Myth: If you are very athletic, you need to greatly dial down your exercise intensity.
Reality: Though nobody recommends gut-busting sprints for pregnant women, you can maintain your program as long as your body and your doctor give you the OK. “If there are no complications, women can continue to exercise at a higher level, but we recommend closer medical supervision,” Artal says.
Early in pregnancy, elevating your core body temperature may be damaging to the fetus, so stay hydrated, don’t exercise outdoors in the heat of the day and avoid huffing and puffing so hard that you can’t talk.
Decades ago, the American College of Obstetricians and Gynecologists recommended a ceiling of 140 heartbeats per minute for pregnant women, but the guideline was later withdrawn because heart rate differs so much from one woman to the next. “I tell everyone to forget about heart rate,” says Artal. Just make sure you can talk comfortably. Be flexible. Back off on the days when you’re just not feeling energetic, Haley advises, “and take advantage of those days when you feel like a rock star.”
Myth: Running is unsafe during pregnancy.
Reality: You can’t “shake your baby loose”; she’s plenty safe swimming around in amniotic fluid while you jog at the park. “As long as there are no changes in your joints and ligaments, you can continue running,” Artal says.
Some runners are able to keep going many months into their pregnancies, but eventually even Olympic champions are forced by discomfort to switch to lower-impact activities such as walking, water workouts or the elliptical trainer. “It’s just a matter of nature,” Artal says.
Myth: You shouldn’t work your abs.
Reality: True, doing crunches (or other exercises) on your back is a no-no after the first trimester: Your growing uterus can compress the vena cava, the major vessel that returns blood to your heart, potentially reducing blood flow and making you feel dizzy or nauseated. Artal says only about 10 percent of women are susceptible to this dizziness, but why find out if you’re one of them when there plenty of ways to work your entire core while standing or kneeling?
O’Connor’s study included an ab exercise performed while standing: The women exhaled and then drew in their navel toward their spine “as if they were trying to button up pants that were too tight in the waist,” he says.
Haley performed the plank move, a very effective core exercise, until the day she gave birth to her son. “During those last two hours of pushing,” she says, “I was really grateful I had trained my core.”