Colorado’s teen birth rate plummeted 40 percent between 2009 and 2013.

Since 2009, the state has provided 30,000 contraceptive implants or intrauterine devices (IUDs) at low or no cost to low-income women at 68 family-planning clinics across Colorado through the Colorado Family Planning Initiative. The effort was funded by a five-year commitment of $23 million from an anonymous donor.

At participating clinics, the percentage of young women receiving IUDs or implants quadrupled, according to a press release from Gov. John Hickenlooper (D).

The state attributes three-quarters of the overall decline in the Colorado teen birthrate to the program and said its success had a ripple effect.

With fewer unplanned pregnancies, the teen abortion rate fell by 35 percent between 2009 and 2012 in those counties where the initiative is in place.

The state also spent less on food programs for low-income mothers and children; infant enrollment in WIC supplemental nutrition program declined 23 percent between 2008 and 2013.

The governor’s office said the state saved $42.5 million in health-care expenditures associated with teen births.

For every dollar spent on the contraceptives, the state saved $5.68 in Medicaid costs, according to the Denver Post.

Liz Romer, a family-planning nurse at Children’s Hospital Colorado, told the BBC an IUD normally costs between $500 and several thousand dollars. She said that’s cost prohibitive to teens who don’t have the money themselves and feel they can’t ask their parents to pay. “It needs to be readily available, the same day, and it needs to be free,” she said.

But conservative religious groups disagree.

Carrie Gordon Earll, senior director of public policy for the conservative Christian ministry Focus on the Family, told the Denver Post she was skeptical of the state’s claim that increased access to contraception caused the decline in birthrates. “What we have seen over many years is that access to contraception does not equal fewer unintended pregnancies and fewer abortions,” Earll said. “Availability of contraception leads to increased sexual activity, which leads to unintended pregnancies and abortions.”

Bob Enyart, a spokesman for Colorado Right to Life, told the BBC offering contraception to teens sends the message that you can “have all the sex you want.”

“When you teach children that they’re animals — that they have evolved from pigs and dogs and apes — then they act like animals,” Enyart said.

Dainzu Mosqueda Salinas works for the Boulder Valley Women’s Health Center. She came to the clinic in 2010 as a teenager to get contraception. “One of my friends from school had an unplanned pregnancy, and at the time I was studying and was not looking to be pregnant,” Salinas told the BBC.

Colorado’s success is encouraging, but not every state has an anonymous millionaire willing to fund such a campaign. It’s not clear yet what will happen to Colorado’s program when the fortuitous funding stream runs out in 2015. However, a Colorado public health department spokesman told CNN the initiative is a useful model for family-planning coverage under the Affordable Care Act.

“By showing the effectiveness of long-acting, reversible contraceptives, we’re providing the evidence needed for health plans … to cover family planning services,” the spokesman said.

Correction: A previous version of this piece misspelled the name of Dainzu Mosqueda Salinas.