ABSTRACT
Gastrointestinal Effects A number of characteristic changes are associated with the gastrointestinal system. Perhaps the best known change, "morning sickness," is of unknown origin and generally confined to the first trimester, but nausea may persist throughout pregnancy. We know the causes of some other changes. For example, constipation results when hormones decrease the motility of the bowel (progesterone relaxes the intestinal musculature) and the enlarging uterus exerts pressure on the bowels. Heartburn (a burning sensation in the chest due to acid reflux into the esophagus) is a secondary effect of relaxation of the cardiac sphincter muscle. The pregnant woman may also be predisposed to gallstone formation because of delayed emptying of the gallbladder.
