Republican legislators in Colorado will not authorize funding for a program that gives free IUDs to low-income women — an effort that many believe was responsible for hugely driving down teen births.

Colorado has recently experienced a stunning decline in its teen birth rate. Between 2007 and 2012, federal data shows that births declined 40 percent — faster than any other state in the country.

State officials attributed part of this success to the Colorado Family Planning Initiative, which provided free IUDs to low-income women seen at 68 family planning clinics across the state. Last year, state officials estimated that young women served by those family planning clinics accounted for about three-fourths of the overall decline in Colorado's teen birth rate.

An anonymous donor had previously funded the program, but Democrats in the Colorado Senate added $5 million to the state budget to keep the program going in the future. That effort died in a Republican-controlled state Senate committee late last week, putting the program in peril.

As the Denver Post reported, the IUD program in Colorado "faced resistance from fiscal hawks who consider the spending redundant and social conservatives who believe IUDs cause abortions, a point rejected by the medical community."

Colorado officials, meanwhile, have vowed to keep moving forward with the program regardless of the roadblock.

"Where there’s a will, there’s a way," Larry Wolk, executive director of Colorado's Public Heath Department, told Colorado Health News. "We are going to go out and see if we can raise the money through private foundations. We already have some preliminary interest. We’re going to pull together a group of interested supporters in the next month and see what we can do."

Why IUDs are a way better contraceptive than birth control pills

Birth control pills, which have to be taken regularly, are susceptible to human error. The pill has a 6 percent failure rate. So out of 1,000 women taking birth control pills, 60 become pregnant in a typical year. Among women who use an IUD, between two and eight become pregnant (depending on the IUD type).

The American College of Obstetricians and Gynecologists recommends IUDs and the contraceptive implant (the one other long-acting, reversible contraceptive) as a "first-line" contraceptive that should be "encouraged as an option for most women."

But despite IUDs' incredible efficacy, few American women — just 8.5 percent of contraceptive users — choose this method. The devices tend to get an especially bad rap in the United States because of the Dalkon Shield, an early IUD from the 1970s that was hard to insert (it looked like this), sometimes failed to prevent pregnancy, injured as many as 200,000 women, and sometimes led to infertility or even death. All in all, it was a terrible contraceptive that was subsequently pulled from the market.

Today's IUDs are different: they're safer, easier to insert, and incredibly effective. That probably explains why 40 percent of gynecologists using a contraceptive are using IUDs — way more than the general population.