Constipation is a common problem during pregnancy. One of the reasons is the hormone progesterone, which slows the movement of food through your digestive tract. And the problem may be compounded later in pregnancy by the pressure of your growing uterus on your rectum. Iron supplements can make constipation worse.
Constipation is usually not serious, though occasionally it can be a symptom of another problem. If you have severe constipation that's accompanied by abdominal pain, alternates with diarrhea, or you pass mucus or blood, call your doctor immediately. Straining during a bowel movement or passing a hard stool can lead to or worsen hemorrhoids, swollen veins in the rectal area. Hemorrhoids can be extremely uncomfortable, though they rarely cause serious problems and in most cases they go away fairly soon after your baby is born.
Stool softeners (like Colace®) and mild laxatives like Milk of Magnesia (we call it M.O.M. in the hospital!) are safe to use during pregnancy. M.O.M. can also be used for heartburn. It is always best to avoid stimulant laxatives (like Dulcolax®, Ex-lax® and Correctol®) unless directed by your practitioner. If you are not sure about a laxative's safety, be sure to ask your practitioner.