They cite the medical paradox in which bed rest remains widely used despite no evidence of benefits and, on the contrary, "known harms." They further suggest that in its current form, strict bed rest should either be discontinued or else viewed as a "risky and unproven intervention" requiring rigorous testing through formal clinical trials.

In a paper called "'Therapeutic' Bed Rest in Pregnancy: Unethical and Unsupported by Data" recently published in the journal Obstetrics and Gynecology, Dr. Christina A. McCall and her colleagues make a powerful case against the practice many perceive as cuddly and innocuous.

Bed rest, a growing body of research suggests, may be bad for you. And for physicians to blithely prescribe it is, in a word, "unethical," argue a trio of doctors from the University of North Carolina School of Medicine.

It seems so intuitively right. You're facing the risk of delivering your baby early and the doctor prescribes bed rest. What could be more cozy and safe? Why wouldn't you endure a little extra annoyance (you're pregnant, after all) if it would help keep your tiny, oh-so-vulnerable fetus floating inside the fortress of your womb as long as possible? Even the words "bed" and "rest" feel so inherently soothing and therapeutic.

"If we have anything to learn from the history of medicine it is that instincts and good intentions are a highly fallible compass without the check of scientific controls."

In an email exchange, Dr. McCall clarifies that she is talking about strict bed rest here and adds:

"If a woman feels that increasing her daily rest lessens anxiety or improves symptoms (whatever they may be), then we are not suggesting this should be discontinued. We are merely suggesting that every woman receive INFORMED CONSENT regarding the literature on bed rest and the autonomy to make her own decision."

Research suggests that the potential harms for women on bed rest (a broad term that can include everything from total inactivity to limits on strenuous endeavors like household chores, exercise and sex) can be significant. They range from potentially dangerous blood clots and bone demineralization to muscle and weight loss, financial harship due to restrictions on working and a range of psychological suffering, notably depression.

A report earlier this month, for instance, found high rates of depression and anxiety among hospitalized pregnant women on bed rest and suggested that all women facing this type of confinement undergo mental health screening.

No Benefits

Dr. McCall's conclusions are based on a broad review of the medical literature that found bed rest offers no benefit for the most common conditions it's prescribed for: threatened abortion, hypertension, preeclampsia, pre-term birth, multiple gestations or impaired fetal growth. (Another study published in the same issue of Obstetrics & Gynecology found that activity restriction did not reduce the rate of pre-term birth in women with a short cervix.)

Even beyond these physiological considerations, Dr. McCall asserts that prescribing bed rest is morally questionable and "inconsistent with the ethical principles of autonomy, beneficence, and justice."

Still, the practice remains deeply ingrained. Here are the numbers, according to an accompanying editorial:

As many as 95% of obstetricians report recommending activity restriction or bed rest, in some form, in their practices. Nearly 20% of gravid women in the United States — approximately 800,000 per year — will be placed on bed rest between 20 weeks of gestation and delivery.

Questioning the wisdom of bed rest — which has been used for centuries and viewed mostly as an inconvenient, potentially beneficial and essentially harmless cost of pregnancy — isn't new. For years, data has been mounting on the negative effects of prolonged activity restriction in other medical arenas. Last year the influential American College Of Obstetricians and Gynecologists issued a practice bulletin challenging — but not fully condemning — the practice:

Although bed rest and hydration have been recommended to women with symptoms of preterm labor to prevent preterm delivery, these measures have not been shown to be effective for the prevention of preterm birth and should not be routinely recommended. Furthermore, the potential harm, including venous thromboembolism, bone demineralization, and deconditioning, and the negative effects, such as loss of employment, should not be underestimated.”

What About Maternal Harm?

But Dr. McCall and her colleagues go further, suggesting that bed rest should be limited to formal clinical trials, with written protocols, approval from an institutional review boards and informed consent. As it's currently used, she writes, the practice undermines the spirit of the physician's premier commandment — "do no harm" — in several ways:

"...bed rest conflicts with the ethical principle of justice. Justice requires that clinicians treat individuals fairly and that the provision of care not be discriminatory. Numerous Cochrane reviews regarding pregnancy and childbirth are available, yet the evidence frequently is ignored or interpreted selectively in a way that disregards maternal interests. For example, findings of fetal harm often lead to immediate prohibitions (such as caffeine or various medications), whereas findings of maternal harm or relative fetal safety are overlooked or slowly integrated into practice."

Online Shopping, No Husband

For Kristen Rathjen, pregnant with twins and currently hospitalized and on bed rest at Beth Israel Deaconess Medical Center in Boston, the reasons for staying put are simple: she's already about 2.5 centimeters dilated at 30 weeks pregnant, and she doesn't want to give birth to a premature infant in an ambulance rushing from Mashpee, on Cape Cod, where she lives, into the city.

"I'm just doing what's in the best interest of my child," says Rathjen, a 32-year-old marine biologist. "Sure there's stress, I'm not at home, I don't have my husband or my pets and I've definitely gotten weaker. But the big stress of 'How am I going to get here?' is off my shoulders."

So, for the next few weeks, Rathjen is resigned to forgoing work, accepting boredom and generally following her doctor's advice. "I've got books, my laptop, crafts and really bad TV," she said. "Plus, it's given me time to research baby products and do some online shopping."

Dr. Adam Wolfberg, a maternal-fetal specialist with Boston Maternal-Fetal Medicine, says despite the lack of evidence to support bed rest, there is something real, almost a kind of placebo effect, to women feeling like they are doing something to protect their babies, as opposed to doing nothing.