Kim Myers used to compete in rodeo-style barrel horse races, but after being sterilized with an implantable device called Essure, the pain was so intense that she had to stop.
The device’s small metal and polyester coils had pierced her fallopian tubes, her doctor found, so the two implants were removed. But the sharp, laborlike pains didn’t really subside until three years later, when Ms. Myers had a hysterectomy.
Then her surgeon discovered the cause: A piece of metal coil was still embedded in her uterus.
“Doctors kept saying there was nothing wrong with me,” said Ms. Myers, 53, of Wesson, Miss. “I knew, with every fiber of my being, there was still something there.”
Ms. Myers was among a parade of women who testified before the Food and Drug Administration 14 months ago, saying they’d been injured by Essure and urging officials to pull the device from the market.
Essure comprises two small coils, made of a nickel alloy and a polyesterlike fiber, placed in the fallopian tubes through the vagina. The coils are designed to provoke an inflammatory response that causes scar tissue to form and block the tubes, a process that can take three months.
F.D.A. officials declined to withdraw the device, saying that Essure was safe and effective for many women although some experienced “very serious and sometimes debilitating problems.” But last week the agency ordered that a so-called black box warning be placed on the device’s packaging saying it could cause the kinds of injuries Ms. Myers sustained.
The implant may puncture the fallopian tubes and uterus, and travel into the abdomen and pelvic cavity, the warning notes, causing persistent pain and requiring surgical removal.
Officials at Bayer, which makes and sells Essure, say poor surgical skills are to blame for complications like Ms. Myers’s and insist there is no proof the device causes other reported side effects like chronic pain and autoimmune disorders.
“These are so common to women,” said Dr. Edio Zampaglione, Bayer’s vice president for United States medical affairs.
The F.D.A. also took the unorthodox step of guiding Bayer in the development of a new checklist of risks for doctors to review with patients before implanting the device. The three-page checklist is broken into five sections, each followed by a spot for the patient’s initials, and is to be signed by both doctor and patient.
The checklist is not mandatory, and critics say it does not mention many common side effects linked to Essure, like heavy, painful menstrual bleeding.
Some doctors complain that the checklist is intrusive and burdensome, may dissuade physicians from using the implants, and is based on anecdotes rather than scientific clinical trial data. Some providers, including Planned Parenthood, have said they will inform patients of the risks and benefits, but not ask them to sign the document.
“There’s no question there are complications, but there are risks and benefits to everything we do in medicine, and we don’t have good data to establish the magnitude of the problem,” said Dr. Christopher M. Zahn, the vice president of practice for the American College of Obstetricians and Gynecologists.
“Decisions like these should be made based on data that’s appropriately vetted, not a series of anecdotal reports,” Dr. Zahn said, referring to the black box warning and the checklist.
Dr. Zampaglione of Bayer noted that some studies had shown that other methods of permanent sterilization, not just Essure, have caused serious long-term adverse events as well.
The F.D.A. approved the implant in 2002 after a fast-track review process that prioritized the device because it was the first sterilization procedure for women that could be done in a doctor’s office, without an incision and without general anesthesia. It offered an option to tubal ligation, commonly known as having one’s “tubes tied.”
Pain and other serious side effects emerged in the clinical trials of Essure. The device could not always be implanted, and failed to block the tubes in a significant percentage of patients. According to the new checklist, nearly one in 10 women who try Essure cannot rely on it to prevent pregnancy.
The F.D.A. approved Essure after trials lasting a year or two, even though the implant was meant to last for life. By the end of last year, the agency had received nearly 10,000 reports of injuries and pregnancies related to the device, as well as reports of a very small number of fatalities.
Many doctors who insert the implant do not know how to remove it, the new warnings say. Nor is the best method of removal entirely clear.
The true complication rate also remains uncertain; Bayer would not provide United States sales numbers, which also would not reflect the actual number of women who have received implants, because no one knows how many of the devices have been implanted in the United States.
The original clinical trials did not include control groups for comparison, so it has never been clear whether complications like back pain or heavy bleeding are higher in Essure users compared with women sterilized surgically or who relied on other birth control methods.
By contrast, drug trials are required to have a comparison group of participants who are given a placebo.
Earlier this year, Bayer agreed to begin tracking 1,400 women who have the device implanted over the next five or six years. The study is supposed to report final results in 2023, but is already behind schedule.
This study has a comparison group of sorts: It will also follow 1,400 women who choose a more traditional form of sterilization using laparoscopic surgery.
The women will be followed for three years after the sterilization procedures to see how many in each group develop complications like chronic pelvic pain, heavy bleeding and autoimmune disorders, as well as how often each intervention fails, leading to pregnancy.
Researchers will also track how many women with Essure develop such severe complications that they have to undergo surgery to remove the implants.