WASHINGTON (AP) — Health insurance plans must cover birth control as preventive care for women, with no copays, the Obama administration said Monday in a decision with far-reaching implications for health care as well as social mores.

The requirement is part of a broad expansion of coverage for women's preventive care under President Barack Obama's health care law. Also to be covered without copays are breast pumps for nursing mothers, an annual "well-woman" physical, screening for the virus that causes cervical cancer and for diabetes during pregnancy, counseling on domestic violence, and other services.

"These historic guidelines are based on science and existing (medical) literature and will help ensure women get the preventive health benefits they need," said Health and Human Services Secretary Kathleen Sebelius.

The new requirements will take effect Jan. 1, 2013, in most cases. Over time, they are expected to apply to most employer-based insurance plans, as well as coverage purchased individually.

Sebelius acted after a near-unanimous recommendation last month from a panel of experts convened by the prestigious Institute of Medicine, which advises the government. Panel chairwoman Linda Rosenstock, dean of public health at the University of California, Los Angeles, said that prevention of unintended pregnancies is essential for the psychological, emotional and physical health of women.

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 cover prescription contraceptives — with varying copays. Medicaid, the health care program for low-income people, also covers contraceptives.

Indeed, a government study last summer found that birth control use is virtually universal in the United States, according to a government study issued last summer. More than 90 million prescriptions for contraceptives were dispensed in 2009, according the market analysis firm INS health. Generic versions of the pill are available for as little as $9 a month. Still, about half of all pregnancies are unplanned. Many are among women using some form of contraception, and forgetting to take the pill is a major reason.

Preventing unwanted pregnancies is only one goal of the new requirement. Contraception can help make a woman's next pregnancy healthier by spacing births far enough apart, generally 18 months to two years. Research links closely spaced births to a risk of such problems as prematurity, low birth weight, even autism. Research has shown that even modest copays for medical care can discourage use.

In a nod to social and religious conservatives, the rules issued Monday by Sebelius include a provision that would allow religious institutions to opt out of offering birth control coverage. However, many conservatives are supporting legislation by Rep. Jeff Fortenberry, R-Neb., that would codify a range of exceptions to the new health care law on religious and conscience grounds.

Although the new women's preventive services will be free of any additional charge to patients, somebody will have to pay. The cost will be spread among other people with health insurance, resulting in slightly higher premiums. That may be offset to some degree with savings from diseases prevented, or pregnancies that are planned to minimize any potential ill effects to the mother and baby.

The administration did allow insurers some leeway in determining what they will cover. For example, health plans will be able to charge copays for branded drugs in cases where a generic version is just as effective and safe for the patient.

The requirement applies to all forms of birth control approved by the Food and Drug Administration. That includes the pill, intrauterine devices, the so-called morning-after pill, and newer forms of long-acting implantable hormonal contraceptives that are becoming widely used in the rest of the industrialized world.

Coverage with no copays for the morning-after pill is likely to become the most controversial part of the change. The FDA classifies Plan B and Ella as birth control, but some religious conservatives see the morning-after drugs as abortion drugs. The rules HHS issued Monday do not require coverage of RU-486 and other drugs to chemically induce an abortion.

Advocates say the majority of women will be covered once the requirement takes effect in 2013, although some insurance plans may opt to offer the benefit earlier. Aside from the religious conscience clause, there is one additional exception. Plans that are considered "grandfathered" under the law will not be affected, at least initially. Consumers should check with their health insurance plan administrator.