The New Science of the Womb

Over seven months in the fall of 2012 and the spring of 2013, nine women who had been born without wombs received uterine transplants from living donors; mostly, their mothers. The transplants took place in Gothenburg’s Sahlgrenska University Hospital on weekends, when the surgical unit is normally closed. Experts flew to Sweden from the United States, Spain, and Australia. Ten gynecologists and surgeons, as well as support staff, worked on their off-hours, hoping to be part of medical history. A private research foundation covered their costs. Two months after the transplants, the women began menstruating. Five years after the first transplant, eight children had been born to that initial cohort.

In the years since, the pioneering surgeons have refined the technique: It is now possible to remove a uterus from a deceased donor, revivifying it as soon as it is sutured to the recipient’s blood vessels. The surgeons perform the removal with a robotic arm, operated with joysticks observed through a large screen, a video game of epic and minute proportions. One bioethicist has said that, as the science advances, “it may be legally and ethically impermissible” not to consider offering this procedure to trans women, ostensibly a step toward reproductive equality for all.

Yet anyone paying attention to the news has probably grasped that societies all over the world are drifting further away from a vision of reproductive equality. In China, Hungary, North and South Korea, Poland, and the United States, among other places, politicians lament the decline in the number of children being born and implore—or coerce, subtly or overtly—people to have more. They hold out carrots (monthly stipends, housing loans, baby bonuses) in an effort to rev wombs up. They craft legislation giving them ostensible dominion over wombs, attempting to dictate what can and cannot happen within them. But as enthusiastic as they are about controlling wombs, they, and quite frankly the rest of us, know shockingly little about these organs from whence we all sprung.

A new crop of books unpacks the history of uterine misunderstanding, medical mysteries, and misogyny to teach us more about this extraordinary organ. These books trace the womb’s evolutionary origins, enlighten us about its myriad functions and dysfunctions, and envision a potentially transcendent future, in the midst of an all-too-dystopian present.

Anyone who has had a difficult pregnancy or witnessed one up close may wonder why we can’t simply lay eggs, like our distant avian relatives. Indeed, as Cat Bohannon observes in Eve: How the Female Body Drove 200 Million Years of Human Evolution, the “majority of multicellular animals lay a clutch of eggs.” The placenta had evolved sometime before the apocalyptic event known as Chicxulub, when an asteroid or comet hit the earth some 66 million years ago. But it was around the time of the impact that incubating eggs inside the body really took off. This party trick came with evolutionary advantages: Gestating creatures could search further afield for food without worrying about an untended nest, while providing a more stable and controlled bacterial environment and temperature.

Of course, there were downsides, too. Internal gestation didn’t just reshape our reproductive organs, but pulled in the immune system and the metabolic system, too. As we became placental mammals, Bohannon writes, “the entire female body became a gestation engine.” Of course, humans still do produce eggs, through the process known as folliculogenesis. After leaving the ovaries, in humans, they travel to the fallopian tubes. If they are fertilized, they then attach to the endometrium, or the uterine lining, and the two entities—uterus and embryo—work together to grow the placenta. A squirrel-like creature, Protungulatum donnae, whom Bohannon calls “Donna,” may be the first creature to have a modern placenta as well as a single fused womb (smaller mammals such as mice still have two uteri and two cervixes and produce litters). This ancient uterus evolved from “a muscular, oozy organ that secreted all the stuff necessary to produce an eggshell,” Bohannon writes; it marked the moment evolution turned “the mother’s body into a combination of eggshell and nest.”

Besides her primitive uterus, Donna, who lived 67 million to 63 million years ago, had another useful evolutionary alteration—her legs didn’t splay out to the side, but ran more perpendicular to the ground, hinting at what would eventually become the upright, bowl-shaped pelvis that supports an occupied and growing uterus. Birthing live young also led to another extraordinary evolutionary step. Instead of a cloaca, the single cavity through which egg-laying mammals such as the platypus also excrete urine and feces, our ancestors went on to develop a three-holed female pelvic plan, with a vagina, urethra, and rectum. Clearly, the babies that emerged into the world sans a coating of fecal matter and its dangerous intestinal bacteria had an evolutionary advantage. (Human embryos still develop a cloaca at five weeks, which then divides into the urogenital and rectal passages by the sixth and seventh weeks; the full suite of orifices is complete by about week 20.) But even with this clever bit of engineering, as placental mammals evolved to become larger, and to gestate longer, birth became riskier. By the time Homo sapiens evolved, our highly invasive placentas put us at risk for internal bleeding. And the large size of human skulls relative to the size of the pelvic opening (a mismatch that gave rise to the memorable image of “shitting a pumpkin”) means that some sort of miracle had to occur for humans to reproduce so successfully. That miracle, Bohannon says, was midwifery.

Scientists have observed small groups of female bonobos, a female-dominated primate society, guarding a birthing mother. In several cases, they “even cupped their paws under the newborn as it came out of the mother,” instances of “bonobo midwifery.” But bonobos, chimps, and other primates have relatively straightforward births. Human birth is far more complicated: Our labors are long and involved, sometimes beginning dangerously early, sometimes well overdue. So humans, with their innate sociality and emergent tool use, invented what Bohannon calls “gynecology,” defined by her as the “continually evolving body of medical knowledge and practices” to prevent, manage, or otherwise intervene in female reproduction. This includes using herbs as abortifacients, creating gynecological tools to prevent infections or stanch uterine bleeding, or eating certain plants to enhance fertility (something that primates have also been observed doing) or guide labor. Every known human society has records of gynecology. Without this innovation, without learning to care for the wombs among us, our species, with its terribly designed reproductive system, might have died out long ago.

Gynecology also couldn’t have developed without a cooperative female society, Bohannon observes—a culture that encouraged women to support one another in their most vulnerable moments (“Trust Women,” as the slogan goes). Yet for much of its recent history, this field that is centered around the bodies and lives of women and their babies has been dominated by men who frequently held women in varying degrees of contempt. A surprising share of the extant gynecological record is a history of misogyny and misunderstanding on the part of male physicians. While some of this misunderstanding is only fair, given the scientific tools available, some of it is deeply intertwined with sexism. Aristotle’s influential theory of reproduction posited that semen provides “the form and the efficient cause” of a new being, while the female provides “the material” (menstrual blood, he hypothesized) that gets added as the embryo grows, supplying the reproductive foundation for the long-standing binary of superior male activity versus inferior female passivity—the egg waiting to be fertilized; the vacant, inert womb waiting for something to do. His theory dominated until the seventeenth century; it wasn’t until the discovery of the human ovum in 1827 that our understanding of reproduction gained a firmer grasp on the female role.

Despite this limited understanding, innovations in gynecology continued in fits and starts, with most occurring in the last 200 years. In Womb: The Inside Story of Where We All Began, the writer and midwife Leah Hazard relates the first account of an unsuccessful hysterectomy in 120 CE, when Soranus of Ephesus removed a gangrenous prolapsed uterus via the vagina, but lost the patient. An early account of a successful (self-administered!) hysterectomy came in England in 1670, when “an attempt to carry ‘a heavy coale’” left a local woman with a prolapsed uterus (when the uterus drops into the vagina), which she addressed by cutting it out herself, severing her bladder and part of her vagina as well. A male midwife arrived and stitched her up, although the stitches didn’t hold, and she suffered lifelong incontinence. In the mid–nineteenth century, the notorious “father of modern gynecology” J. Marion Sims, working in Alabama, developed techniques such as fistula repair and tools such as the speculum, by experimenting on enslaved women and their babies with little regard for their suffering or humanity. Hazard quotes his own admission: “If there was anything I hated, it was investigating the organs of the female pelvis.” Despite his “undisguised distaste for women’s bodies,” he seemed to enjoy the renown they brought him, often performing his surgeries “in front of a small crowd of other admiring physicians.”

The mid-1800s, a period Hazard calls the “infancy” of obstetrics, was also a moment in which traditional midwives fell out of fashion. “Having a man at the foot of one’s bed—potentially with a shiny new invention like forceps in his hand—became a sign of status and sophistication available only to the very wealthiest society doyennes,” Hazard writes. As generations of female knowledge fell into the shadows, prominent men came to dominate the field. In a typical example, John Braxton Hicks, a London physician working in the second half of the century, identified the uterine contractions that can occur at any point during pregnancy and don’t signal the onset of labor. Naturally, he gave them his name, even though, Hazard writes, “one suspects that this characteristic of the womb had already been experienced and acknowledged by generations of women since time immemorial.”

To be fair, there could be advantages to having one of these men with shiny instruments attending your birth, since it was largely men who were able to study the latest surgical techniques and important developments, such as the use of antiseptics to prevent dangerous bacteria from developing in wounds. Murdoch Cameron, a chief obstetrician at Glasgow Maternity Hospital, was one of these men. He is considered to have performed the first modern antiseptic cesarean sections (C-sections) in 1888. Since antiquity, people had extracted babies by slicing open the abdomen (the name, Hazard suggests, more likely refers to Julius Caesar’s decree to use this method of extraction if the mother’s life was threatened, rather than to his own abdominal delivery), but until Cameron’s intervention, “infection and blood loss made the procedure so dangerous that it was used only as a last resort.” Cameron had studied at the Glasgow Royal Infirmary under the pioneering surgeon Joseph Lister, and he was confident that “Lister’s tried-and-tested carbolic acid solution” had its place in obstetrics, not just general surgery. In contrast to many other instances of obstetric breakthroughs, we know the name of the woman on whose body science took its strides. Patient A was Catherine Colquhoun, a woman barely four feet tall, whose pelvis was “severely narrowed by the rickets that plagued so many of the city’s slum-dwellers.” In fact, her pelvis was just an inch and a half in diameter, making vaginal delivery assuredly fatal to mother and child alike. Catherine had a safe abdominal delivery and recovered under the care of many nurses, leaving the hospital just over a month after she’d been admitted, with her son, Caesar Cameron Colquhoun, in her arms.

Throughout this period, the nonpregnant womb was imagined as a sterile, empty space, “a kind of crystal ball—unblemished and pristine,” Hazard writes. This image was reinforced by the invention of early human incubators, an idea borrowed from the chick hatcheries of the Paris Zoo by the French physician Stéphane Tarnier. He asked the zookeeper, Odile Martin, to construct a “couveuse sufficiently ventilated and large enough to hold one or two infants,” which looked something like a large, glass-topped toaster oven, according to an 1897 account with illustrations in The Lancet. These were a notable improvement on the swaddling and warming that human cultures had always done for their young; with constant attendance, they could be kept at a stable temperature, and allowed the infant to breathe. In Eve: The Disobedient Future of Birth, author Claire Horn notes that while “Tarnier’s incubators would likely have held infants not less than thirty-eight weeks old,” the physician nevertheless boasted “that he was on the cusp of enabling almost the entire latter half of gestation to occur through his technology.” He had an eager audience for his claims: Infant mortality was high, and premature births were (and remain) common. But the audience was wider than those in the medical profession. A pair of doctors (one a pediatrician, one, it transpired, a self-proclaimed doctor) took incubators to exhibition halls, beginning with the Kinderbrutenstalt (child hatchery) at the 1896 Great Industrial Exposition in Berlin. The self-proclaimed physician, Martin Couney, later set up “a permanent ‘incubator baby show’ at Coney Island’s Luna amusement park in 1903.” Although Couney was uncredentialed and operated without oversight, Horn writes, “his patients received a level of care that would have been unavailable anywhere else at the time.” They were fed by wet nurses and monitored around the clock “by healthcare professionals who practised meticulous hygiene.” Tarnier may have profoundly overestimated his own ingenuity, but his devices and their descendants have helped save countless premature infants’ lives.

More than a century later, we are on the cusp of accomplishing Tarnier’s dream of realizing the back half of a 40-week pregnancy outside of the human body. But just as we plan for life on other planets while proving ourselves embarrassingly incapable of caring for our own, the advances in artificial womb technology belie a discomfiting degree of ignorance about the wombs inside of us. It was only in 1979 that an Israeli scientist, Vaclav Insler, examined the uteri of 25 women who’d agreed to be inseminated with a stranger’s sperm just before scheduled hysterectomies, discovering the cervix’s active role in filtering and housing sperm in “over 20,000 tiny ‘crypts.’” The cervix gatekeeps access to the womb, such that “the percentage of colonized crypts and sperm density were severely reduced in patients inseminated with abnormal sperm,” Insler wrote, although Hazard notes that it’s unclear whether sperm fitness or cervical selectivity is behind this. Far from being a passive crystal ball, the unpregnant uterus is hard at work.

Doing what else, exactly? Part of the reason we know so little is that, like almost everything else with respect to women’s health, research in this area has been underfunded for most of medical history. For example, Hazard searches the medical literature and finds 15,000+ search results for sperm or semen, compared with 400 for menstrual effluent (the mixture of blood, “endometrial cells, mucus, native bacteria … and vaginal secretions” that we think of as our periods). But the tides are finally shifting, and scientists and doctors around the world are engaged in fascinating new explorations of the womb and its functions and dysfunctions. Dr. Christine Metz, head of the Laboratory of Medicinal Biochemistry at the Feinstein Institutes for Medical Research, and an ob-gyn researcher at North Shore University Hospital, had to overcome the “yuck factor” to get other physicians to help her recruit patients whose menstrual effluent she could study. She hopes to analyze this matter to identify cells that would indicate the presence of endometriosis, which would provide a noninvasive way to screen for a painful disease that can take seven to 10 years to be diagnosed and involves uncomfortable biopsies in which tissue is scraped from the lining of the womb. Still, in a telling sign of who controls the purse strings and how widely they are missing the point, one of the comments she received in applying for a National Institutes of Health grant was, “That’s ridiculous, why collect menstrual effluent when you could just collect biopsies on these women?”

Remarkable discoveries await those who care enough to look closely at the womb, and Hazard’s book takes us on a tour of this knowledge frontier. For example, in the past two decades or so, study of the uterine microbiome has overturned the “sterile womb” paradigm that reigned for over a century. As scientific advances made it possible to identify microorganisms and bacteria through the detection of genetic debris, scientists analyzing meconium, the fecal matter produced by newly born infants, showed it to be full of bacteria, and not just in babies born to women known to have infections, suggesting that the fetus’s first home is a lively, teeming bacterial ecosystem. Dr. Frances Byrne, a researcher at the University of New South Wales, is investigating what the uterus can tell us about the relationship between endometrial cancer and obesity. Obese women, she has found, have microbiome signatures that are similar to women, obese or not, who have endometrial cancer. And women with cancer had lower levels of the “good” probiotic bacterium lactobacillus, relative to the controls. Dr. Margherita Turco is generating a placental “organoid,” a reconstituted model of the placental tissue made from endometrial and early placental cells, that allows her to study how the placenta grows and what it secretes—things that, in Turco’s words, “we still don’t know anything about.” These little endometrial organoids have the potential to lead not just to a better understanding of the dialogue between the endometrium and the placenta it helps grow, but to the creation of bespoke IVF regimes tailored to each patient’s window of implantation and hormonal response.

With existing technologies, such as medication abortion, we are also gaining more control over our wombs. In the United States today, self-managed abortion, usually done with pills, now accounts for the majority of abortions. Knowledge is more accessible, thanks to the internet. People with underdiagnosed conditions such as endometriosis and polycystic ovary syndrome, or PCOS, find community and resources online. Young people openly discuss their periods on social media, and menstruation has become a larger part of the global health and gender equality conversation. Even the academy is taking menstruation seriously: In 2020, an academic publisher released The Palgrave Handbook of Critical Menstruation Studies.

In spite of these advances, so much uterine knowledge remains buried. Among the frustratingly basic questions we still do not have answers to: Why do contractions start when they do, and why do women go into preterm labor? Why does the composition of menstrual effluent vary so widely among women, from 1 to 2 percent blood to 82 percent blood in others? Why are so many uterine events that could potentially be catastrophic for our species—miscarriage, an embryo’s failure to implant, stillbirth, preeclampsia—still so poorly understood? What is a “hostile uterus” and an “incompetent cervix,” and why can’t we have more precise and less insulting names for those nebulous conditions? What is the actual connection between the womb and mental health, not just the one that Bohannon notes was believed by “otherwise intelligent Europeans” until a little over a century ago, that “the uterus drove women to huge, disruptive emotional outbursts”?

As some researchers begin to answer those elemental questions, others are engaged in a multisited arms race to develop an artificial womb (also sometimes called partial ectogestation, or artificial amnion and placenta technology). In 2017, researchers at the Children’s Hospital of Philadelphia published a breakthrough paper, “An extra-uterine system to physiologically support the extreme premature lamb,” which detailed how their “Biobag” kept lambs at the human gestational equivalent of 23 to 24 weeks alive in a womblike, sealed environment filled with lab-made amniotic fluid; the fluid-filled design, critically, allows the lamb’s lungs to follow a more normal path of development, as they would in utero, compared with current practice of being in an incubator and receiving oxygen via a ventilator. In September 2023, the FDA met to discuss how potential human trials of this technology might be carried out.

Similar projects are underway in Australia, Japan, and the Netherlands. All have as their stated aim to help premature infants born before 28 weeks, some, perhaps, as early as 22 to 24 weeks. Indeed, the impetus for the device came from Children’s Hospital of Philadelphia research fellow Emily Partridge, M.D., Ph.D., who, according to a university press release, “experienced the challenges of caring for critically premature infants.” This is undoubtedly noble and necessary work. Preterm birth is the number one cause of infant mortality worldwide; about 15 million babies are born preterm each year. But that is not necessarily how the devices will be used. One only has to look as far as the reproductive priorities of one of the richest men in the world to see how this might go awry. In January 2022, when Elon Musk tweeted about population collapse, several tech bros jumped in to propose synthetic wombs as a solution. “We should be investing in technology that makes having kids much faster/easier/cheaper/more accessible … Synthetic wombs, etc,” replied one investor and entrepreneur. Another, inadvertently channeling Shulamith Firestone, proposed, “Synthetic wombs would remove the high burden of pregnancy, significantly reducing the inequality” between women and men in their careers.

Those wombs are almost here. So what should we be thinking about as they creep toward reality? Horn, an academic who works at the intersection of law, policy, and reproduction, asks first-order questions about access to such a technology. Would this brand-new, cutting-edge, and presumably expensive solution be available in the nations where the greatest number of preterm births occur, such as India, China, Nigeria, Pakistan, and Indonesia, and where electricity is not always reliable? Or among the communities within rich countries whose maternal and fetal health is most at risk?

Horn also dwells on the idea, floated by bioethicists for decades now, that artificial wombs will provide “the abortion solution,” a way to end a pregnancy while maintaining the life of the fetus. But such a glib, “win-win” take on ectogenesis ignores many obvious questions that arise if one pauses for even a moment to think about the reality of this possibility. If the pregnant person doesn’t want to be a parent—presumably why they are seeking to end the pregnancy in the first place—who will care for the surviving fetus? Is it truly permissible to require someone to submit to what will presumably be an invasive medical procedure to extract a fetus rather than take a few pills that can end the pregnancy? Does proposing artificial wombs as an abortion solution require, fundamentally, viewing women and people with wombs as incubators that can easily be swapped for a mechanical version? When I think about what could go potentially awry, one possible nightmare is someone like Elon Musk buying as many artificial wombs as he can afford (thank goodness he lost so many billions buying Twitter) and manufacturing a little army of children with his sperm in an effort to counter what he perceives as population decline, an idea not too far afield from what Jeffrey Epstein was planning, only Epstein proposed using actual women to gestate his babies at a Santa Fe, New Mexico, ranch. If there’s one thread that runs through these worst-case scenarios, it is a lack of respect for wombs and the people who live with them—usually, but not always, women. Horn’s conclusion, that artificial womb technology arriving in a racist, misogynistic, classist, and eugenicist world stands a high likelihood of being used toward racist, misogynistic, classist, and eugenicist ends, is hard to dispute.

And yet the prospect of uterine transplants for trans women, alongside other horizon technologies such as in vitro gametogenesis, or growing eggs and sperm from stem cells, may offer interesting liberatory possibilities. Not just in chipping away at one of the most obvious markers of biological sex difference—after all, it still takes male and female gametes to reproduce—but in the very quest to understand what makes a uterus work, and how it might function in someone assigned male at birth. The nuance and depth of understanding of the human reproductive and endocrine systems required to pull off such a feat would have benefits for everyone, womb or not.

But Horn maintains, and I agree, that asking the womb to be the site of reproductive liberation perhaps asks of it too much. After all, we can achieve much of what the artificial womb purports to solve with simpler, low-cost interventions: Better nutrition and access to quality prenatal care, for example, would go a long way toward improving outcomes in places like India, where short maternal stature and congenital and neonatal infections have been linked to or identified as causes of preterm birth. Cleaner air could help prevent nearly a million stillbirths per year. Social, economic, and environmental conditions, not a lack of artificial wombs, are behind the reluctance of many people to have children—as feminist author Lyz Lenz tweeted back to the tech bros, “Men would rather develop robot wombs than advocate for paid leave.”

In other words, we could get a lot closer to reproductive equality with some very basic measures—addressing medical racism, having adequate nutrition and healthy air and water for everyone, and even just learning more about the basics of the human body, especially the long understudied female body (womb included), which could enlighten us about the health of all bodies. Horn proposes a vision of reproductive equality that emphasizes a broader equality, less narrowly focused on reproduction: “a future in which the weight of carrying a pregnancy is shared, not through automating gestation, but through the provision of resources, support and care.” A future, in other words, that recalls our distant past, when our ancestors understood that knowledge, care, and respect for the womb—and its bearers—held the key to our species’ implausible success.