by BARBARA NATTERSON-HOROWITZ
Evolved adaptations of female animals could help solve women’s health challenges
Projected on the massive screen behind me onstage, a herd of giraffes rushes across a sweep of savanna. With the video set to loop, the giraffes gallop endlessly, giving me time to slowly lean across the podium and ask my audience: “Did you spot the pregnant giraffes?” I am delivering a plenary lecture at the 2019 Nobel Conference in Stockholm. The theme of that year’s conference was bioinspired medicine—finding solutions in nature to human health problems—and I wanted to call attention to the connections between women and other female animals.
As a cardiologist and evolutionary biologist, I’d been posing this question about the giraffes to medical students in my courses at Harvard University and the University of California, Los Angeles, for years, so I could tell it had landed as planned. I watched the crowd scan the troop of giraffes for evidence of pregnancy—a baby bump, a lagging mother-to-be. I suspected that few, if any, of the assembled scientists and physicians had considered this question when first taking in the scene. That was precisely my point. Given the importance of female health challenges such as pregnancy to the survival of a species—including our own—shouldn’t the realities of female life in the wild be more than an afterthought for doctors and biomedical researchers?
Predators pose a daily threat to survival for all prey species, and they don’t give pregnant animals a pass. Even in their final, heaviest days of pregnancy, females must evade predators. To do so, they have evolved impressive physiological adaptations.
Consider a giraffe in the last weeks of her nearly 15-month gestation. She has gained hundreds of pounds—her fetus alone weighs up to 150 pounds, but the load is much heavier when you add in the placenta, extra fluid and fat. Yet pregnant giraffes appear to flee as fast as nonpregnant individuals. If they couldn’t, predators would quickly target them as easy prey. That would be the end of the line for that mother, her gestating calf and ultimately the species itself.
As I publicly expressed admiration for the giraffe’s gestational athleticism, I privately cringed a bit recalling how unathletic—how un-giraffe-like—I had felt as a cardiologist in the final weeks of my own pregnancies. I was the slowest doctor in the herd of physicians responding to code blue alerts for medical emergencies at the hospital. I’d become so breathless and exhausted rushing up just two flights of stairs that once, on my way to a cardiac arrest, another physician pulled me aside to express concern for my cardiac health.
I understood why they were worried. Late in pregnancy, women are at risk of developing life-threatening diseases such as preeclampsia and heart failure. Even a healthy pregnancy places significant stress on the heart. The volume of blood that is circulating expands nearly 50 percent. To deal with this increased workload, the cardiac cells and pumping chambers of the heart must grow and transform in size and shape. Cardiologists use the term “remodeling” to describe these changes, but when things go wrong, the consequences are far more serious than a misplaced sofa throwing off the feng shui. Problems with how the heart cells get remodeled during pregnancy are linked to reduced cardiac function and even heart failure soon after delivery.
Fortunately, my cardiac health turned out to be fine: the source of my shortness of breath and fatigue was the nearly 40 pounds of fetus, fluid and fat I’d packed on by the end of the third trimester. Slowing down in the last weeks of pregnancy is perfectly normal for humans—including female cardiologists who can use the elevator instead of sprinting up the stairs.
But in the wild, pregnant animals must maintain their speed and stamina to save their lives. For pregnant gazelles, zebras, and other prey species, the ability to flee swiftly protects them from predation. The animals giving chase are often also female and sometimes also pregnant. To avoid starvation, pregnant cheetahs, hyenas, and other predators need to pursue, overtake and capture fleeing prey. A species in which pregnant females can’t evade predators or capture food is doomed to extinction.
Scientific American for more