CreditPaul Rogers

Although teenage pregnancies and birthrates in the United States have been declining steadily since 1990, the nation still leads the developed world in these challenging statistics.

I say challenging because 82 percent of teen pregnancies and births are unplanned and nearly always unwanted. They often disrupt a girl’s education and life goals and sometimes result in shotgun marriages with poor long-term survival.

The falling pregnancy rate is not a result of a decline in teenage sexual activity, which experts say has remained steady for decades. Nor does abortion, which has dropped along with pregnancies, account for fewer teen births.

Rather, the data indicate that more teens now use contraception when they have sex. Still, too many fail to use the most effective methods or use them incorrectly or inconsistently, resulting in ill-timed or unwanted pregnancies. Even informed teenagers may have trouble accessing contraceptives: A new report by the Guttmacher Institute found that 24 states do not allow minors to receive contraceptives without parents’ permission.

Condoms, sold over-the-counter and sometimes distributed free in schools, are the most frequently used contraceptives by teens. But while key to preventing sexually transmitted infections, in practice condoms are among the poorest means to prevent pregnancy — better only than withdrawal. Currently, the most effective methods — so-called long-acting reversible contraceptives — are least often used by adolescents.

“Teens today get much more information about sexually transmitted diseases in school health ed classes than they do about pregnancy prevention,” according to Dr. Philippa Gordon, a pediatrician in Brooklyn, N.Y., who treats many adolescent girls and boys. “They don’t realize how very easy it is for a teenager to become pregnant. Just five to eight acts of unprotected sex would result in pregnancy. A girl can get pregnant even without having intercourse. Our biology is set up to foster it.”

Talking with adults about sex is often embarrassing for teenagers and challenging for their parents, who may leave it up to teachers and doctors to provide the necessary details. Indeed, some may be getting their information surreptitiously from watching pornography. Although schools may recognize the importance of preventing teenage pregnancy, they are often hampered by the mistaken belief that informing youngsters about contraception can encourage them to become sexually active.

However, Dr. David L. Hill tells parents, “Talking to kids about sex and even giving them condoms does not make them have sex any sooner. It does, however, lower the chances you’ll become a grandfather before you’re ready.”

The fact is, with or without sex ed, about half of high school seniors have already become sexually active and need accurate, up-to-date information and access to effective contraception. Furthermore, teenagers who are not adequately informed about pregnancy prevention, or are told only about abstinence, are more likely to become pregnant than those told about birth control options, including emergency contraception, and how to get them. Cost may be a factor.

Many adolescents planning on abstinence do not remain abstinent. As Dr. Hill wrote on the website, “The best studies of adolescents who take a ‘virginity pledge’ suggest that these kids have sex just as early as those who don’t pledge, but that they are less likely to use birth control when they do have sex.”

Recognizing this, both the American Academy of Pediatrics and the American College of Obstetricians and Gynecologists (ACOG) have urged their members to have “comprehensive” conversations with adolescent patients about their reproductive health and their contraceptive needs, knowledge and concerns.

Dr. Karen Gerancher, author of a recent ACOG opinion article on counseling adolescents about contraception, said, “When we’re able to reach patients before they become sexually active, or early in their sexually active life, we empower them to take control of their reproductive health, and prevent sexually transmitted infections and unintended pregnancies that could permanently impact the future they’ve envisioned for themselves.”

Although many adolescent girls choose birth control pills, as typically used they are not most effective in preventing pregnancy. Here’s what teens should know about contraceptive options, in order of effectiveness.

The implant. This long-acting reversible contraceptive is a matchstick-size flexible plastic rod that a doctor inserts under the skin, usually in the upper arm, where it can prevent pregnancy for at least three years, at which time it should be replaced. It contains a progestin hormone that blocks the release of an egg from the ovary. It is the most effective means of birth control, with a one-year failure rate significantly less than one in 100 (0.05 percent). Fertility typically returns quickly once the implant is removed.

An IUD. This other long-acting reversible contraceptive has a slightly higher failure rate of 0.2 to 0.8 percent. A doctor inserts the small T-shaped device into the uterus, where it prevents sperm from fertilizing an egg. There are two types: the Copper T IUD that has no hormone and needs to be replaced only once in 10 years, and a progestin-containing IUD that is replaced every three to five years.

Progestin injection. This shot of a progestin prevents the release of an egg from the ovaries for three months. Its failure rate is six in 100 within the first year.

Vaginal ring. This hormone-containing ring is placed once a month by the user into her vagina, where it prevents release of an egg for three weeks. It is then removed for one week to permit menstruation. During one year of use, about nine women in 100 will get pregnant with this method.

The patch. The patch contains a hormone that is absorbed through the skin to block release of an egg. It is replaced weekly for three weeks, followed by a week off to allow for menstruation. Like the ring, it has a 9 percent failure rate.

The pill. This too has a 9 percent failure rate within the first year of use. The pill must be taken daily, and inconsistent use is the usual reason it fails. There are two types, but only the one containing two hormones, an estrogen and a progestin, is usually prescribed for teens.

Condom. This is the only method that can prevent sexually transmitted infections and should always be used with any of the other methods. The male condom, a thin sheath that slips over the penis, has a pregnancy rate of 18 percent. The female condom, or vaginal pouch, has a failure rate of 21 percent, comparable to that of withdrawal, which has a 22 percent failure rate.

Emergency contraception. These progestin-containing pills, to be taken within five days (the sooner the better) when contraception is not used or a condom breaks, are available over-the-counter, even for teens.

ACOG recommends that teens keep emergency contraception on hand “just in case” to maximize its effectiveness.