New research is raising fresh concern that an age-old treatment for troubled pregnancies — bed rest — doesn’t seem to prevent premature birth and might even worsen that risk.

Doctors have known for years that there’s no good evidence that bed rest offers any benefit for certain pregnancy complications, and it can cause side effects in the mother, not to mention emotional and financial strain. Yet estimates suggest nearly one in five moms-to-be is told to cut her activity — ranging from quitting work to actually staying in bed all day — at some point during pregnancy.

Now, spurred by the latest study, some specialists are issuing a call for strict studies to finally settle the question — and, until then, for doctors not to assume that a prescription to take it easy can’t hurt.

“Bed rest is misperceived as an inexpensive, innocuous, logical recommendation,” Joseph Biggio Jr. of the University of Alabama at Birmingham wrote in the latest issue of the journal Obstetrics & Gynecology.

In a separate review of past studies that failed to support bed rest, a trio of obstetricians and ethicists at the University of North Carolina at Chapel Hill went further: They said it’s not ethical to prescribe bed rest unless the woman is enrolled in a research study.

A closer look

So why is rest prescribed so often? There aren’t a lot of good treatments to prevent prematurity and other problems.

“Patients want you to do something, and physicians want to do something,” explained Catherine Spong, a maternal-fetal medicine specialist at the National Institutes of Health.

In the latest research, Spong and colleagues took a closer look at a study of treatments for women at risk of premature birth because of a complication called a short cervix. Prescriptions given to women in that study included no sexual activity, partial or complete work restrictions and even complete restriction of non-work activity.

Nearly 40 percent of the 646 women were prescribed some type of activity restriction in the second or third trimester of their pregnancy. Most were told to restrict all three types of activity — sexual, work and non-work.

The surprise: About 37 percent of those who took the recommended precautions had a premature baby, compared with just 17 percent of those who didn’t scale back, the researchers reported.

“The data suggests that bed rest does not prevent preterm birth in this high-risk population, but it doesn’t definitively answer that question,” Spong said. She wants to see a study that randomly assigns women to rest or not.

Stress and anxiety

The new research also raises questions about harm, although the women who rested merely may have been at higher risk for a preemie. They were older and had somewhat more serious cervical complications. But the researchers pointed to other studies that link bed rest to increased stress and anxiety, both of which are associated with prematurity and smaller babies.

In addition, bed rest is well known to increase a mother’s risk of a dangerous blood clot, as well as side effects including loss of bone density and muscle.

The American College of Obstetricians and Gynecologists says bed rest shouldn’t be “routinely recommended” for prevention of preterm birth.

March of Dimes medical adviser Siobhan Dolan said women shouldn’t hesitate to ask their doctors about the pros and cons of restricting activity.

“Sometimes you feel less regret if you did something even though it didn’t change the outcome,” acknowledged Dolan, who said she has prescribed bed rest less often in recent years.

— Associated Press