WASHINGTON - A half-century after the advent of the pill, the Obama administration on Monday ushered in a change in women's health care potentially as transformative: coverage of birth control as prevention, with no copays.

Services ranging from breast pumps for new mothers to counseling on domestic violence were also included in the broad expansion of women's preventive care under President Barack Obama's health care overhaul.

Since birth control is the most common drug prescribed to women, health plans should make sure it's readily available, said Health and Human Services Secretary Kathleen Sebelius. "Not doing it would be like not covering flu shots," she said.

Officials said the women's prevention package will be available Jan. 1, 2013, in most cases, resulting in a slight overall increase in premiums. Tens of millions of women are expected to benefit initially, a number that is likely to grow with time. At first, some plans may be exempt due to an arcane provision of the health care law known as the "grandfather" clause. But those plans could face pressure from their members to include the new coverage.

Earlier requirements under the health care law improved preventive coverage generally for people of both sexes.

Social and religious and religious conservatives objected to the birth control mandate, saying a conscience exception unveiled by the administration is insufficient.

Sebelius acted after a near-unanimous recommendation last month from a panel of experts at 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.

"Over a span of generations from grandmothers to granddaughters, we have come from birth control being a hope and a wish - and almost luck - to being recognized as a part of health care that improves women's health," said Cynthia Pearson of the National Women's Health Network, an advocacy group supporting the change.

Some public health experts predicted the change will promote the use of costlier long-acting contraceptives, such as hormonal implants. More reliable than the pill, they are gaining popularity in other economically advanced countries.

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 birth control.

A government study last summer found that birth control use is virtually universal in the United States. 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. Other 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.

"It's a step in the right direction, but it's not enough," said Jeanne Monahan, a policy expert for the conservative Family Research Council. As it now stands, the conscience clause offers only a "fig leaf" of protection, she added, because it may not cover all faith-based organizations.

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.

Other preventive services covered include:

-At least one "well-woman" preventive care visit annually.

-Screening for diabetes during pregnancy.

-Screening for the virus that causes cervical cancer for women 30 and older.

-Annual HIV counseling and screening for sexually active women.

-Screening for and counseling about domestic violence.

-Annual counseling on sexually transmitted infections for sexually active women.

-Support for breast feeding mothers, including the cost of renting pumps.

Aside from the conscience clause, the only other major exemption is for so-called "grandfathered" plans, many of which are offered by large employers. With time, however, many currently grandfathered plans are likely to lose that designation as they make routine changes affecting their benefits. Consumers should check with their health insurance plan administrator.