At least 12 deaths in the last two years have been linked to a popular treatment for obesity, the U.S. Food and Drug Administration warned in a letter to health care providers earlier this week. In most cases, patients died within a month of having a liquid-filled balloon inserted in their stomachs, a procedure that limits the amount a person can eat and helps them feel fuller faster.

Two types of liquid-filled balloon systems have been on the market since 2015: the ReShape Integrated Dual Balloon System and the Orbera Intragastric Balloon System. These balloons are inserted via a minimally invasive endoscopic procedure and are inflated with a saline solution once in place in the stomach.

The balloons are designed to remain in place for several months, while patients receive counseling on diet, exercise, and healthy lifestyle changes. In clinical trials for both devices, patients lost at least twice as much weight with these procedures than with diet and exercise alone.

But in August 2017, the FDA issued a warning about seven deaths that had been linked to the two types of liquid-filled balloons. At the time, the FDA said that it wasn’t clear whether those deaths were caused by the balloon systems, but that it was looking into the possibility.

This week, the agency revealed that five more deaths had been reported since last year’s warning, several of which were linked to perforations of the stomach wall after balloon implantation. In addition to the deaths, other complications related to the placement and use of these devices—such as inflammation of the pancreas, and the balloon filling with air or more liquid and getting too large—have also been reported.

The FDA approved labeling changes last week to reflect this new information and is encouraging doctors to closely monitor patients with intragastric balloons for complications. Health care providers should also talk with their patients about symptoms that could be signs of serious problems, the FDA said, and advise them on what to do if those symptoms occur.

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But the letter does not discourage all use of the Orbera and ReShape balloons. “While these devices remain an appropriate treatment option for some patients with obesity, patients should always discuss with their doctors which treatment option is best for them,” said William Maisel, MD, director of the Office of Device Evaluation in the FDA’s Center for Devices and Radiological Health, in an FDA brief.

Aurora Pryor, MD, director of the Bariatric and Metabolic Weight Loss Center at Stony Brook University in New York, treats patients with both Orbera and ReShape, along with other forms of bariatric surgery. She says doctors and patients should take the FDA’s letter seriously, but that overall, complication rates from these devices remain low.

“Any death in a patient raises red flags and concern, but you also have to consider the large number of people who are using these balloons and look at that proportionately,” says Dr. Pryor. Hundreds of thousands of these balloons have been implanted worldwide, she says, compared to just 12 deaths reported. In statements, Orbera and ReShape manufacturers cited mortality rates of lower than 0.01% and 0.06%, respectively.

“You can’t say that this is a completely safe operation—there are definitely some risks involved. And for a fair consent process, you have to discuss these things with your patients,” says Dr. Pryor. “But I do think if you’re aware of these complications, and you’re looking out for pain and other symptoms, these things can be managed if identified early.”

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Liquid-filled balloons are one of several options for patients considering surgical treatments for obesity. Patients who fit the criteria for traditional weight-loss surgery—usually a body mass index of 40 or higher, or 35 with other health problems—can also opt for a gastric bypass or a sleeve gastrectomy.

Like any surgery, these procedures also come with risks. But they’re generally considered very safe: One 2012 report found that mortality and complication rates for both gastric bypass and sleeve procedures were lower than those generally associated with gallbladder or hip replacement surgery. And according to the American Society for Metabolic and Bariatric Surgery, the mortality rate during the 30 days following bariatric surgery is around 0.13%.

“If people meet the parameters, I will strongly encourage them to have either a sleeve or gastric bypass procedure, as those are the most studied to be effective for weight loss,” says Dr. Pryor. “If somebody has a lower BMI or they don’t qualify for surgery or aren’t interested in surgery, that’s where other options, such as balloons, come in.”

A newer balloon system, called Obalon, is swallowed rather than inserted endoscopically, and is then filled with gas rather than with liquid. At this time, the FDA is not aware of any deaths or serious adverse events related to these newer devices, an agency spokesperson told Health via email. 

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When deciding on any treatment options, Dr. Pryor says, it’s important doctors and patients consider both the risks and the benefits. In the case of intragastric balloons, benefits can include not just weight loss, but also reductions in obesity-related complications like heart disease and diabetes. “Despite the FDA’s warning, I think the balloons are still an excellent procedure,” she says, “and an important option for many patients struggling with their weight.”