Heartburn occurs when digested food from your stomach, which contains acid, is pushed up toward your esophagus. This causes a burning sensation behind your breastbone or a burning sensation that starts in your stomach and seems to rise up. You may also have a sour taste in your mouth or a feeling that vomit is rising in your throat.
Normally, food moves down a pipe (called the esophagus) between your mouth and your stomach. When you're not eating, a circular valve around the bottom of your esophagus closes off the connection between your esophagus and your stomach. This valve keeps the acids in your stomach from rising up.
When you swallow, the valve relaxes to allow food and liquid to flow through. If the valve relaxes when you're not eating, the acids from your stomach can flow back up into your esophagus, irritating it and causing a burning sensation.
Several things can cause the valve to relax more easily, such as:
- Greasy or fatty foods
- Chocolate or drinks containing caffeine
- Onions, garlic or spicy foods
- Certain medications
- Eating a very large meal
- Lying down after eating
During pregnancy, hormones relax the muscles in your digestive tract, including the valve in the esophagus. This allows stomach acids to more easily seep back up the esophagus, especially when you're lying down. Heartburn can be worse in the second and third trimesters, when your growing uterus presses on your stomach. This sometimes pushes food back up into the esophagus.
Pregnancy hormones also slow down:
- muscles that push food from your esophagus into your stomach
- muscles that contract to digest food in your stomach, which slows down your digestion
These changes can also lead to indigestion, which can make you feel very full, bloated or gassy.