Pregnancy Scare in the U.K. Implicates Implanon

Jan. 6, 2011— -- The nearly 600 unwanted pregnancies in women using the long-term contraceptive Implanon have called the supposedly high efficacy rates of the device into question, but device-maker Merck & Co. and British health officials hold it's no news flash that contraceptives don't work 100 percent of the time.

The 584 women who have reported the unwanted pregnancies to the Medicines and Healthcare products Regulatory Agency (MHRA) in the U.K. represent less than .04 percent of the over 1.3 millions U.K. users of Implanon since its approval in 1999. Given that clinical trials showed the device to be effective 99.95 percent of the time, these unwanted pregnancies are an unfortunate but not unexpected result.

"There is no contraceptive method that is 100 percent effective and we are very confident in the efficacy and safety of Implanon," said Merck spokesman Ron Rogers.

Dr. Carrie Cwiak, assistant professor of gynecology and obstetrics at the Emory University School of Medicine, echoed that sentiment, noting that "it's important to realize that compared with the 85 percent of women who will get pregnant in any given year with no contraceptive method, or the 15 percent who will become pregnant using condoms, you can see that having less than 1 percent chance with the implant methods, even though it's not zero, is a significant difference."

Some women on Implanon who experienced unplanned pregnancies may not have reported them to the MHRA. But taking the 584 which were reported over the last 12 years, the rate of failure of Implanon "would be more effective than tubal ligation, vasectomy, or any other contraceptive method in history by orders of magnitude," notes Dr. Roger Harms, associate professor of Obstetrics-Gynecology at the Mayo Clinic in Rochester, MN.

In the U.K. 1,607 women have complained about the device over the last 12 years, usually concerning adverse reactions such as pain after insertion, scarring, and other problems. The U.K.'s National Health Services have paid nine women who experienced unwanted pregnancies from Implanon 120,000 pounds (approximately $187,000) in damages and 80,000 pounds (approximately $124,000) in costs, according to the U.K. press.

Implanon is a toothpick-sized implant that contains the synthetic progesterone etonogestrel. When used correctly, it is designed to prevent pregnancy for up to three years. Nearly 500,000 of the devices have been implanted in women in the U.S. since its FDA approval in 2006.

Cwiak says that Implanon and other long-term birth control methods such as the IUD are "very popular" among women looking to avoid pregnancy for a year or longer. The implantation process takes place in a doctor's office with local anesthetic injected into the inside of the arm where the device is implanted.

The MHRA has cited incorrect implantation of the device as a possible explanation for the unwanted pregnancies and Rogers agrees that "the basis for successful use of Implanon is the correct and carefully performed sub-dermal insertion of the implant."