After just a couple of days on bed rest, the material of your body begins to feel different: softer, heavier, a burden to the bone beneath. The thud of the heart in the chest feels deeper: each beat shifts your frame a little. Even though you haven’t used your back for anything, it aches — and when you twist into a new position the ache swivels along with the muscles, can’t be left behind. You fall asleep throughout the day but can’t sleep through the night, and when you bend a limb at the joint, it’s not the transparent sensation you’re used to — you can feel the muscles tugging, the socket creaking in protest. Your body becomes more present, weaker, and more vulnerable: you are aware of it as though it were an alarm that has not yet gone off but could at any moment.

This summer, I checked myself into a progressive Catholic convent in the Pacific Northwest to observe the effects of five days of bed rest on my body and mind. My plan was to spend all but thirty minutes of each day in a small room with framed Bible verses on the walls, lying on my back or side on a spartan twin-size cot. In the thirty minutes I was allowed out of bed, I would shower, take bathroom breaks, or fetch food from the communal kitchen to bring back and eat in bed. In the final moments before my experiment began, I stretched the inner muscles of my thighs and blinked in the warm sunlight. I tried to take pleasure in feeling ordinary, normal, mobile.

Though five days is a relatively short bed-rest regimen, the first week is when some of the most dramatic changes to the body occur. Deconditioning of the cardiovascular system begins within forty-eight hours. The amount of circulating blood decreases, the heart’s total output drops, and the body uses less and less oxygen. Within five days of immobilization, the arteries narrow and stiffen, and the interior lining of the blood vessels becomes less able to flex and tighten.

The body scales itself down rapidly to meet the reduced physiological demands of its new state and then pauses. Eventually, over weeks, bone density decreases and muscle volume declines. Actin and myosin, the proteins that make up muscle, break down into free-floating nitrogen that is flushed from the body through the kidneys. Simply standing up can cause fainting, since the body is no longer used to pumping blood against the pull of gravity.

Hundreds of thousands of years of evolution have enabled us to walk upright, a task few other mammals can manage — sheep and rabbits often lose consciousness or die when held vertical. But the more time a body spends away from plumb, the greater its difficulty in readapting to normal life. For this reason, bed rest is used as an analogue for space travel in NASA experiments: the effect of weightlessness on human bodies can be simulated on Earth by putting subjects to bed at a six-degree negative incline. Prolonged rest is an extreme physiological challenge, a new environment for the body to navigate.

What I’ve described sounds like a sort of bodily erosion, a slow injury or gentle decay, but it also happens to be one of the most commonly prescribed treatments in the United States for pregnant women at risk of preterm birth. Each year as many as 700,000 pregnant women are prescribed some form of bed rest: from several hours a day to round-the-clock immobilization with breaks only to use the bathroom. For some types of high-risk pregnancy, the mother-to-be is hospitalized and prohibited from getting up to relieve or clean herself, from standing, or even from sitting propped up in bed. Strict bed rest — whether at home or in a hospital — often means that a woman has to forfeit exercise, income, and normal domestic tasks such as caring for her family or maintaining her home.

The practice continues despite a growing body of clinical evidence showing that strict bed rest offers no benefits to the fetus or to the mother. It has not been proved effective in treating gestational hypertension, preeclampsia, a shortened cervix, spontaneous abortion, or impaired fetal growth. The hazards of bed rest, on the other hand, are well substantiated: patients may suffer from bone loss, blood clots, muscle atrophy, weight loss, and psychological malaise. Enrollment in one study, in which women carrying twins were randomly admitted to the hospital for bed rest or assigned outpatient care with no activity restriction, was halted midway because of concerns about a possible detrimental effect to the hospitalized group.

Even so, bed rest remains a routine therapeutic intervention for pregnancy, with up to 95 percent of obstetricians reporting that they’ve prescribed it for their patients. Decades after the treatment fell out of favor for other conditions, pregnancy is the last remaining medical territory to which bed rest can lay claim. It is now the domain of those physi cally incapable of movement — those, for example, who have broken all their limbs — and expectant mothers.

When John Hilton published Rest and Pain, his influential 1863 treatise on the beneficial effects of rest, he was writing for an audience that was generally suspicious of the idea of taking to bed. The hospital ward in particular was seen as synonymous with death, in part because of the ease with which infections spread from patient to patient before sanitation standards were adopted.

Hilton sought to change that perception. He argued that nature was the primary agent of healing and that the physician’s best course of action was to let the body rest, so that it might heal itself. The physician could be seen as nature’s assistant, a helpful nurse: “In fact,” wrote Hilton, “nearly all our best considered operations are done for the purpose of making it possible to keep the structures at rest, or freeing Nature from the disturbing cause which was exhausting her powers, or making her repeated attempts at repair unavailing.”

Physicians took Hilton’s recommendations to heart, and rest became the guiding principle of medical interventions, leaving nurses responsible only for the maintenance of good hygiene and the prevention of bedsores. Soon, myocardial infarction, congestive heart failure, tuberculosis, peptic ulcers, and rheumatic fever were all being treated with bed rest. Because rest was an unlimited good, patients were often put to bed at home or in the hospital for indefinite periods of time — the longer the better.

One of the most well respected of these therapies was a “rest cure” that was developed by Silas Weir Mitchell, a physician and author, to treat neurasthenia, a bundle of physical and psychological symptoms that we might diagnose today as depression or anxiety. One monograph on neurasthenia contains a list of eighty-one symptoms, including insomnia, bad dreams, mental irritation, rapid decay of the teeth, dizziness, hopelessness, deficient thirst, vague pains, vertigo, cold hands and feet, and “fear of everything” — a list that the author admits is “not exhaustive.” Women were especially susceptible to neurasthenia, Mitchell wrote, above all “nervous women, who, as a rule, are thin and lack blood.” Their bodies were continually in flux, passing from puberty to pregnancy to menopause, and so were an inherent source of destabilization and pathology.

Women who suffered from nervous pathologies were isolated from friends and family and confined to bed for weeks at a time. In the beginning stages of treatment, patients were forbidden to sit up, sew, read, write, or use their hands for any activity except cleaning the teeth. Each day involved a regimen of “passive exercise,” which consisted of full-body massage and electrical stimulation of the muscles. To counteract the loss of body mass, women were fed a diet that started with a week on an all-milk regimen; patients were conditioned to consume two quarts a day. Over time, they worked up to rich meals comprising mutton chops, cod-liver oil, malt extract, more milk, and doses of a raw-beef soup that was made by dissolving meat with a few drops of hydrochloric acid.

The aim was to produce a more resilient woman by cushioning her systems with blood and fat, and to make her psyche resemble the stillness of her outer flesh at rest rather than the mercurial, reactive processes of the womb. But there was also a punitive dimension to Mitchell’s treatment: he believed that his weak-nerved patients had been coddled by those around them. The neurasthenic woman was “a vampire who sucks the blood of the healthy people about her,” her morality spoiled by undisciplined care and concern. “The moral uses of enforced rest are readily estimated,” Mitchell writes. “From a restless life of irregular hours, and probably endless drugging, from hurtful sympathy and overzealous care, the patient passes to an atmosphere of quiet, to order and control, to the system and care of a thorough nurse, to an absence of drugs, and to simple diet.” Mitchell directed women who had lived selfishly, governed by concern for their own well-being and mental life, to turn their thoughts away from their condition and to focus instead on their duty to others.

This brand of paternalism has mostly disappeared from modern medicine, but its vestiges can be seen in the way we care for pregnant women, whose perceived selfishness (the impulse to continue working or to have a cup of coffee or a glass of wine) is often cast as a threat to their unborn children. When other branches of medicine have abandoned bed rest as a therapeutic tool, why does it linger on in prenatal care? Maybe the answer has to do with the hold that a particular kind of androcentric worldview has over women’s bodies. Though men and women are both made of flesh, women have long been viewed as the fleshier sex, their mental processes unavoidably interwoven with those of their reproductive organs. But even though women were understood to be controlled by their bodies, they were paradoxically capable of obstructing the body’s natural order by exercising autonomy — which could mean deciding not to bear children or threatening gestation through excessive activity and worry. Meanwhile, after doctors observed that wounded veterans returning from the Second World War recovered more completely from their injuries when they spent less time confined to bed, the treatment was essentially abandoned for male patients.

One of the best-known fictional treatments of Mitchell’s rest cure is Charlotte Perkins Gilman’s short story “The Yellow Wallpaper,” about a woman who is confined to bed by her doctor husband and forbidden intellectual stimulation. Gilman was a patient of Mitchell’s, and she spent a month at his clinic. When he sent her home, he instructed her to live “as domestic a life as possible,” lying down after every meal, restricting intellectual activity to a maximum of two hours a day, and heeding his warning to “never touch pen, brush, or pencil as long as you live.” Under Mitchell’s instructions, Gilman’s mental agony only increased, a “mental torment . . . so heavy in its nightmare gloom that it seemed real enough to dodge.” At the end of “The Yellow Wall paper,” Gilman’s protagonist goes insane.

On message boards and in chat rooms, mothers with high-risk pregnancies convene to trade advice regarding bed rest. Women compare the amount of bed rest prescribed (I saw a range from two weeks to twenty-five), ask one another for clarification of their doctors’ orders (are you allowed to sit up?), give practical suggestions (get a minifridge to put by your bed), and discuss ways to pass the time (coloring books, puzzles, Hulu, crocheting, knitting, journaling, posting on Internet message boards). They trade tips on how to reduce back pain, leg cramps, and numbness in the extremities. Messages are supportive and punctuated by smiley faces and small pixelated images of flowers. Below every post on babycenter.com’s Bed Rest Club is a button that allows you to send the writer a virtual hug.

“Does anyone else have days where they just want to cry?” one post asks. “Anyone get put on bed rest and lose all income,” reads another. A strain of guilt and self-recrimination runs through many of the messages: “Being told I had to stop working was really hard, being told I was on bedrest was hard, but being told that my body is failing my baby, that’s the worst. I haven’t even started being a mother and I already feel like a failure.”

For mothers struggling with the effect of bed rest on their families, on their finances, and on their own mental health, adhering strictly to the obstetrician’s orders can serve as an antidote to feelings of powerlessness, a doctor-approved avenue through which the mother’s will can be exercised over her own body. A difficult pregnancy can be transformed into a task that is worked day by day, and online message chains are filled with reminders that the discomfort and stress of being bedridden will all be worth it once the baby has been born healthy. A post titled “Success Story” concludes: “At 24 weeks I was told my cervix was at a 1.1 and had started dilating and funneling. I was put on bed rest with progesterone suppositories . . . I stayed in bed and only got up to pee and shower. I made it to 39 weeks and actually had to be induced. You can do this ladies. My bed rest baby is now 2 years old.”

These testimonials motivate bedridden mothers to keep going, to believe in their own ability to change the course of their pregnancy, and to “keep that baby cooking!” But the logic of the community is self-reinforcing: almost all the women posting on the site are on bed rest or have been in the past, and successful births are retroactively cast as a direct consequence of the time spent in bed. Counterexamples are vanishingly rare, as are community members who’ve ignored a recommendation to go on bed rest — though there are some who have persuaded their doctors to prescribe the treatment after reading in online forums about its success. (Community members likewise talk about successful interventions with the drug terbutaline, which the FDA warned in 2011 “should not be used for prevention or prolonged treatment . . . of preterm labor.”) Failing to follow the guidelines of her physician, or her own sometimes-stricter vision of how much movement she can afford to inflict on her womb, can make a woman with a high-risk pregnancy worry that she has harmed her baby. Contractions or tenderness that follow a day during which she got up or walked more often than she feels she should have are easily perceived as a consequence of her own carelessness or neglect.

Clinical trials are rarely cited on bed-rest message boards, though the moderator of one forum sent me a paper published in 2015 in the American Journal of Health Economics that claimed to show a decrease in very low birth weights and very premature outcomes. It was a statistical analysis of survey responses rather than a controlled trial, and it made no distinction between patients on bed rest for two days and patients on bed rest for weeks or months at a time. I found two small trials, conducted in 1983 and 1992, that suggested there might be some benefit for patients with hypertension. The 1983 trial, however, also noted that a more moderate prescription of four to six hours of rest a day is equally effective in lowering blood pressure.

These studies contrast with the Cochrane reviews of bed rest, which represent the most comprehensive assessment of the available science, and draw from dozens of peer-reviewed papers. Those have consistently shown no proven benefit from the treatment and do not recommend it. A 2013 study of pregnant women with short cervices found that preterm birth was more likely among those placed on activity restriction. Other studies have shown that pregnant women are particularly vulnerable to the negative side effects of bed rest: an increase in clotting factors during pregnancy makes patients more likely to form blood clots, and immobilization compresses the veins further, putting patients at even greater risk. (Pulmonary embolism is the cause of 10 percent of pregnancy-related deaths.)

Obstetricians who have research experience are far less likely to recommend bed rest than those who do not. “Out in the community, you’re going to have doctors that say, ‘Absolutely, you should be on bed rest,’ ” said Cynthia Gyamfi-Bannerman, an associate professor of obstetrics and gynecology at Columbia University Medical Center, where the staff actively discourages the practice. “One of the most common questions I get from my pregnant patients is, ‘When am I going to be on bed rest?’ We tell them, well, hopefully, never. It’s harder, almost, to say, ‘You don’t need it,’ than to say, ‘Okay, sure, go ahead.’ ”

Most of the Cochrane reviews on bed rest were published within the past ten years. Christina Herrera, who is a fellow in maternal–fetal medicine at the University of Utah, said that she learned about the general complications of being confined to bed in medical school but didn’t encounter clinical research about the risks of the practice for pregnancy until her residency. Herrera now tells her patients to avoid strict bed rest at all costs.

One of the greatest obstacles to changing the way bed rest is prescribed is the therapeutic imperative. “Providers feel that they have to do something to help the pregnancy,” Herrera said, “even if there’s nothing they can do. And so women of course jump at the chance to do anything they can . . . if it’ll benefit the baby in any way, shape, or form.” She added: “Historically, women are sacrificial.”

Through some combination of ignorance and wishful thinking, bed rest survives. In 2009, a young woman named Samantha Burton experienced symptoms of preterm labor fifteen weeks before her due date and went voluntarily to Tallahassee Memorial Hospital. She was seen by a doctor who told her that she would have to be admitted and remain in bed. Burton, who had two small children, agreed to rest but wanted to go home. She also wanted a second opinion. The doctor told her that she would not be allowed to leave and initiated legal proceedings to confine her to the hospital. A judge found in favor of Tallahassee Memorial and issued a court order man dating hospital bed rest, medication to prolong her preg nancy, and, if necessary, forced delivery. Three days later, Burton delivered a stillborn baby by caesarean section.

My first night in the convent, I had a quick dinner of scrambled eggs and bagels with the nuns and oblates in the cafeteria. They were kind enough to let me undergo my bed-rest experiment on their grounds, in a wing of the complex meant for spiritual retreatants — all of whom had taken vows of silence for the duration of their stay there, except for me. The nuns were extremely kind and friendly, and unabashedly curious about me, the only visitor to their retreat center who was allowed to talk to them. They asked me about bed rest, why I was doing it, what I thought I would find out. They introduced me to the oldest sister, who had been a nun for more than seventy years. They thought she might be able to tell me about a time when people took to bed more often. (She couldn’t.) They wished me mental and spiritual peace even though they knew that was not what I was there for. Before I left the table, a nun blessed me, blessed my article, and blessed my writing. These were the last people I’d speak to face-to-face for the next five days.

I told the nuns that I expected my time on bed rest to make me better rested, and probably very bored. At that point, I had no idea how draining it would be to adjust my body continuously, as one part after another complained about each new position. I lay on my back or on my side, watching a small rectangle of light blaze and flicker in the afternoon, dimming as the day turned to evening. I breathed deeply even though it felt like my lungs were trapped beneath an invisible new weight. I learned to lie on my side with one leg straight and one bent to avoid the pain of my knee digging into the increasingly tender flesh of the leg beneath. My whole body felt weak and sore and sensitive by day two — but I still felt generally healthy, as though I could shake off this new frailty if I were just allowed to go for a long walk.

By the third day, I found myself thinking that something had gone wrong inside my body, that there was something besides the experiment harming me. What else could explain how unwell I felt? The muscles of my neck and shoulders were alternately sore and numb; my legs hurt when I rested them against each other and ached when they were apart; my heart raced when I turned from one side to the other. I felt sad for no good reason, unfocused but undistractible — I couldn’t seem to get my mind off how I felt, but I was unable to bring the experience into sharp enough relief to analyze it. It’s more difficult to think when you’re horizontal: alertness comes in plains and troughs rather than in peaks. None of my thoughts had any lift to them.

The few times a day when I let myself out of bed, I could feel how different my body had become. Standing up made me dizzy and set my heart pounding. Walking twenty paces to the kitchen exhausted me and left me feeling empty, my legs shaking. I felt as though I’d ended up on the wrong planet, or in the wrong body. I knew from reading NASA’s bed-rest studies that the first week is supposed to be the worst, full of strange pains and headaches, urgent discomforts that last for hours and then fade away. I didn’t know if the second week is easier because the body has adapted, or whether after a week in bed it just gets harder to remember what being out of bed used to feel like, what having a body used to feel like. By the fifth day, I felt as though I’d aged twenty years.

I had read papers that described the dramatic effect of immobilization on the human psyche. Adolescent girls in full-body casts viewed the motion of others with jealousy, tracking them with their eyes, simulating movement with twitches and fidgeting. Individuals forced to rest acted out emotionally, manifesting fear, guilt, and anger. Immobilization altered the perception of weight, pressure, temperature, pattern, and form, and it distorted the experience of time.

The day I left the convent, I wheeled my small, heavy rolling luggage back up the road that led to the bus stop. The distance seemed to have dilated, the inclines and slopes had become steeper. A walk that had taken me ten minutes on the first day now took me closer to thirty.

Lying in bed on my last day of rest, I thought about the phrase “First, do no harm,” which is commonly believed to be part of the Hippocratic oath even though it appeared much later. Intuitively, bed rest feels like it should be a harmless therapy: what danger could there be in doing, for an exaggerated period, something we do every night? If there’s no benefit in it, at least there should be no harm. But in every other branch of medicine, we insist that a treatment justify its use through empirical evidence, through proof of its capacity to help. There’s no excuse for letting any patient suffer the known harm of immobilization without compelling evidence of its benefits. We should recognize bed rest for what it is: not an escape from risk but the adoption of a new risk, one whose outcome is uncertain, but not unknown.