Although heartburn is a common and relatively harmless ailment, many women do not experience heartburn until pregnancy. Though it is not serious, heartburn can cause a great deal of discomfort. Heartburn is a burning sensation, usually in the upper chest and the base of the throat. Although it is difficult to prevent heartburn during pregnancy, understanding the causes of heartburn during pregnancy can make it easier to cope.Hormonal changesThe primary reason for increases in heartburn during pregnancy is the increase in the hormone progesterone, which relaxes the smooth muscle tissue in the body, including the valve in the esophagus that keeps food from coming back up the throat and the smooth tissue of the intestine, which slows down digestion. Given the weakness of the esophageal valve and the slowness of digestion, this means that pregnant women are more likely to suffer from acid reflux (stomach acid coming back up the esophagus), which is also known as heartburn.Certain foodsWhile women cannot really prevent the hormonal changes that increase the likelihood of heartburn, they can avoid certain foods that are likely to trigger heartburn, which can decrease the chances of experiencing serious heartburn during pregnancy. Citrus foods can increase heartburn, as can alcohol, fatty foods, the extra acid in coffee and the gas in sodas. In addition, chocolate can irritate the stomach, so women should try to keep chocolate eating to only special occasions. They should also try to avoid large meals.Women should try to plan several small, low-fat meals a day, and avoid carbonated drinks during pregnancy. Although women cannot avoid that painful increase in heartburn during pregnancy, there are some things that they can do to understand why heartburn is a new problem and decrease the likelihood of experiencing serious heartburn.