Women on birth-control pills, the vaginal ring or the patch have a 20-fold higher risk of becoming unintentionally pregnant compared to those on IUDs (intrauterine devices) or implants, i.e. longer-acting forms of birth control, researchers from Washington University School of Medicine in St. Louis reported in NEJM (New England Journal of Medicine).

Birth-control pills can be very effective, as long as there is excellent compliance, i.e. if the woman taking then remembers to do so every day.

The authors found that short-term contraceptive methods, including birth-control pills, the ring or the patch were particularly unreliable among younger females – women aged under 21 years are twice as likely to become unintentionally pregnant compared to older ones.

The researchers believe that the number of unplanned pregnancies among adolescent females in the USA would drop significantly if more of them went onto longer-acting contractive methods.

Senior author Jeffrey Peipert, MD, said:

“This study is the best evidence we have that long-acting reversible methods are far superior to the birth-control pill, patch and ring. IUDs and implants are more effective because women can forget about them after clinicians put the devices in place.”

Approximately half of all pregnancies in the USA are unintended ones – a total of 3 million every year. There are significantly more unwanted pregnancies in America compared the totals in other industrialized nations. According to previous studies, approximately half of all these pregnancies happen because of contraceptive failures.

Intrauterine devices are placed in the female’s uterus by a health-care professional. The hormonal IUD lasts for five years, while the copper IUD can last for twice as long. Hormonal implants, which are placed under the skin of the upper arm, provide contraception for 36 months.

These long-term contraceptive methods, although very effective, can involve upfront costs of over $500; something many American women cannot afford.

Lead author Brooke Winner, MD, said:

“We know that IUDs and implants have very low failure rates – less than 1 percent. But although IUDs are very effective and have been proven safe in women and adolescents, they only are chosen by 5.5 percent of women in the United States who use contraception.”

The team had set out to determine whether educating females regarding the effectiveness of different contraceptive methods might result in fewer unintended pregnancies if they did not have to consider costs. All the women in this study were provided with birth control free-of-charge.

The study included over 7,500 women, aged from 14 to 45 years; they were all at high risk of unintended pregnancy. All the females had enrolled in the Contraceptive CHOICE project. They were all either sexually active, or intended to become sexually active within six months. They were either wishing to change birth control methods, or were not on any kind of contraception. None of the women wanted to become pregnant for the next year.

The following birth control methods were explained to the women; they could choose which one they wanted:

  • Vaginal ring
  • Patch
  • IUD
  • Implant
  • Contraceptive injection
  • Birth-control pills

Whenever they wished, the participants could either discontinue or change contraceptive methods.

During the study, the women were contacted by telephone every three or six months and asked whether they had missed any periods and/or whether they had become pregnant. Participants who wondered whether they might be pregnant were invited to come in for a urine pregnancy test. The ones who were pregnant were asked whether they had intended to do so and what contraceptive method they had been using, if any.

334 women became pregnant over the 36-month study period.

  • 156 pregnancies occurred because the contraceptive method had failed
  • 133 (4.55%) of those on the pill, ring or patch had contraceptive failure
  • 21 (0.27%) of those on implants and IUDs had contraceptive failure

Winner said:

“This study also is important because it showed that when IUDs and implants are provided at no cost, about 75 percent of women chose these methods for birth control.”

Women with public health insurance, those who already have had children, and older ones are more likely to opt for implants or an IUD. Those on private health insurance, as well as women who have never had any children are more likely to chose the ring, the patch or birth-control pills.

Winner said:

“If there were a drug for cancer, heart disease or diabetes that was 20 times more effective, we would recommend it first. Unintended pregnancies can have negative effects on women’s health and education and the health of newborns.”

Written by Christian Nordqvist