That could start a shift toward more reliable - and expensive - forms of birth control that are gaining acceptance in other developed countries.
But first, look for a fight over social mores.
A panel of experts advising the government meets in November to begin considering what kind of preventive care for women should be covered at no cost to the patient, as required under President Obama's overhaul.
Sen. Barbara Mikulski, the Democrat who is author of the women's health amendment, says the clear intent was to include family planning.
But is birth control preventive medicine?
Conflicting answers frame what could be the next clash over moral values and a health law that passed only after a difficult compromise restricting the use of public money for abortions.
For many medical and public health experts, there's no debate.
"There is clear and incontrovertible evidence that family planning saves lives and improves health," said obstetrician-gynecologist Dr. David Grimes, an international family planning expert who teaches medicine at the University of North Carolina. "Contraception rivals immunization in dollars saved for every dollar invested. Spacing out children allows for optimal pregnancies and optimal child rearing. Contraception is a prototype of preventive medicine."
But U.S. Catholic bishops say pregnancy is a healthy condition, not an illness. In comments filed with the Department of Health and Human Services, the bishops say they oppose any requirement to cover contraceptives or sterilization as preventive care.
"We don't consider it to be health care, but a lifestyle choice," said John Haas, president of the National Catholic Bioethics Center, a Philadelphia think tank whose work reflects church teachings. "We think there are other ways to avoid having children than by ingesting chemicals paid for by health insurance."
So far, most other religious conservatives have stayed out of the debate, though that could change. Some say they are concerned about any requirement that might include the morning-after pill. The Food and Drug Administration classifies it as birth control; some religious conservatives see it as an abortion drug.
Jeanne Monahan, a health policy expert at the conservative Family Research Council, said her group would oppose any mandate that lacks a conscience exemption for moral and religious reasons. She said there's "great suspicion" that a major abortion provider, Planned Parenthood, is leading the push for free birth control.
As recently as the 1990s, many health insurance plans didn't even cover birth control. Protests, court cases, and new state laws led to dramatic changes. Today, almost all plans now cover prescription contraceptives. So does Medicaid, the health care program for low-income people.
The use of birth control is "virtually universal" in the U.S., according to a government report this summer from the National Center for Health Statistics. Nearly 93 million prescriptions for contraceptives were dispensed in 2009, according to IMS Health, a market analysis firm. Generic versions of the pill are available at Walmart stores, for example, for $9 a month.
Still, about half of all pregnancies are unplanned, and many occur among women using some form of contraception. The government says the problem is rarely the birth control method, but "inconsistent or incorrect use," such as forgetting to take a pill.
Advocates say free birth control would begin to address the problem.
"We can look at other countries where birth control is available for no cost, and what we see are lower pregnancy rates, lower abortion rates and lower teen pregnancy," said Cecile Richards, president of Planned Parenthood.
It would remove a cost barrier that may be keeping women away from more reliable long-acting birth control, and also affects those who don't do well on inexpensive generics.
A major research study now taking place in St. Louis provides a glimpse of how things might change.
The Contraceptive CHOICE Project is providing free birth control to as many as 10,000 women, tracking their decisions and the results. About 70 percent have chosen long-acting contraceptives such as IUDs (intrauterine devices) or implants, which are reversible and have a much lower failure rate than pills or condoms. The proportion of U.S. women using such methods remains low; part of the reason seems to be higher upfront cost.
"The shift we need to see in the United States is a shift away from methods like the pill and condoms to the most effective methods, like implants and IUDs," said Dr. Jeffrey Peipert, a principal investigator on the study. "And we'll only see that shift if somebody is willing to pay for it."
How the Obama administration will apply the law remains to be seen. It could allow insurance plans wide discretion on meeting the coverage requirement. A panel convened by the Institute of Medicine will hold its first meeting Nov. 16 to begin work on recommendations to HHS. The department has until next August to make its decision.