Dr. Iglesia said the argument for changing Pap screening was more compelling than that for cutting back on mammography  which the obstetricians’ group has staunchly opposed  because there is more potential for harm from the overuse of Pap tests. The reason is that young women are especially prone to develop abnormalities in the cervix that appear to be precancerous, but that will go away if left alone. But when Pap tests find the growths, doctors often remove them, with procedures that can injure the cervix and lead to problems later when a woman becomes pregnant, including premature birth and an increased risk of needing a Caesarean.

Still, the new recommendations for Pap tests are likely to feed a political debate in Washington over health care overhaul proposals. The mammogram advice led some Republicans to predict that such recommendations would lead to rationing.

Senator Tom Coburn, a Republican from Oklahoma who is also a physician, said in an interview that he would continue to offer Pap smears to sexually active young women. Democratic proposals to involve the government more deeply in the nation’s health care system, he said, would lead the new mammography, Pap smear and other guidelines to be adopted without regard to patient differences, hurting many people.

“These are going to be set in stone,” Mr. Coburn said.

Senator Arlen Specter, a Pennsylvania Democrat and longtime advocate for cancer screening, said in an interview: “And this Pap smear guideline is yet another cut back in screening? That is curious.” Mr. Specter, who was treated for Hodgkin’s lymphoma in 2005 and 2008, said Congress was committed to increasing cancer screenings, not limiting them.

Representative Rosa DeLauro, Democrat of Connecticut, said that the new guidelines would have no effect on federal policy and that “Republicans are using these new recommendations as a distraction.”