Certain high-risk medical devices used in obstetrics and gynecology were approved by the FDA based on flawed data, according to a study from Northwestern University Feinberg School of Medicine.

The team identified and assessed 18 high-risk women’s health devices that were approved by the FDA in the past 15 years, most of them for endometrial ablation that reduces menstrual flow, contraception, and fetal monitoring.

Of the 18 devices, four of them, or 22 percent, were approved even though they failed to demonstrate efficacy in clinical trials, and six of them, or 33 percent, did not have to undergo post-market studies that would survey ongoing safety of the device.

Three devices were actually withdrawn from the market after FDA approval, and according to the announcement, two were not reviewed by experts on the FDA’s obstetrics and gynecology advisory committee. The other device was reviewed but the committee did not recommend it for approval.

“Obstetricians/gynecologists and hospitals who ultimately use these technologies on a daily basis should be cognizant that the clinical studies leading to approval may often be limited,” Dr. Shuai Xu, senior author and a resident in dermatology, told HCB News. “For example, by short length of study, a small number of participants, or not having met predetermined clinical outcomes.”

“Despite this being the most stringent pathway, and despite the fact that we’ve had multiple safety issues connected to OB-GYN devices affecting millions of women worldwide, the evidence leading to approval has a lot of weaknesses,” said Xu.

One of the medical devices that the study authors reviewed was a permanent contraceptive approved in 2002 that is now being evaluated after more than 5,000 women reported pain, organ damage and unintended pregnancy. The authors said that the device was approved based on short-term evidence and insufficient post-market follow-up.

The contraceptive, Essure, is a coil that is placed into a woman’s fallopian tubes and in three months, scar tissue is supposed to form around the device to prevent sperm from reaching eggs. Bayer, which makes and markets the device, will have to follow more than 2,000 women for at least three years, reported CNN, and the study will have to compare women with Essure to women who have had other forms of sterilization.

However, Bayer said that the device is 99 percent effective at permanently preventing pregnancy, according to CNN, and the unintended pregnancies are due to patient error in that perhaps patients did not follow up with their doctors for three-month checkups or did not use birth control in the first three months.

The authors suggest that their results indicate that the FDA’s approvals should be based on more rigorous clinical studies, both before and after the devices are available in the market.

“There are much higher standards for the approval of new drugs, whether oral, injectable or even topical,” said Xu. “The important question to ask is: should we really be holding high-risk medical devices to a lower standard of evidence than drugs?”

They acknowledge that in biomedical research, the randomized controlled trial is oftentimes considered the gold-standard of evidence of safety and effectiveness, and unlike drug trials, it may not be feasible to conduct a randomized controlled trial for medical devices, since it involves both the decision to approve a medical device and then monitoring its safety and effectiveness after approval.

“We should still set a higher bar for approval, including meeting successful primary clinical trial endpoints, ensuring sufficient patient sample size, ensuring sufficient length of patient follow up, and blinding when appropriate,” Walter told HCB News.

The researchers believe their results show that FDA should approve devices based on more rigorous clinical studies than the ones that are currently required, both before and after the devices are available in the market. Lastly, they believe that FDA should seek more input from expert advisory committees and rely on higher quality studies.

“The FDA has a very important, very challenging, and very complex job. The goal ... is not to criticize the FDA, or industry for that matter,” Walter said. “As physicians, protecting the safety of our patients is the most important thing we do.”

“We trust that drugs we prescribe have proven their safety and efficacy in well-designed, rigorous clinical studies that meet the FDA’s appropriately high standards. We believe that medical devices are far behind drugs in this context,” she said.