CHICAGO — For bleary-eyed new moms, the image of Paula Radcliffe celebrating her astonishing New York marathon victory just nine months after giving birth is more than slightly surreal.

There she was, one sinewy arm holding a baby, the other victoriously waving a British flag, ribs visible beneath a washboard-flat torso, not an ounce of visible fat on her sleek body.

"Running whilst preggers? Winning 9 months after? Yo!" read one blog comment.

"She is phenomenal and a role model to all new Mums!" said another.

Radcliffe's triumph last week, running 26.2 miles in two hours, 23 minutes, just 291 days after childbirth, inspires equal amounts of awe and envy.

But it also highlights a medical debate about just how gung-ho women should be about exercise during pregnancy and afterward.

Some doctors believe women used to rigorous exercise can continue it at least early in pregnancy and resume soon afterward, but that this is not the time for inactive women to suddenly decide they want to try a marathon. Their advice is often that it's OK to continue what you're used to, but don't push it.

Other doctors are "pretty nervous about women exercising during pregnancy" and advise against, said Dr. Linda Szymanski, a Johns Hopkins obstetrician and exercise specialist.

The problem is, guidelines are vague and there's not much research, she said.

Most medical advice on the topic is based on "pretty poor evidence," and there's even less data on the effects in highly trained athletes, Szymanski said. "It's a really tough area."

Running a marathon requires several months of training and long-distance running most days. The intensity is rigorous for those hoping to win.

Radcliffe ran throughout her pregnancy and has said her husband's help made training afterward easier. The British runner also has said she resumed training too soon after a long and difficult labor. She suffered a stress fracture at the base of her spine that sidelined her in May for eight weeks.

Still, the 33-year-old women's marathon world record-holder is a seasoned pro who won six previous marathons. So for her, running during pregnancy and afterward made sense, said Dr. Alan Peaceman, chief of maternal-fetal medicine at Northwestern University's Feinberg School of Medicine in Chicago.

Kristen Chase of Atlanta, who had a baby son two days after Radcliffe's daughter was born in January, was a several-times-weekly jogger before pregnancy. She said her doctor told her she could start exercising again when her son was six weeks, "but not to do anything strenuous."

That would definitely rule out training for a marathon — not that Chase was contemplating it.

"New moms are extremely tired, so the prospect of getting on a treadmill or even running outside at six weeks when your children — at least my children — aren't sleeping through the night" seems unimaginable, said Chase, who also has a 3-year-old daughter.

Except for women who have had a Caesarean section, which takes longer to heal, most women are ready to resume prior activity levels by eight weeks post-baby, Peaceman said.

"It's good to get back to the level that you were at prior to pregnancy, so for elite athletes, there's no reason they can't resume training," he said.

Pregnancy causes physical changes that both help and hinder athletic performance. Increased blood flow could be beneficial. But the girth from a swelling belly can change a woman's gait and make her feel off balance. Also, joints and ligaments become more lax, which can raise the risk for injury, Szymanski said.

Some doctors, including the American College of Obstetricians and Gynecologists, discourage most women from bouncy or high-impact workouts during pregnancy and urge them to take it easy at first giving birth because some body changes linger.

The group says some lower-impact activities are generally safe during pregnancy, even for beginners, including swimming and walking. Marathon running isn't listed.

Admirable as it is, Radcliffe's triumph isn't unprecedented. Other elite long-distance runners have won races soon after having babies, including Norway's Ingrid Kristiansen, who won the 1983 Houston marathon within five months of giving birth.

It still seems way out of reach for moms who aren't athletes.

Says Marsha Takeda Morrison, a Los Angeles blogger whose children are 9 and 11, "It's been 3,285 days since I last gave birth and I get winded just walking to the refrigerator."