Constipation is a common problem for pregnant women. During pregnancy, high levels of progesterone slow the movement of food through your digestive track, and as your bump grows, the pressure from your uterus onto your rectum only makes things worse. And yes, it can be made worse by the iron in your prenatal vitamins.
If you suspect the iron levels in your vitamin are to blame, check the label—you probably don't need more than 30 milligrams of iron a day, unless you're anemic. (If your prenatal has more, ask your doctor if you can switch.) To help the problem, make sure you're getting at least eight cups (64 ounces) of water each day (juice and decaf tea are good options too). Also, add more fiber-rich foods to your diet, such as whole grains, beans, veggies and fruit. But as you increase your fiber, be sure to increase your fluids—otherwise, your tummy will just feel worse! Make an effort to stay active—the more you move, the more your bowels will too. If you've tried all of these things and still aren't regular, talk to your doctor.