Denver — FOURTH-year medical student Megan Lederer recently helped deliver a premature baby at barely six months gestation. The newborn was tiny, unimaginably fragile, but she survived.

Caught up in the moment, Lederer didn't think about the implication for her chosen career. Later, though, she wondered: Could I have aborted that pregnancy?

She could have, she decided. She would have felt an obligation.

Lederer, 30, can't relate to the images that drew an older generation of physicians into abortion work. She can barely picture it when they talk about life before legal abortion: the blood-spattered apartments, the women racked with infection from stabbing sticks into their wombs.

But she and other young doctors-in-training have found their own motivation to enter a field that they know will put them at risk of isolation, harassment and hatred. For them, doing abortions is an act of defiance — a way of pushing back against mounting restrictions on a right they've taken for granted all their lives.

"It's like when your big brother says you can't do something," Lederer said. "That just makes you want to do it even more."

Abortion is one of the most common surgical procedures in the U.S., terminating about one in four pregnancies, not counting miscarriages. Yet the number of providers has fallen steadily for decades, dropping 37% between 1982 and 2000, the last year a census was taken. (During the same period, the number of abortions fell 17%.)

Antiabortion activists attribute the drop to a growing aversion to killing fetuses. "It's corrosive to the soul," said Douglas Johnson, legislative director for National Right to Life.

Abortion rights advocates counter with a litany of other reasons, starting with aggressive picketing of doctors, at work and, increasingly, at home. Physicians who choose to provide abortions also chafe at a lack of autonomy. In many states, every detail of their practice is regu-

lated: the width of clinic hallways, the number of air vents, even how often their staff must take physicals.

On the federal level, Congress has banned a particular technique for ending mid-term pregnancies, known by critics as "partial-birth abortion." The Supreme Court last month upheld that ban; doctors can be prosecuted for using the method even if they determine it's the safest approach for a given patient.

Listening to news of the Supreme Court's ruling, third-year medical student Lysie Cirona, 24, found herself shouting at her radio in frustration. Then she took a hard look at her career plans. She had always been interested in psychiatry, but now she envisioned herself flying to North Dakota or Nebraska a few times a month to perform abortions.

"It wasn't on my radar screen" a year ago, Cirona said, but her priorities have changed as she's learned more about the history and current state of abortion rights. Cirona has taken to badgering her professors to include information about abortion in their lectures. She attended workshops on how to respond effectively to antiabortion protesters.

Some days, she still wants to be a psychiatrist. Other days, she thinks of the women who drive 10 hours to reach the nearest abortion clinic. "This is what I'm going to do," she tells herself.

Her roommate at the University of Colorado, Michelle Cleeves, is also drawn to abortion work; simply voting for liberal politicians, she said, no longer seems like an adequate response to the abortion wars.

"It doesn't matter what you believe if you don't back it up with action," said Cleeves, 24. "The right to abortion doesn't mean anything if women don't have access."

NEARLY one-third of metropolitan areas and 97% of rural counties have no abortion providers, according to the Guttmacher Institute, a research group affiliated with Planned Parenthood. One in four patients must travel at least 50 miles to end a pregnancy.

Guttmacher researchers are working on updated statistics, but as of 2000, they reported that the United States had about 1,800 abortion providers — many of them near, or past, retirement age. By comparison, the American Medical Assn. reported that the same year, there were about 6,200 plastic surgeons, 9,700 dermatologists and 10,600 gastroenterologists.

Each spring, the advocacy group Medical Students for Choice brings several hundred students — nearly 90% of them women — to a weekend convention to nudge them into considering abortion work. One of the most effective tools: introducing them to veteran providers.