Asbeth Gazzo of Springfield, Ill., exercised religiously five days a week for years and planned to keep it up when she became pregnant. Then she found out she was having twins.

"For the first few months everything was fine," says Gazzo. "Then it seemed like I became so unwieldy that I felt wobbly with any of the strength training exercises I tried. My midwife suggested using a birth ball, and it was wonderful. I used it for the remainder of my pregnancy, during my labor and when I first started exercising again after the twins were born. I still use it for shoulder presses."

Exercise balls, also referred to as fitness balls, physical therapy balls, and, in the world of childbirth, "birth balls," are the hottest birth tool around. But their uses go well beyond easing labor. In fact, Ann Douglas, author of The Mother of All Pregnancy Books (Wiley, 2002), says a pregnant woman's first use of a birth ball should not be during labor at all because it takes a bit of practice to master the technique of balancing on the ball. That's good advice because using a birth ball to prepare your body for labor is one of the most effective ways a pregnant woman can exercise.

Before you even think about exercising, the standard disclaimers apply: get your doctor's approval; if it hurts, stop; don't overdo it. After that, the most important thing is choosing the proper ball.

Connie Livingston, a registered nurse, Lamaze certified childbirth educator, doula and administrator of BirthSource.com, notes that a birth ball should be latex free, slow-deflating and weight tested to up to 600 pounds. They aren't very expensive, usually selling for less than $50, so it's a good idea to purchase your own to use throughout pregnancy, during labor and after the baby is born.

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