The combined analysis included nine studies comparing different implantable contraceptives. More than four out of five women who participated in the studies had the implants for two years or longer, suggesting that they were satisfied with the birth control method.
The most common side effect with the implants was irregular menstrual bleeding, with cessation of periods increasing with duration of use.
"Menstrual disturbances are common, and these side effects should be explained to women before the implant is inserted so that women can make an informed choice about their contraceptive strategy," says researcher Jo Power of London's Margaret Pyke contraceptive center.
Implantable Contraceptives in the U.S
Implantable contraception has had a rocky history in the U.S and was not even an option for women in this country for several years before 2006.
Exactly one year ago, the FDA approved Implanon, a matchstick-sized implant that delivers a steady dose of the hormone progestin to prevent pregnancy for up to three years.
Implanon is inserted by a doctor under the skin of the upper arm, and it can be removed at any time.
The single-rod delivery system for Implanon is designed to minimize the risk of the removal problems that plagued the first implantable contraceptive to become available in North America, Wyeth Pharmaceutical's Norplant.
Approved for sale in the U.S. in 1990, Wyeth stopped marketing the contraceptive here a decade later due to quality-control issues and a rash of lawsuits by women who said they were injured when having Norplant's six rods removed.
Wyeth also market's a two-rod implantable contraceptive outside the U.S. -- sold as Jadelle -- but has no plans to introduce it here, a company spokeswoman tells WebMD.
The newly published research review, conducted for the independent, health practices analysis group Cochrane Collaboration, found all three implantable contraceptives to be very effective for preventing pregnancy, but there were some differences between them.
Not surprisingly, the one-rod Implanon and two-rod Jadelle proved to be quicker to implant and remove from the body than the six-rod Norplant.
Menstrual bleeding irregularities were common with all three implants, but Implanon users were twice as likely as Norplant users to have complete cessation of periods after two years of use.
More Birth Control Options
Implantable contraceptives are just one of several new non-pill hormonal birth control options to become available to women in the U.S. within the past few years. Implanon joins the injectable contraceptive Depo-Provera, the contraceptive patch, a progestin-releasing vaginal ring, and a progestin-releasing intrauterine device, sold as Mirena.
Reproductive health researcher Lawrence Finer, PhD, says the new options are long overdue, but no one method is right for everyone.
Finer is the director of domestic research for the Guttmacher Institute, a reproductive health research and policy analysis group.
"The more birth control methods there are, the greater than chance that an individual woman will find a method that's a good fit for her," he says.
Finer says it is too soon to tell how many women in the U.S. are using Implanon. But he adds that acceptance of long-term birth control seems to be growing among American women, as evidenced by the increased use of the three-month, injected contraceptive Depo-Provera.
"People often ask me what the best birth control method is, but that is the wrong question," he says. "A better question is, 'What is the best birth control for me?' Hormonal or non-hormonal, long-term or every day -- the best option for one woman isn't necessarily the best for another."
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