What’s the Most Effective Method of Contraception, by Far?

Health and medicine explained.
July 31 2012 11:30 AM

Why Have Teen Pregnancy Rates Dropped?

A new study shows how to reduce them even more.

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Photograph courtesy of iStockphoto/thinkstockphotos.

Something quite remarkable has happened to teenage pregnancy rates in the past few years. They’ve reached a three-decade low, down by 40 percent since 1990. Teen births and abortions also have fallen respectively by one-third and one-half.

Better sex education, though a sensible practice, doesn’t deserve the full credit. Teen pregnancy is often blamed on some states’ promotion of school-based “abstinence-only” education, which neglects contraception. But the recent drops in teen pregnancy were present across the country, in states with comprehensive sex education (like New Jersey, where annual teen pregnancy rates dropped from 11 percent to 7 percent) and those without it (like Texas, where the rate is higher but fell by about the same relative amount). The Centers for Disease Control and Prevention reports that 40 percent of teens didn’t use a condom at last intercourse, and that sorry figure doesn’t vary much by state. And between 1995 and 2010, depressingly, the substantial percentage of teens who used no contraception at all remained unchanged nationwide, indicating that teens didn’t suddenly start using birth control.

Part of the explanation is that teenagers are waiting longer to have sex. According to federal surveys of teenage girls, 49 percent reported they were virgins in 1995, but 57 percent said they were in 2010. (The trend was even more pronounced among black teens, whose rate of abstinence rose from 40 percent to 54 percent.) However, these modest changes don’t fully explain the dramatic drop in teen pregnancy.

So what really changed? Even though the same proportion of teens has used birth control during the past 20 years, the key to lower pregnancy rates has been a shift from condom use alone to more effective hormonal methods like the pill. It turns out that not all contraception is the same. No matter how well-educated they are, teens who do use birth control can’t reliably use condoms every time. To be sure, condoms prevent sexually transmitted diseases and are an important public health tool. But we now realize they should never, ever be the sole method of birth control for teens. They find condoms too much of hassle to use time after time—so they don’t.

Recognizing that condoms have a high risk of failure due to noncompliance, public health authorities and doctors encouraged more girls to get the pill. That quiet revolution has caused a major decline in unwanted pregnancies.

Still, despite the progress, 7 percent of all teenage girls get pregnant each year. In fact, half of all American pregnancies, regardless of a woman’s age, are unplanned, leading to more than a million abortions annually.

We’ve learned that some kinds of contraception are more prone to human error than others. But have we taken the lesson to heart? Half of the 3 million annual unintended pregnancies at any age in the United States occur among people using birth control. The pill is the most popular method, used by more than half of all women trying to avoid pregnancy. People believe it is highly reliable because it is over 99 percent effective when “used correctly” in supervised drug trials.

And therein lies the catch. In the real world, only 40 percent of adults and 25 percent of teens actually remember to take the pill every day, which makes the real-world risk of pregnancy much higher than expected.

Earlier this year, Washington University researchers led by Jeff Peipert reported in the New England Journal of Medicine that 5 percent of women in a study who were on the pill got pregnant within a year. Among those under 21 years of age, almost twice as many did. Take a moment to reflect on that. Imagine you are a concerned parent who accepts that your high school senior has sex. You take her to the doctor and she starts taking the pill. The data show that this is much better than just telling her to use a condom during intercourse. However, before graduation, 1 in 10 such girls will be headed for the delivery room or abortion clinic. That is a breathtaking failure rate.

Peipert’s study included almost 10,000 women given their choice of free contraception. It was funded not by federal grants (which almost never pay for contraception research), but by a private foundation endowed by the iconoclastic wife of investor Warren Buffett. The study points a clear way forward for reducing unwanted pregnancies. To begin with, when contraception was free, almost three-quarters of teens and adult women chose intrauterine devices like Mirena or ParaGard, which last five to 10 years, over alternatives like the pill, contraceptive patch, cervical ring, or Depo-Provera. (Modern IUDs can be implanted easily in young teens and do not carry additional risks of pelvic infection.) Similarly, IUD adoption doubled in California when the devices were made free.

But the most dramatic result of Peipert’s study was that the risk of contraceptive failure was 22 times higher with the pill than with IUDs in adult women, and double that for teens. Just imagine, Peipert recently told me, if a miracle drug suddenly slashed cancer deaths or heart attacks by 95 percent. Every patient would demand it and no one would want the older therapies. The parent in the above example would sleep better at night knowing the teen’s risk of pregnancy was only 0.3 percent, instead of 10 percent. However, only 2 percent of teens and 4 percent of American women now get IUDs. More couples than that rely on withdrawal, which has an estimated 25 percent risk of failure, as their preferred contraceptive method.

Peipert makes another persuasive argument. Though this aspect of his research is still in peer review and awaiting publication, he suspects that the abortion rate can drop by half when women are given free access to IUDs. Again, imagine if a magic treatment suddenly made half the country’s abortions unnecessary. For what good reason would anybody be opposed?

Vermont provides a good example of how contraception research can improve public health. The state has the country’s lowest teen pregnancy rate and highest use of teen contraception. Breena Holmes, a pediatrician who directs the state’s department of maternal and child health care, points out that the American Congress of Obstetricians and Gynecologists still doesn’t promote the massive advantages of IUDs over the pill. Though Medicaid covers IUDs, there’s usually only a one-time payment, which may be insufficient for follow-up care. (For example, many women may have spotting and might require a subsequent pelvic exam or other testing, although the problem generally improves a few months after implantation.) To get around these obstacles, Holmes explains, Vermont engineered innovative federal payment schemes in association with Planned Parenthood to expand reproductive health services and dismantle barriers to IUD availability.

For decades, battles over reproductive health in teens have focused on sex ed in schools. But the decline in teen pregnancy since 1990 shows that the big changes occur only when we also treat reproductive health just like every other kind of medical science—by discarding problematic treatments and aggressively promoting effective ones.

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