CHICAGO (AP) - Women should be able to keep an advance prescription of ``morning-after'' pills in their medicine cabinets to prevent pregnancy if they have unprotected sex, the new head of the American College of Obstetricians and Gynecologists says.

Dr. Thomas F. Purdon is asking the nation's 40,000 obstetrician-gynecologists to routinely offer women of childbearing age advance prescriptions for emergency contraceptives during checkups.

The call for advance prescriptions was being issued Monday at ACOG's annual meeting. Purdon, an Arizona gynecologist, is incoming president of the academy.

Half of all U.S. pregnancies, or about 3 million yearly, are unintended and more than a million of them end in abortion. Making emergency contraception readily available could potentially prevent a substantial number of these pregnancies, Purdon said in an interview last week.

``The impact is just incredible and I don't think that we've paid enough attention to it,'' he said.

It would allow women to stock their medicine cabinets with what are essentially high-dose birth control pills, to be used soon after unprotected sex.

``We know if it's in the house, women will use it more,'' said Dr. Anita Nelson, a Los Angeles-area ob-gyn who already offers advance prescriptions to her patients.

The hormone-containing pills have been available in the United States by prescription since 1998. Some birth control pills also can be used as emergency contraceptives if taken in high doses soon after sex.

The proposal to distribute the pills through advance prescriptions follows efforts by the academy and other groups to make emergency contraception available over the counter. Uncertainty over when, or even if, over-the-counter sales will be approved prompted the academy to push its alternative plan.

``Although over-the-counter approval by the FDA would be the broadest step to increase women's access to emergency contraception, we can't afford to delay other steps while we wait for this scenario to occur,'' said Purdon.

So far, neither maker of the two U.S. brands - Preven and Plan B - has asked the Food and Drug Administration to approve over-the-counter sales.

Plan B's makers are awaiting the outcome of research and probably will not seek over-the-counter approval until next year. Gynetics Inc., the maker of Preven, hopes to file for over-the-counter status within the next two years, Chairman Rod Mackenzie said.

The academy says only 1 percent of women have ever used the pills and many confuse them with the more controversial RU-486 abortion pill. Only 20 percent of ob-gyns routinely discuss the pills with patients.

Nelson said research has found pregnancy rates of half of 1 percent to 4 percent with Plan B, with the best results when used within 12 hours of sex.

The morning-after pills are available without a prescription in several European countries and in the state of Washington. Planned Parenthood offers women advance prescriptions at many of its clinics.

But many pharmacies don't stock them, and women typically have to call several before finding one that does, said Sharon Camp, founder and CEO of Women's Capital Corp., which makes Plan B.

The pills are designed to prevent conception by blocking the release of eggs from a woman's ovaries. If ovulation has already occurred when a woman has unprotected sex, they may also prevent the fertilized egg from implanting in the uterus. But the pills won't work if implantation has occurred.

That's the big difference between morning-after pills and RU-486, which causes a miscarriage if taken early in pregnancy. The Vatican opposes both, but other abortion foes have been less vocal on ``morning-after'' pills.

Copyright 2001 The Associated Press. All rights reserved.