There once was a time when pregnant women were expected to take it easy, rest and generally not exert themselves for nine months before taking part in what could possibly be their most grueling physical challenge.

That time is not now.

More often, women are choosing — or being advised by their doctors — to stay active throughout their pregnancies.

"I tell my patients that pregnancy is a great time to exercise," says Deborah Berman, an assistant professor and obstetrician-gynecologist at the University of Michigan. "Health and fitness is important before, during and after a pregnancy. It's not a time to stop exercising and lose your fitness and lose your conditioning."

For some women, working out while expecting is a matter of wanting to bounce back quickly after delivery. Others exercise to remedy pregnancy-induced ailments like back and muscle aches. Most feel that by taking care of themselves, they're also benefiting their soon-to-be-born children.

"I had a great pregnancy experience, and I think I owe it to staying active," says Romina Profeta, a physical therapist from Grosse Pointe Woods, Mich., who gave birth to her first son in 2004.

Jill Rasmussen, health and fitness director at a YMCA in Manitowoc, Wis., says just about any pregnant woman can maintain an exercise program or start one.

"I see no reason a woman should stop exercise," said Rasmussen.

Knowing how to stay active while you're expecting can be tricky. Workouts that are suitable for a nonpregnant person — such as running — can also work during pregnancy, but only up to a point, experts say.

Gentle activities specifically geared toward pregnancy are smart choices for moms-to-be, says Carolyne Anthony, founder and director of the Center for Women's Fitness in Ann Arbor, Mich. She teaches prenatal fitness classes around the world and also trains instructors in pregnancy fitness techniques.

Yoga, water aerobics and walking are popular options.

"This is not the time to be worried about gaining weight or losing your fitness level," Anthony writes in an e-mail from southeast Asia, where she recently conducted training workshops. "It is a time to be gentle with your body and to begin exercising the correct way to help with the birthing of the baby."

Women who are physically active prior to pregnancy can usually keep up a comparable level of activity while pregnant, as long as they are checking in with a doctor and listening to their bodies' cues that they need to ease up, says Berman.

"Most women's bodies will speak to them," says Berman.

CHECK WITH DOCTOR, START SLOWLY

If you are just starting an exercise program as a way of improving your health during your pregnancy, start very slowly and be careful not to overexert yourself. Here are additional tips:

• Consult with your doctor to put together an exercise plan appropriate for you.

• Don't exercise if you have risk factors for preterm labor, vaginal bleeding or premature rupture of membranes.

• Wear comfortable exercise footwear that gives strong ankle and arch support.

• Don't start a new, strenuous workout routine while pregnant.

• Contact sports should be avoided during pregnancy.

• Weight training should emphasize improving tone, especially in the upper body and abdominal area. Avoid lifting weights over your head and using weights that strain the lower back.

• Listen to your body. Dizziness, shortness of breath, headache, chest pain, cramping, contracting and bleeding are signs to slow down, stop, or see your doctor.

• Be aware that the extra weight can cause your center of gravity to shift, making it easier to lose your balance.

• Drink plenty of water before, during and after exercise.

• Avoid exercising in extreme heat. Activities such as water aerobics, yoga, stretching and walking can be gentle on the body.

• Avoid activities that have a high risk of injury or falls.

• Women on bed rest should talk with their doctor about exercise options.

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