One of Obamacare's biggest selling points for women is the guarantee of no-cost birth control, a new benefit that includes all forms of contraception from the pill to tubal ligation.

But two years after the rules eliminating copayments for contraceptives took effect, some women are still forking over cash to the pharmacist when they pick up their pills or at the doctor's office when they obtain other forms of birth control.

Just last week, CVS announced it would send rebates to 11,000 women who were erroneously charged for their birth control pills at the company's stores because of a computer error. The snafu came to light when an aide to Rep. Jackie Speier (D-Calif.) had to pay $20 for birth control at a Washington CVS, which prompted an inquiry by the lawmaker.

So did President Barack Obama break a promise? Are health insurance companies and drugstores picking women's pockets?

The good news is that neither of those things is true, and eventually almost all women with health coverage won't have to pay a dime when they obtain contraceptives. The bad news is that it's a little complicated. Because of course it is. This is the American health care system, after all.

"American women don't really know what all the rules are," said Judy Waxman, vice president for health and reproductive rights at the National Women's Law Center. "All this is relatively new, and it's working fairly well. It just needs to be cleaned up and work better."

Some health insurance plans aren't yet required to comply with this part of Obamacare. Others never will have to cover birth control, such as those plans provided to employees of religious organizations. And as the CVS example illustrates, sometimes insurers and pharmacists just get it wrong, and women have to jump through hoops to set it straight.

"We do hear from women all over the country with what I will call glitches," Waxman said. "Not everybody understands what they're supposed to be doing."

First, the basics: The Affordable Care Act does require health insurance companies to cover all Food and Drug Administration-approved contraceptives -- including the pill, IUDs, the ring and the patch -- without any form of cost-sharing like copayments or deductibles. This requirement comes from the same part of the law that mandates no charges for preventive medicine, such as immunizations and cholesterol tests.

If you receive your health benefits from an employer and you're not sure whether you have to pay out-of-pocket to get contraception, you should ask a manager, the human resources office or the insurance company. If you buy health insurance on your own, check with the plan to find out what your contraceptive coverage is. All health insurance sold on the Obamacare exchanges includes no-cost birth control. If your insurance company still insists you owe copayments, you might have to file an appeal, Waxman said.

If you don't get straight answers from your employer or insurance provider, or if you feel like you're being ripped off, organizations such as the Planned Parenthood Action Fund and the National Women's Law Center can help, as can state insurance commissioners and the U.S. Department of Labor, Waxman said.

Despite its shortcomings and the confusion around how it's supposed to work, the Obamacare birth control mandate has had a huge impact: Many, many more women have access to no-cost contraception than before the law took effect, as this chart from the Guttmacher Institute, a reproductive health research organization, shows.


Source: The Guttmacher Institute

The share of women who obtained oral contraceptives without copayments rose from 15 percent in 2012 to 67 percent this year, according to a survey by the Guttmacher Institute. Women who used an injectable contraceptive or the ring saw a similarly major improvement in their benefits, and those using IUDs saw a somewhat smaller increase.

The effect on women's pocketbooks is striking: Women using contraceptives saved $483 million in copayments last year, according to IMS Institute for Healthcare Informatics, a branch of IMS Health that tracks pharmaceutical sales. (Obamacare didn't exactly make contraceptives "free," of course, because their cost now just gets included in the overall insurance cost.) The number of prescriptions filled for the pill also increased by 4.6 percent from the year before, IMS reported in April.

Top bar in millions of prescriptions. Bottom bar in millions of dollars. Source: IMS Institute for Healthcare Informatics

That's probably a big reason why this part of Obamacare is so popular. In a survey conducted this July, 60 percent of people said they supported mandated no-cost birth control, the Henry J. Kaiser Family Foundation found. Still, one-third of Americans didn't know about the no-cost birth control benefit as recently as March, and only one-fifth said they'd heard a lot about it