CHICAGO - Ellen Hanrahan, a 36-year-old mother of two, was done having children. To make sure, she had tiny metal coils implanted inside her fallopian tubes, a relatively new form of permanent birth control marketed under the brand name Essure.
A year later, Hanrahan began feeling a familiar form of fatigue - one she'd experienced with her previous pregnancies. Incredu-lous, she took a home pregnancy test. And then another. "I panicked, called my husband and said, 'We have a problem,'" said Hanrahan, who was, indeed, 10 weeks pregnant.
A team of researchers estimated last week as many as 9.6 percent of women could become pregnant within 10 years of undergoing hysteroscopic sterilization, or Essure. That is nearly four times the estimated risk after a laparoscopic tubal ligation, the more traditional method.
The study, published in the journal Contraception, is the first to compare the effectiveness of the two main choices offered to women who seek a permanent form of birth control. About 345,000 American women undergo sterilization procedures each year, with Essure an increasingly popular choice because it does not require a surgical incision.
"Overall, sterilization is very effective; the absolute risk of pregnancy is low," said lead author Aileen Gariepy, an assistant professor in the department of obstetrics, gynecology and reproductive sciences at the Yale School of Medicine. "But if … one method is not as effective, that definitely needs to be part of the decision-making process and not overlooked."
During a laparoscopic tubal ligation, a physician makes a small cut in the abdomen, then blocks, ties or seals the fallopian tubes to keep eggs and sperm apart. Essure also involves blocking the tubes, but instead of using an incision the physician weaves a catheter through the cervix to insert the coils. Scar tissue then gradually forms a barrier.
Essure's manufacturer says clinical trials show the procedure is 99.83 percent effective at preventing pregnancy over a five-year period when used according to approved instructions.
But that rate is for so-called perfect use. Gariepy's team wanted to estimate the effectiveness under real-world conditions, or typical use.
For example, doctors don't always insert the implants correctly, and the fallopian tubes may not become fully blocked. Women are directed to use an alternative form of birth control before returning to the doctor's office after three months to confirm proper placement - a critical follow-up step that some fail to carry out.
For the new study, the researchers used available published data - including reported cases of post-Essure pregnancies - to estimate what would happen to hypothetical groups of 100,000 women using a particular sterilization procedure, including cases where problems occurred.
According to their calculations, 96 of every 1,000 women who undergo hysteroscopic sterilization, or Essure, would get pregnant within 10 years. For laparoscopic tubal ligations, the pregnancy risks were significantly lower: 24 to 30 pregnancies per 1,000 women.
Patients deserve to have this information, which differs from the data provided by the manufacturer, said Dr. Cassing Hammond, an associate professor of obstetrics and gynecology at Northwestern University's Feinberg School of Medicine who was not involved in the study.
But Essure offers advantages that may make it the right choice for some women, he added. "If patients and providers are assiduous during the first year of use, the hysteroscopic Essure implant remains a very effective form of sterilization," he said.
Bayer Healthcare, which purchased Essure manufacturer Conceptus in June, said hundreds of thousands of women have benefited from the procedure since it was approved for sale in 2002. But the company also stresses "no method of contraception is 100 percent effective and pregnancies have occurred in the commercial setting."
The type of mathematical model used by Gariepy's team "is useful in identifying future areas for clinical research," the company said in a statement. Bayer "welcomes ongoing evaluation and research of new innovations in contraception."
Described on the Essure site as "a quick 10-minute procedure that can be performed right in your doctor's office," the technique allows women to return to normal activities within a day or two.
But hysteroscopic sterilization is effective only if both coils are properly placed; estimates of the success rate on the first attempt vary from 76 to 96 percent, according to the Contraception study.
Also, unlike a laparoscopic tubal ligation, which is effective immediately, hysteroscopic sterilization requires several steps, including the three-month waiting period and followup procedure, which is required by the U.S. Food and Drug Administration. Previously published studies on Essure primarily reported the outcomes in women who successfully completed all of the steps, said Gariepy.
"The bottom line is we do see a higher pregnancy risk (with Essure)," she said. "Any time there are multiple steps, there are multiple opportunities for things to go wrong."
Other options for long-term birth control include IUDs and contraceptive implants, which both have a failure rate of less than 1 percent after a year with typical use, according to the Guttmacher Institute. The male sterilization method, vasectomy, also comes in at less than 1 percent.
The institute lists "tubal sterilization" at less than 1 percent, a figure consistent with Gariepy's estimated failure rates for laparoscopic tubal ligations at the one-year mark. By contrast, her team estimated a 5.7 percent failure rate for hysteroscopic sterilization, or Essure, after one year.
According to a recent report on the benefits and risks of sterilization by the American College of Obstetricians and Gynecologists, about 50,000 women underwent Essure procedures between 1997 and 2005, and 64 unintended pregnancies were reported to the manufacturer. Most of these occurred because patients failed to use an alternative contraceptive until it had been confirmed the tubes were blocked, the report said.
But some women say they became pregnant even after completing the follow-up test, which involves injecting a special dye into the uterus and using an X-ray to check whether it leaks past the blockages.
Hanrahan, of Prophetstown, Ill., had Essure inserted in April 2010 and returned in July to confirm the procedure worked. Records provided by Hanrahan state that her tubes were 100 percent blocked, and she was told she could stop taking birth control pills. Her daughter Leena was born in early 2012.
If a woman does become pregnant after Essure, the risks to the mother and the fetus are unknown, according to the Essure.com website.
Distributed by MCT Information Services