older women are increasingly at risk for potentially deadly complications. A 2002 University of Southern California study, for example, found that 26% of women ages 50 to 54 suffered from preeclampsia (a life-threatening condition characterized by high blood pressure and protein in the urine), and 13% developed gestational diabetes (a temporary form of diabetes that occurs during pregnancy)—and that number soared to 60% and 40%, respectively, for those over the age of 55.

While there are no official guidelines from organizations like the American Society for Reproductive Medicine on how old is too old, leading fertility experts and high-risk obstetricians are voicing concerns about this brave new world of peri- and postmenopausal pregnancy.

“The age cutoff at our clinic is 54, based on the research that shows a marked increase in complications in women older than 55,” says Richard Paulson, MD, director of the Fertility Program at the University of Southern California Keck School of Medicine and one of the country’s leading researchers on pregnancy in the peri- and postmenopausal years.

Others are more conservative. “We have an age cutoff in our practice of 44 years of age for someone using her own eggs and 51 years of age in someone using donor eggs,” says Robert Stillman, MD, medical director of Shady Grove Fertility Center, one of the country’s largest fertility clinics, with 15 offices in the Washington, D.C., area. “We’ve never had a successful birth in a woman over the age of 44 using her own eggs, and we think it’s unethical to promote treatments in a vulnerable population where there’s not a chance of success. We won’t treat women over the age of 51, period, because we believe there are too many risks involved with carrying the pregnancy, both for the mother and for the fetus.”

But many clinics across the United States—including some of the nation’s leading fertility centers—take women who are well into their 50s. So what are these risks, and what exactly do they mean for older wom­en who are contemplating pregnancy? Here, a look at the biggest dangers.