(RxWiki News) The only way to be absolutely sure you don't get pregnant is certainly not to have sex. But if you are sexually active, do you know which contraception is most effective?
The top most effective forms of birth control appear to be IUDs (intrauterine devices) and implants, according to a recent study showing that they exceed pills, patches and rings in preventing pregnancy.
"Talk to your doctor about the right contraceptive method for you."
Brooke Winner, MD, a resident in obstetrics and gynecology at Barnes-Jewish Hospital in St. Louis, and colleagues wanted to find out which method was most likely to prevent a pregnancy, considering that about half of all pregnancies in the U.S. each year are unplanned.
Winner and colleagues included 7,486 women, aged 14 to 45, from the St. Louis area in their study. The women were identified as being at high risk of unintended pregnancy and were either sexually active or planning to become sexually active within six months.
The participants all stated they did not want to become pregnant for the next year and were either not currently using contraception or wanted to switch to a different birth control than they were currently using.
After receiving counseling and information about birth control methods, the women chose to go with an IUD, an implant, birth control pills, the patch, a vaginal ring or a contraceptive injection, such as Depo-Provera.
The counseling included information on each method's effectiveness, possible side effects, and the risks and benefits of each. Whichever method they chose was provided free of charge.
Three months into the study, the participants were interviewed by phone about whether they had missed periods or might be pregnant. If they were, they came in for a pregnancy test and, if pregnant, were asked whether it was intentional and what contraception they were using, if any.
The researchers conducted these phone interviews again six months into the study and then every six months throughout the complete study, which ran from August 2007 through September 2011.
A total of 334 women became pregnant, and 156 of these were because of contraception that had failed. Of the women whose birth control method didn't prevent pregnancy, 133 were using the pill, the patch or the ring, compared to 21 who were using IUDs or implants.
The researchers calculated that women using pills, the patch or a ring were about 20 times more likely to become pregnant despite using birth control than women who had an IUD or an implant.
The women most susceptible to unintended pregnancies with the pills, patch or ring were those under age 21, who were twice as likely as older women to get pregnant using these methods. This may be because these methods require the woman to remember to take the pill or replace the patch or ring.
"IUDs and implants are more effective because women can forget about them after clinicians put the devices in place," said senior author Jeffrey Peipert, MD, a professor of obstetrics and gynecology at the school.
Because past studies asked women what method they were using rather than providing them with a paid for choice of methods, this study also revealed the choices women make with contraception when price is not a factor.
Although only 5.5 percent of women in the U.S. choose IUDs for their contraception, the rate was far higher in this study when the method was free to participants.
"When IUDs and implants are provided at no cost, about 75 percent of women chose these methods for birth control," Winner said. "We know that IUDs and implants have very low failure rates —less than 1 percent."
The cost for an IUD is usually around $500, which generally covers the cost of the device but may not cover the office visit or doctor's fee for insertion. An IUD is a T-shaped device inserted by a doctor into the cervix.
Two types of IUDs exist. IUDs with a small amount of hormone in them remain in a woman's cervix for five years or until she has it removed. Copper IUDs, which create an irritation that prevents an egg from implanting in the uterus, can remain for up to 10 years.
Implants contain hormones and are inserted under the skin of the upper arm, where they can remain up to three years. These cost approximately $400 to $800.
By comparison, birth control pills cost about $10 to $50 a month, depending on whether a person has insurance and which pill they take. The patch and the ring both cost $15 to $80 a month.
The study was published in the May 24 issue of the New England Journal of Medicine. The research was funded by the Susan Thompson Buffet Foundation.
Dr. Peipert has received compensation for expert testimony regarding blood clots from the vaginal ring and has received fees or royalties from Omnia Education, Merck and Lippincott. Another author has received lecture fees from Bayer.