WASHINGTON (AP) -- Nearly four years after the government approved "morning-after" pills to help prevent unwanted pregnancies following unprotected sex, many women don't know about them and few doctors tell them such an option exists.

Widespread use of this method of emergency contraception could prevent millions of accidental pregnancies and hundreds of thousands of abortions, say women's and medical groups that are trying to publicize what they call the best-kept secret in female health care.

"It's impossible for people to get it unless they know about it," says Elizabeth Cavendish, legal director for the National Abortion and Reproductive Rights Action League.

Opponents, including the Roman Catholic Church, condemn it as a form of abortion because the pills, two doses taken 12 hours apart, may block a fertilized egg from implanting in the uterus.

"Its mode of action is to abort children, whose lives begin at conception," says Judie Brown, president of the American Life League. "Nobody admits that it causes abortion, and in fact it does."

Abortion rights advocates dispute that, noting the medical definition of pregnancy is when a fertilized egg attaches to the uterus.

The morning-after regimen also works by delaying the ovary's release of eggs or preventing a meeting of sperm and egg. High doses of standard birth-control pills work, too.

The pills must be taken within 72 hours of sex to work and are more effective when used as soon as possible.

Of the 6 million pregnancies in the United States every year, about half are unplanned, and about half of those are aborted.

Increased use of morning-after pills could cut the number of accidental pregnancies and subsequent abortions by up to half, says Princeton professor James Trussell, a reproductive health expert.

But many women don't know the pill exists and few doctors tell them, surveys find. Some women also confuse it with RU-486, the abortion pill used to terminate early pregnancies.

Less than half of American women know they can do something soon after having unprotected sex to reduce the risk of an unwanted pregnancy, according to a November 2000 survey by the Kaiser Family Foundation, a health care philanthropic organization, and Lifetime Television.

Among women ages 18-44, only 2 percent said they had ever used emergency contraception.

Only 6 percent of obstetrician-gynecologists and 5 percent of family practice doctors surveyed said they routinely discuss emergency contraception with patients.

"They're waiting for women to come in to ask, and women don't ask," says Trussell.

Others blame the health care system's focus on treating illness.

"We don't promote preventive health care as well as we should, and this is basically preventive health care," says Colleen Murphy, an ob-gyn in Anchorage, Alaska.

To counter that, some states and women's advocates are trying to boost awareness and get emergency contraception sold without a prescription, which is now required.

The earliest form of emergency contraception dates to 1974 and was nothing more than concentrated doses of standard birth-control pills.

The Food and Drug Administration approved two emergency contraception kits - Preven in September 1998 and Plan B in July 1999. They cost about $30 and have been shown to reduce the risk of pregnancy by up to 89 percent. Side effects include nausea and vomiting.

Some European countries allow the pills to be sold without a prescription and are more liberal about dispensing it.

School nurses in France may give the pills to girls in junior and senior high school. A supermarket chain in Britain began giving them away this year to women under 20 as part of a government-funded experiment to reduce teen-age pregnancy.

Last year, advocates asked the FDA to allow emergency contraception to be sold over the counter, saying the drugs are safer than aspirin. Opponents raised concerns about teen use and argued that women would abandon their regular method of birth control.

The FDA is reviewing the petition.

Meantime, some states are making it easier for women to get the pills after their regular contraception failed, they didn't use any or they were sexually assaulted.

In Alaska, California and Washington, women can skip the doctor's office and get morning-after pills from pharmacists who are authorized to dispense prescription drugs.

With pharmacies open weekends and sometimes 24 hours, women can take advantage of a contraceptive method that works best when taken quickly.

California has ordered HMOs in the state to pay for emergency contraception. Washington state requires hospital emergency rooms to offer it to rape victims.

The American College of Obstetricians and Gynecologists has urged members to offer prescriptions for emergency contraception during patients' regular checkups. For a fee, in addition to the cost of the pills, several Internet sites will forward a prescription to a nearby pharmacy after a doctor reviews a medical questionnaire the woman has filled out.

Proposals introduced in more than a dozen states call for emergency contraception for rape victims, pharmacy distribution, public education or some combination.

Bills in Congress propose similar steps but are not expected to pass this year.

Copyright 2002 The Associated Press. All rights reserved.