Dr. De Vita and the miraculous, imperfect mechanics of pregnancy

If the pain Raffaella De Vita had been feeling had been at her knee, she might have been able to name it. As a Ph.D. student and then as an early-career biomedical engineering and mechanics researcher, De Vita had studied the mechanics of injury to tissue like the medial collateral and anterior cruciate ligaments, which connect the shin and thigh bones at the knee.

Instead, the twinge of tugging tissue was coming from the lower sides of her growing bump. 

De Vita was eight months pregnant at the time. In the spring of 2011, each day had her crossing the Drillfield, the central quad of the Virginia Tech campus, to go between her office and her classroom. She’d feel the pulling as she walked the big field’s width. “I remember coming back from class and Googling it,” De Vita said. “What’s going on? Why do I feel this kind of stretch?”

Her searches gave her a general sense of what the pulling could’ve been. “What happens is, the uterus is getting bigger, and there are ligaments attached to it that are holding it in place,” De Vita said. “But as the baby gets bigger and bigger, these ligaments get overstretched. At that point, I remember thinking, ‘I wonder what happens if these ligaments are overstretched to the point that they can get damaged. I wonder if anyone has done anything with these ligaments.’”

De Vita would learn that the stretching of supportive tissue and other natural — and at times, staggering — mechanical changes to a pregnant woman’s reproductive system can result in injuries and disorders that affect millions of women in the U.S. More than 80 percent of women experience some degree of tearing during a first vaginal delivery, and a quarter of all U.S. women are affected by pelvic floor disorders like urinary incontinence and pelvic organ prolapse. 

She would also learn that engineering research on the subject, especially compared to the output of her own field, was sparse. So De Vita began to widen her research focus, first to the ligaments that interested her, and then to the pelvic organs themselves. Now, as head of the  Soft Tissue Research: Experiments, Theory, and Computations by Hokies (STRETCH) Lab, she’s among a small but growing number of researchers studying women’s reproductive biomechanics and their changes during pregnancy, delivery, and the postpartum period.

“If I were not a woman and pregnant, I perhaps would not have developed an interest in studying these ligaments,” De Vita said. “When people talk about diversity in engineering and having different perspectives, that’s what I think about. I think about life experiences that really help us ask different questions and solve problems in a different way.”

‘Can we admit that this is a trauma the body is undergoing?’

During pregnancy, reproductive tissues soften and stretch, remodeling to enable a mother to safely carry and deliver a baby. The uterus expands in volume by about 500 times, according to the Mayo Clinic, and during uterine labor contractions, the system generates up to around 20 kilopascals of pressure to allow for the baby’s passage through the vaginal canal, which also stretches. The cervix remodels to lose nearly all of its mechanical integrity for the same reason. Postpartum, these organs then stiffen and shrink within weeks, days, and even hours of birth.

These kinds of changes enable a feat we should more openly acknowledge and celebrate, said Natalie Karp, a urogynecologist at Carilion Clinic and an assistant professor at the Virginia Tech Carilion School of Medicine.

“We always honor athletes and the amount they put their bodies through to accomplish their goals, but we don’t really honor women and what their bodies go through to accomplish the goal of growing and birthing a human,” Karp said. “That is a big — I feel like the word trauma sounds negative — but it’s a lot for the pelvic floor to go through.”

As responsive as the reproductive system can be to the needs of pregnancy, labor, and delivery, like all systems in the body, it’s imperfect. Injuries happen. Disorders like urinary incontinence and pelvic organ prolapse can arise and persist if they go unaddressed — as they often have, said Karp, who specializes in treating them.

As a urogynecologist, Karp has received training in obstetrics and gynecology, followed by a fellowship in female public medicine and reconstructive surgery. Until her patients are referred to her, though, few of them know Karp’s specialty exists. “I have patients who tell me, ‘I’ve had leakage when I cough or sneeze since I had my baby 30 years ago, and I just thought it was normal,’” Karp said. “We’ll say, ‘it’s common, but not normal.’ It's not something you should feel like you have to live with because that's just what happens when you have kids — which I think is how a lot of women have been treated for a long time.”

De Vita is quicker to go for the word trauma when she thinks about pregnancy as a risk factor for disorders. “I think we need to acknowledge the big impact that having kids has on women’s bodies,” she said. “Can we admit that this is a trauma the body is undergoing? We need to recognize that there can be problems and do what we can as engineers to minimize them.”

‘Together, can we understand the entire reproductive system?’

Lately, De Vita has focused on two subsets of reproductive biomechanics in the context of pregnancy and childbirth: the changes to the uterosacral ligaments that may contribute to pelvic organ prolapse, and the changes to vaginal tissue that may contribute to tears. We still don’t know exactly what happens with these changes from a mechanical point of view, De Vita said.

She sees the first subject as one of a “boat in a dock.” The uterosacral ligaments hold the uterus in place, and during pregnancy, they bear its weight as it grows. The uterus is the boat in the dock, De Vita explained, and the ligaments are the ropes tethering it, keeping it from bumping around. “If the ropes get stretched to the point that they fail, the boat starts to move,” she said.

That kind of loss of support is linked to pelvic organ prolapse, which causes organs to shift and drop. When people experience prolapse, Karp explained, they feel a bulge in the vagina. It’s typically the top or bottom vaginal wall descending, or if the uterus and cervix are coming down, the bulge may be the cervix itself. Prolapse tends to be the most confusing disorder to Karp’s patients.

“That can be really scary, to all of a sudden reach down and feel a bulge,” Karp said.

De Vita’s research group is working to characterize the uterosacral ligaments’ viscoelastic response under a load. Like most tissue, these ligaments are viscoelastic rather than elastic: they lengthen over time when weighed down by something like a growing uterus, and don’t snap back to their original size when the load is removed. As they study how the ligaments deform, the team is looking at their microstructure — collagen, elastin, and other constituent components — to see how that structure might affect the ligaments’ viscoelastic response.

The second of the group’s latest studies examines how vaginal tears propagate, lengthening from the size of a quarter or a grape and splitting into something worse. These tears can create complications like postpartum hemorrhaging, urinary incontinence, and pain during sex. 

“If you have a tear that is this size, and you apply a load, does that tear become bigger?” De Vita asked, holding her thumb and forefinger out and spacing them apart by about an inch and a half. “Given the tear, how does that tear then propagate within the vagina? Because if it propagates, it can tear not only the vaginal wall, but tissues and organs that are connected to it.”

For De Vita, one of the most important questions that still needs answering is how pregnancy and delivery affect not only the individual organs and supportive structures of the pelvic floor, but the whole pelvic system.

She and three of her peers, Kristin Myers of Columbia University, Steven Abramowitch of the University of Pittsburgh, and Kristin Miller of Tulane University, have independently studied the vagina, the cervix, the uterus, and the uterosacral ligaments, but the researchers haven’t yet put their methods and progress together in a single, collective study.

This year, they’ll begin to bring down the silos in their field, De Vita said. In a team project supported by a $2 million grant from the National Science Foundation’s Leading Engineering for America's Prosperity, Health, and Infrastructure program, the researchers will study the interplay of the reproductive organs, each with unique mechanical properties, as those organs cooperatively remodel to make room for a baby, birth that baby, and heal postpartum. 

“If we want to understand the entire pelvic floor, we can’t have different people looking at different components, using different animal models and different mathematical models,” De Vita said. “All of us have an interest in maternal health and the pelvic floor. Everyone has unique and complementary expertise. Together, can we understand the entire reproductive system?”

De Vita ultimately wants to enable women and their health care providers to make decisions backed by quantitative engineering methods that factor in each pregnancy’s unique conditions. Her team’s experiments on deformations and contractions of pelvic organs and tissues feed data into new models, which could add a priori, science-backed thinking to decisions like cesarean versus vaginal delivery, De Vita said.

These models could also guide doctors like Karp in diagnosis and treatment of pelvic floor disorders, including pelvic organ prolapse surgeries. Karp said it’ll be important to look at pelvic floor disorders with an engineering perspective like De Vita’s. “The dedicated biomechanical research that Dr. De Vita and her team are doing has great potential to help pelvic floor surgeons better counsel and treat our patients,” she said.

Nearly a decade has passed since De Vita began asking questions about women’s reproductive biomechanics. Funding agencies have picked up their allocation of grants to maternal health research, which has lived in the shadow of other fields for too long, she said, and it’s been encouraging to see the field grow. Just as exciting to her, though, is the changing conversation. 

Grim realities of maternal mortality persisting in the U.S., compounded by racial disparities in health care, are surfacing in the public eye. Women are sharing more of the unpolished details of pregnancy — donning postpartum undies in photos posted on social media and describing vaginal tearing for followers. 

Photos by Peter Means. Video by Spencer Roberts