For Chicago aerobics instructor Julie Jones, it wasn't easy to switch to a less-active lifestyle during her pregnancy. But she soon found the perfect alternative: water aerobics.

"You just naturally crave the water when you're pregnant," Jones says. "Water aerobics gives you a great workout without putting stress on your body. "When you're carrying an extra 20 or 30 pounds, she says, it's nice to take a load off in the pool. In fact, if you weigh 120 pounds, experts say it feels more like 12 pounds in the water.

Jones says doing water aerobics prevented her from getting the swollen knees and ankles. Aqua fitness also keeps your stomach muscles strong and prevents spider veins from appearing on your legs, she says. Exercise also helped ease her morning sickness, balanced her moods and gave her an energy boost. "It's like a natural Prozac," she says.

Dr. Jane Katz, a City University of New York physical education professor, agrees. Studies have shown women who exercise have an easier time in the delivery room, Katz says. They also shed pounds faster after childbirth.

And water aerobics is an ideal form of exercise because expectant mothers can stay cool while they're working out. That's important because women who get overheated while exercising can harm their baby and cause potential birth defects.

Since no two pregnancies are alike, Katz strongly urges everyone to consult their doctor before starting a workout routine. While water aerobics has many benefits, Katz says certain moves aren't safe if you're pregnant. For example, it's a good idea to avoid any type of stomach crunches. Also, bouncing or jumping out of the water can lead to muscle strain and back problems, she says. When in doubt, ask your instructor if it's safe.

"There's a low-impact alternative for every move," Katz says. In her book, Water Fitness During Your Pregnancy, Katz outlines specific routines for different stages of pregnancy. The workouts also incorporate the breathing techniques most women learn during Lamaze classes.

To order the book, call 1-800-747-4457 or visit the website: www.humankinetics.com.