NEW YORK (Reuters Health) - A growing number of U.S. women may be opting for intrauterine devices (IUDs) as their birth control method, a national survey finds.
That's good news, researchers say, since IUDs and contraceptive implants are the most effective forms of reversible birth control.
In the new study, researchers found that in 2009, 8.5 percent of U.S. women using birth control chose an IUD or implant - with the large majority going with the IUD.
That was up from just under four percent in 2007, according to findings published in the journal Fertility and Sterility.
"We saw some pretty notable growth," said lead researcher Lawrence B. Finer of the Guttmacher Institute in New York, a sexual and reproductive health organization.
It's not clear what's behind the shift, but a combination of factors are likely at play, Finer told Reuters Health.
One is that medical societies, like the American College of Obstetricians and Gynecologists (ACOG), have endorsed IUDs and implants.
ACOG says the devices should be offered as "first-line" options for most women, because of their effectiveness and safety.
Another reason, Finer said, is that advertisements have probably increased women's awareness of IUDs.
IUDs are implanted in the uterus, where they release small amounts of either copper or the hormone progestin to prevent pregnancy. The contraceptive implant, about the size of a matchstick, is inserted under the skin of the arm, where it releases controlled amounts of progestin.
The hormonal IUD, sold under the brand name Mirena, can prevent pregnancy for five years, while the copper version, sold as ParaGard, is effective for about 10 years. The contraceptive implant, sold as Implanon, works for three years.
Finer said the devices are "substantially" more effective than the Pill or condoms because they do not rely on perfect use.
"They are basically âset and forget' methods," Finer said.
With IUDs, it's estimated that between 0.2 percent and 0.8 percent of women will have an unplanned pregnancy within a year. The rate is just 0.05 percent with a contraceptive implant.
In contrast, the Pill and condoms must be used perfectly to be most effective. And with the way people typically use them, the unintended pregnancy rate is about nine percent per year.
With condoms alone, it's between 18 and 21 percent.
More could be done to encourage U.S. women to opt for IUDs and implants, according to Finer and his colleagues.
In some other countries, the devices are much more popular: in France and Norway, for example, about one-quarter of women on birth control use IUDs or implants. And in China, a full 41 percent do, Finer's team says in its report.