What it is: Once you get your appetite back and are able to keep down your meals, many women are faced with digestive issues such as constipation and gas. Pregnancy causes an increase in the hormone progesterone, which relaxes the smooth muscles throughout your body, including those in your digestive tract, which translates to slower digestion. How it affects exercise: Irregularity may cause pains that make it uncomfortable to exercise, but keeping up with your workouts will actually get things moving (if you know what I mean). If you're embarrassed about gas, choose workouts that are away from people, or with so many people, no one will know it's you. Or go to prenatal exercise classes where you're surrounded by other women with the same issue. It also helps to stay hydrated and eat your fill of fiber-rich fruits, veggies, and whole grains. If you suspect the high iron in your prenatal vitamin is the culprit of your constipation, ask your doc about switching to one that has a lower dose.