On the outside you are glowing from impending motherhood — but on the inside, you are burning from heartburn.

Acid reflux is common during pregnancy, said Dr. Anish Sheth, a gastroenterologist and assistant professor of medicine at Yale University.

“Elevated progestin hormones cause the pressure of the sphincter to go down,” Sheth said. “And the increased pressure of the growing uterus predisposes the woman to acid reflux.”

The good news, Sheth said, is once the baby is born, the symptoms of acid reflux are likely to disappear.

So how do you treat acid reflux during pregnancy?

The safest medicines are H2 receptor blockers, Sheth said, which are sold over-the-counter. These medicines include Pepcid AC and Zantac.

H2 receptors work by shutting off the production of acid in the stomach and are effective in cases of mild reflux.

The effects of more potent drugs like Nexium or Protonix (proton pump inhibitors, or PPIs) have not yet been studied on pregnant women.

Added bonuses of H2 receptors: They are relatively inexpensive and provide longer-lasting relief than antacids.

However, they do not take effect as quickly, so Sheth suggests women take them a half-hour before meals or at bedtime.

Sheth said it is OK to take antacids like Rolaids, Tums and Maalox, but anything with magnesium in it should be avoided in the third trimester because it can cause premature labor. He said pregnant women should never take oral suspension medicines like Pepto Bismol.

If you prefer not to take any kind of medicine during pregnancy, there are some natural ways to relieve heartburn.

One popular method is to eat licorice, because it is flavored with anise, which aids in digestion.

Another popular method — though doctors don’t know where it originated, and there is little evidence to back up the claim — is to drink apple cider vinegar.

However, when it comes to pregnancy and acid reflux, “it comes down to lifestyle,” Sheth said. “Stay upright for several hours after eating and avoid triggers like caffeine and chocolate. For the majority of patients, that will control it.”