This article is part of “Innovations In: Kidney Disease,” an editorially independent special report that was produced with financial support from Vertex.
Harriett Oppenheim wasn’t sure she would ever be able to carry a baby. She has lupus, an autoimmune disease, and doctors had told her it would be extremely risky. By the time she got married, the disease had caused so much damage to her kidneys that she had to rely on dialysis. Not only would the kidney damage make conceiving difficult, but pregnancy could be dangerous for her and her fetus.
The kidneys are crucial for a healthy pregnancy: Among other things, they help the body expand its blood volume and regulate blood pressure to support a growing fetus. During pregnancy, the organs kick into overdrive, ramping up blood-filtration capacity by 50 percent or more to remove harmful waste from parent and fetus. Because pregnancy puts so much stress on the organs, people with kidney disease have an increased risk of complications when they become pregnant: preeclampsia (a disorder that can cause dangerously elevated blood pressure), preterm delivery and low-birth-weight babies. The more severe the disease, the greater those risks become. Because of that, in past decades doctors had strongly discouraged women with kidney disease from getting pregnant. And Oppenheim, a lawyer who, at the time, lived in Jackson, Miss., was in the final stage of the illness—kidney failure.
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But in 2014 Oppenheim, then in her early 30s, got married and received a transplant from a living donor. And her nephrologist gave her some surprising news: if she gave the new kidney some time to settle in and all went well, she and her husband could try for a baby. Five years later they became the parents of a healthy boy.
Even for women with advanced kidney disease, having a baby is no longer discouraged. “The research that was driving that decision was pretty small and, honestly, pretty outdated,” says Jessica Tangren, a nephrologist at Massachusetts General Hospital. Today the goal is to make sure that people such as Oppenheim who want to have a baby can do so as safely as possible. There are still risks, but nephrologists who specialize in obstetric care now have better data on them and better tools for managing them. Outcomes have improved as a result. Doctor-patient relationships are also more collaborative. “Over the 20 years that I’ve been doing this, we’ve evolved from a very paternalistic style of practicing medicine, where we’re telling women what to do, into shared decision-making, where we’re discussing the risks and helping patients arrive at decisions together,” says Michelle Hladunewich, a nephrologist and founder of the Kidney Disease and Pregnancy Clinic at Sunnybrook Health Sciences Center in Toronto.
Chronic kidney disease is not uncommon in people of childbearing age. Nearly 8 percent of women between the ages of 20 and 49 in the U.S. have the condition, and the rates are even higher—about 9 to 10 percent—among Black and Hispanic women. In many cases, it’s caused by autoimmune diseases such as lupus or by genetic disorders. In other instances, kidney problems are a consequence of diabetes or high blood pressure.
Doctors have long known that kidney disease increases complication risks during pregnancy, and those risks increase with the severity of the disease. “People who have mild kidney dysfunction really have minimally increased risks in pregnancy compared with people who are at more advanced stages,” says Andrea Oliverio, a nephrologist at University of Michigan Health in Ann Arbor. Quantifying those risks, however, has proved challenging. As Tangren points out, much of the existing data is decades old and no longer relevant.
Data are especially scarce for pregnancy during end-stage renal disease, in part because so few women whose disease has progressed that far have had babies. But that’s changing. Reproductive technologies have allowed women to have children later in life, so nephrologists are seeing more people with poor kidney function who want to get pregnant. “I’m dealing with women who have really quite advanced chronic kidney disease,” Hladunewich says.
Three weeks before Laci Weatherford’s due date, her kidney function dipped and she had to deliver the baby early.
That means a greater risk of complications, chief among them preeclampsia. The condition affects between 3 and 5 percent of all pregnancies. Among people with chronic kidney disease, however, the rates are much higher, from about 21 percent to as much as 79 percent. Untreated, the condition can be life-threatening, causing kidney, liver or brain damage. In rare cases, it can cause seizures or even death. Because the only cure is delivery, labor may need to be induced early.
Researchers don’t fully understand why preeclampsia occurs. It’s possible poor kidney function means the blood volume can’t expand as much as it should during pregnancy, and as a result, the placenta receives less blood than it needs. When that happens, the placenta responds by secreting factors that raise blood pressure in an attempt to draw more blood toward it. “Preeclampsia is basically the placenta crying for help,” says Ananth Karumanchi, a nephrologist at Cedars Sinai in Los Angeles.
Historically preeclampsia has been difficult to diagnose in women with kidney disease. The telltale signs—high blood pressure and protein in the urine—are some of the same symptoms that occur when kidneys start to fail. At times that makes it tricky to distinguish preeclampsia from preexisting problems. But the distinction is important. If preeclampsia is the issue, only delivering the baby can fully resolve it. “In the old days, it was very, very difficult. We would have to biopsy the kidneys sometimes,” Karumanchi says.
Now, however, doctors have a better way to determine preeclampsia risk. In 2023 the U.S. Food and Drug Administration approved a new biomarker test based on Karumanchi’s work that measures the ratio of two placental proteins linked to the development of preeclampsia. Since then, another, similar test has been approved.
These tools have transformed the way doctors manage pregnant women with kidney disease, Hladunewich says. “I don’t guess at the bedside. I now have a whole biomarker system that informs me and helps me make safe choices,” she says. “In the renal population, that has been life-changing.” Pregnant kidney patients with hallmark symptoms of preeclampsia can avoid being prematurely induced if the test shows they have a low risk of the condition. These screens also help doctors catch high-risk women who aren’t showing clear indications of the disorder.
Oppenheim’s pregnancy ran into problems around 35 weeks, when her blood pressure began to rise and her kidney function dropped sharply—signs of preeclampsia. Michelle Owens, a family friend and Oppenheim’s obstetrician, then at the University of Mississippi Medical Center, watched the kidney numbers with concern and decided her best option was to deliver early. The baby boy was born small—four pounds, 11 ounces—but healthy.
Nine months of gestation can challenge even healthy kidneys. People who develop preeclampsia during pregnancy have a greater risk of kidney disease later on, for example, even if their organs were healthy at the start. And those who enter pregnancy with advanced kidney disease often lose additional renal function. Tamara Glavinovic, a nephrologist at the Ottawa Hospital in Ontario, says that’s a frequent concern for people who come in for counseling. “There’s a lot of fear,” she says.
Laci Weatherford, a financial adviser in St. Louis, is intimately familiar with that fear. She was diagnosed with kidney disease after her first child was born and decided not to have more children. “I want to be alive for the kid that I have,” she remembers thinking. But about a decade later Weatherford began to feel queasy in a familiar way. A drugstore test confirmed she was pregnant. “I was embarrassed, I was ashamed. I was so scared,” she says. “I was just really convinced I wasn’t going to make it through.”
As Weatherford’s pregnancy progressed, her kidney function suffered. The decline wasn’t drastic, but it was worrisome enough that her doctors put her on bed rest about seven months in. Three weeks before her due date it dipped even further, and she had to deliver the baby early. The infant, a girl, was born small but healthy.
Weatherford’s kidney disease was in partial remission when her second pregnancy began, and her kidney function bounced back after the birth. For women with more severe disease, however, the loss of kidney function can be dramatic and permanent. Tangren’s research suggests about 7 percent of people with advanced disease lose enough kidney function that they need to start dialysis during pregnancy.
Nephrologists would like to better predict how the kidneys will handle pregnancy based on someone’s individual risk factors, going beyond known danger signs such as protein in the urine and high blood pressure. Most women with chronic kidney disease come into pregnancy with “a constellation of risks,” Hladunewich says. They might be of advanced maternal age or have a high body mass index or diabetes. And it’s not clear how all those individual factors combine to affect overall risks to the kidneys or to the person bearing a child.
Tangren dreams of having “a crystal ball to predict how your kidneys are going to adapt to that hemodynamic stress of pregnancy,” she says—a kind of kidney stress test.
Kate Bramham, a nephrologist at King’s College Hospital in London, and her colleagues are working on such a prediction tool. Their calculator accounts for kidney function, along with other factors such as maternal age, body mass index, blood pressure, the cause of the kidney disease, and the amount of protein in the urine. They hope to forecast whether women are likely to lose a significant amount of kidney function during pregnancy and whether the baby is likely to be born prematurely or small.
Bramham’s research suggests the calculation does a good job of identifying many people who are unlikely to develop complications during pregnancy. “We can confidently use the tool to say, ‘Yes, you’re going to be fine,’” Bramham says. But the tool isn’t as useful for definitively identifying the women who will develop complications: about half of the people the calculator flags as high risk end up having good outcomes. Even though the tool isn’t perfect, Bramham says it can reduce stress for those who end up in the low-risk group.
Improvements in understanding kidney disease and managing dialysis in pregnancy are making it possible for many more kidney patients to become parents. In Europe in the 1980s only 20 to 25 percent of pregnancies in women on dialysis resulted in live infants. But researchers discovered that more intensive dialysis could improve outcomes dramatically. In 2014 Hladunewich and her colleagues published a landmark study showing there was a live-birth rate of 85 percent among women in North America who had received more than 36 hours a week of dialysis while pregnant. Their babies also had much better outcomes. In women who had 20 hours of dialysis or less, the live-birth rate was only 48 percent. Patients who received longer dialysis also had babies at a median of 36 weeks, giving the infants a greater opportunity to thrive. But people who had less dialysis gave birth almost 10 weeks sooner.
And Hladunewich has done other research that suggests the live-birth rate for women who undergo intensive dialysis while pregnant is similar to the rate for women who get pregnant following a kidney transplant—80 and 76 percent, respectively.
But 36-plus hours of dialysis a week is a lot of dialysis. “It’s a full-time job for nine months” or longer, Hladunewich says. “I warn women about that.” Further complicating the problem is that intensive dialysis isn’t always readily available. “Canada has a lot of home-dialysis programs,” Hladunewich says. But there aren’t as many of these programs in other parts of the world, where intensive dialysis “remains a nonstarter,” she says.
When Oppenheim and her husband first asked Owens about having a baby, the obstetrician tried to dissuade them. The risks seemed too great. “This could be really, really dangerous,” Owens remembers saying. But health is only part of the equation when it comes to family planning, and she understands why the couple ignored her advice. “We can tell you what makes the most scientific or medical sense, but we can’t always tell people what’s right for them,” she says. “They knew what they wanted, and they won big.”
Oppenheim’s donated kidney, which she named Kiwi, struggled a bit after her son was born. Oppenheim thinks the stress of delivery triggered a lupus flare, which in turn affected the kidney. But after her illness was under control again, the organ began to recover. Today it’s not as robust as it was before the pregnancy, but it works well enough to sustain her. And Oppenheim’s son is now a bright, energetic six-year-old and an avid reader. His mother has no regrets. “Is he worth it? Totally,” she says.