Contraceptive implants are placed under the skin, typically in a woman's upper arm, and slowly release hormones.

In the U.S., the only contraceptive implant available contains the progestin hormone etonogestrel and is marketed under the brand name Implanon. It's about the size of a matchstick and can prevent pregnancy for up to three years after implantation.

Theoretically, immediately after having a baby is an ideal time for young mothers to get a contraceptive implant -- but data on how well that strategy works are rare, according to lead researcher Dr. Kristina M. Tocce, from the University of Colorado, Denver School of Medicine in Aurora.

She and her colleagues reported in the American Journal of Obstetrics and Gynecology that for every 100 adolescents who become pregnant, between 12 and 49 will get pregnant again within a year. And compared to a teenager's first birth, her second almost triples the risk of preterm delivery and stillbirth.

The U.S. Medical Eligibility Criteria for Contraceptive Use assign a Category 1 rating to the etonogestrel implant in adolescents -- meaning there are no restrictions on its use.

The new findings are from a study of adolescents in a prenatal and postnatal counseling and treatment program, including 171 young mothers who opted for getting the implant inserted immediately after giving birth and 225 who elected to use other contraceptive methods.

All of the mothers expressed a desire to prevent pregnancy for at least a year after giving birth.

Merck, which makes Implanon, advises that the implant should be inserted four weeks after women who are breastfeeding have given birth, and says a small amount of the hormone passes into breast milk.

The researchers said they informed all the young mothers in their study that the immediate-implant strategy differs from the package insert recommendations.

Six months later, 156 mothers in the implant group -- almost 97 percent -- had kept using the implants; at 12 months, 132 -- 86 percent -- still had the implants in.

Some women said they stopped using the hormonal implants because of irregular periods.

At six months, none of the implant mothers had become pregnant, compared to 21, or one in every 10, of those who opted to use other contraceptive methods.

And at one year, four mothers in the implant group and 38 in the comparison group had become pregnant again.

Of the four pregnancies in the implant group, one was due to implant failure. The other three happened after women had the implant removed.

Given the success of the approach, Dr. Tocce told Reuters Health in an email that hospitals and insurance companies that make women wait to get an implant "should reevaluate their policies to facilitate the avoidance of repeat pregnancy in adolescent mothers."

One limitation for some women may be price: The implant costs between $400 and $800, including the doctor's fee for insertion.

But that's a one-time fee and negates the need for regular purchases of birth control pills or condoms, researchers have pointed out. Birth control pills, for instance, cost anywhere from about $10 to $50 a month, depending on whether they're generic or brand-name pills.

"I would like to see (the implant) become standard of care," Tocce concluded. "It certainly should be an option for those who want it."

SOURCE: bit.ly/LQDswd American Journal of Obstetrics and Gynecology, online April 18, 2012.

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