Q. I know moderate exercise is acceptable during pregnancy, but I feel so tired and out of breath that I haven't been working out. Should I be concerned about my health?

A. It's completely normal to feel tired now that your body is built for two: You have less oxygen available for aerobic exercise, plus you're working hard to support another life. And though not working out isn't exactly dangerous, regular activity -- with your M.D.'s approval -- could make you feel better.

"Exercise can increase your energy level and make labor easier and shorter," says Sheryl Ross, M.D., medical consultant for Birgitta Gallo's Expecting Fitness and an obstetrician/gynecologist in Santa Monica, CA. She recommends that healthy moms-to-be work out for 30 minutes, four or five times a week. If this seems like a tall order, Dr. Ross and Gallo offer this advice:

Pace yourself. Start by adding a walk to your day. If a half hour is too tough, break it up into 10- or 15-minute sessions. But if you're unable to carry on a conversation during your workout or feel fatigued, stop immediately.

Go low. Stick to low-impact activities such as swimming, stationary cycling, and walking -- they're safest.

Give in. "If you're having a bad day, save your energy for tomorrow," says Gallo, a Los Angeles trainer who specializes in pre- and postnatal fitness.

Eat, drink, and be merry. Pregnant women who exercise need 500 extra calories a day, so go for those seconds. And be sure to drink 8 to 12 cups of water a day.

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