Jenny Larsen knows all about listening to your body. For more than a decade, she's been a fitness trainer, teaching men and women kickboxing, yoga, spinning, sports conditioning, step aerobics and more. She's taught kids and adults dance, including thump, Latin and hip hop.

She knows all about listening to your body, and hers has quite a story unfolding. She's pregnant, her baby girl due in October.

Larsen is slowing down a little but not much. She doesn't lie on her back during workouts because it could reduce the baby's blood supply. Ditto lying on her stomach, for obvious reasons. She's less apt to do high jumping. She's doing her "core work" at about half-intensity. She's drinking a lot more water. But when her energy's down, she doesn't stop, although she does take the routine down a notch.

"I'm definitely more tired in pregnancy. I try to exercise before I'm too tired. I hit moments when I can't imagine teaching," says the Jewish Community Center fitness instructor, "but I feel so much better after."

Women are naturally more attuned to their bodies during pregnancy, because so many interesting things are happening. The advice Larsen offers is simple: Listen to it. You know when something doesn't feel right and you're pushing too hard. Slow it down, she said. But don't stop moving.

The reasons are simple. If you know what you're doing, you can strengthen the muscles and ligaments supporting the baby's weight and lessen the potential for pain. You can overcome the sometimes crushing fatigue that may come with pregnancy. You can keep your metabolism going strong for later weight loss of baby-induced fat. You can feel invigorated instead of drained at a time when baby's going to need you to be on your game.

Between her pregnancies — daughter Lily will be 4 in September — she's been working on her lower belly, inner thighs and hip girdle. She's been doing balance and strength training, including the abdominal muscles she'll need to deliver the baby.

The American Academy of Family Physicians advocates exercise and activity but cautions that each pregnant woman should check with her doctor to make sure it's safe.

The American College of Obstetricians and Gynecologists says certain conditions, including pregnancy-induced high blood pressure or preterm labor are among the contraindications to exercise.

Exercise doesn't benefit the baby, but it "might help you feel better and maintain your weight," it says.

Assuming there's no reason exercise would be harmful for the mother-to-be or baby, the family practitioner organization suggests starting out small, at a level that doesn't cause pain, shortness of breath or excessive tiredness.