Approximately 50 percent of pregnant women will experience heartburn (most common during the second and third trimester.) The reason: As a woman's level of progesterone increases during pregnancy, her lower esophageal sphincter relaxes. This allows food and acid to reflux back into the esophagus, thus creating the feeling of heartburn or indigestion. And with the uterus expanding, additional pressure is put on the abdomen, which is a probable cause of heartburn as well.

With help from the National Heartburn Alliance recommends, here's a guide to preventing heartburn during pregnancy.

Lifestyle. There are a number of small changes you can make in your daily life during pregnancy that will go a long way toward minimizing your heartburn. They include:

  • Eating small, infrequent meals to avoid overloading your stomach
  • Avoiding trigger foods (fats, chocolates, citruses, caffeinated, and carbonated drinks) or trying low-acid options
  • Avoiding meals 2 to 3 hours before bedtime
  • Avoiding cigarettes and alcohol (abstaining from these behaviors is also especially important for the health of the developing fetus)
  • Using dairy products to neutralize gastric acidity
  • Chewing gum after meals (EXCEPT mint and spearmint) to neutralize gastric acidity
  • Wearing loose-fitting pregnancy clothes to decrease pressure on the stomach
  • Elevating the head of your bed 4 to 6 inches

Medication. Though most find relief through lifestyle changes, you can rely on three over-the-counter medications, which are considered the safest during pregnancy.

1. Antacids. Those containing aluminum, calcium, and magnesium are generally safe. (Examples include Tums®, Maalox®, and Mylanta®.) However, there are some important things to know:

  • Calcium is often preferred, but only 1,000 to 1,300 milligrams per day, with an upper limit of 2,500 milligrams per day (which you may receive from other foods and vitamins)
  • Some experts recommend avoid magnesium in the third trimester, as it can interfere with uterine contractions during labor
  • Maalox® Total Stomach Relief should be avoided because it contains bismuth subsalicylate
  • Products containing sodium bicarbonate (like Alka-Seltzer® Heartburn Relief) should be avoided because they may increase fluid retention

2. H2-receptor antagonists. These are safe and approved for use during pregnancy by the Food and Drug Administration (FDA). However, some authorities suggest not using cimetidine (Tagamet HB) because of possible hormone interferences. Examples include Tagamet, Zantac, and Pepcid®.

3. Proton pump inhibitors. These should only be used if you have intractable symptoms and have failed with H2-receptor antagonists. However, they should be avoided during the third trimester. Examples include Prilosec®, Prevacid®, and Protonix®.