That burning feeling in your stomach during pregnancy is almost certainly acid reflux, and it’s one of the most common pregnancy symptoms. About 26% of pregnant women experience it in the first trimester, rising to 33% in the second and peaking at nearly 56% in the third. Two things drive it: hormonal changes that loosen the valve between your stomach and esophagus, and the physical pressure of your growing uterus pushing your stomach upward.
What Causes the Burning
The main culprit is progesterone, a hormone that rises steadily throughout pregnancy. Progesterone relaxes smooth muscle throughout your body, which is essential for keeping your uterus from contracting too early. But it also relaxes the muscular valve at the top of your stomach, the one that normally keeps acid from splashing up into your esophagus. As progesterone climbs, that valve gets progressively weaker, and acid escapes more easily. Researchers have documented that the valve’s pressure drops steadily as pregnancy advances and returns to normal soon after delivery.
The second factor is physical. By the third trimester, your uterus has grown to roughly the size of a watermelon and extends up near your rib cage. Your stomach, liver, and intestines all shift upward to make room. This compression squeezes your stomach into a smaller space, which increases pressure on its contents and makes reflux worse. It’s also why you may notice you can’t eat as much in one sitting late in pregnancy.
These two forces, hormonal and mechanical, build on each other as pregnancy progresses. That’s why the burning tends to get worse over time rather than better.
How to Tell It Apart From Something Serious
Ordinary pregnancy heartburn produces a burning sensation behind your breastbone or in your upper stomach, often after eating or when lying down. It comes and goes, and it responds to antacids or position changes.
What deserves immediate attention is different. Severe pain in your right upper abdomen, especially after 20 weeks, can signal conditions like preeclampsia or a related liver complication called HELLP syndrome. Between 50% and 90% of women with these conditions report right upper quadrant or upper stomach pain, often accompanied by nausea, vomiting, headache, or visual changes. The CDC lists severe belly pain that doesn’t go away, starts suddenly, or gets progressively worse as an urgent maternal warning sign. If your burning is intense, persistent, located more to your right side, or paired with headache, swelling, or changes in your vision, contact your provider right away rather than assuming it’s heartburn.
Lifestyle Changes That Help
Before reaching for medication, a few adjustments can make a real difference. Eating smaller, more frequent meals reduces the volume of food pressing against that weakened valve. Avoiding food for two to three hours before lying down gives your stomach time to empty. Elevating the head of your bed by a few inches (using a wedge pillow or blocks under the bed frame, not just extra pillows) keeps gravity working in your favor overnight.
Sleep position matters more than most people realize. Lying on your left side positions your esophagus above the opening of your stomach, so acid is less likely to flow upward. Lying on your right side does the opposite: it places the esophagus below that opening, making reflux worse and slowing the time it takes for acid to clear. A systematic review confirmed that left-side sleeping significantly improves reflux symptoms.
Chewing gum after meals can also help by stimulating saliva production, which naturally neutralizes acid. Common dietary triggers worth avoiding include spicy or fatty foods, citrus, chocolate, and caffeine, though your personal triggers may vary.
Medications That Are Safe During Pregnancy
When lifestyle changes aren’t enough, over-the-counter antacids containing aluminum, calcium, or magnesium are considered first-line treatment. These have been studied extensively in pregnancy with no evidence of harm to the baby. Calcium-based antacids (like Tums) are a popular choice because they also contribute to your daily calcium needs. If you’re 19 or older, the upper limit for calcium during pregnancy is 2,500 mg per day. Going above that, particularly with prolonged high doses, has been linked to a rare condition called milk-alkali syndrome. Check the label for the “elemental calcium” amount to keep track.
Two types of antacids to avoid: those containing bicarbonate (risk of fluid overload) and high doses of magnesium trisilicate (associated with kidney and breathing problems in the fetus).
If antacids aren’t cutting it, acid-reducing medications are the next step. A large meta-analysis of nearly 2,400 pregnant women who took acid reducers in the first trimester found no significant increase in birth defects, miscarriage, or preterm delivery. Stronger acid-suppressing medications have similar safety data from a study of over 1,500 first-trimester exposures. Your provider can help you decide which option fits your symptoms.
When It Gets Worse by Trimester
In the first trimester, about one in four women experience reflux symptoms. At this stage, hormonal changes are the primary driver since the uterus is still small. Nausea from morning sickness can overlap with and worsen the burning sensation, making it hard to tell one from the other.
By the second trimester, prevalence rises to about one in three. The uterus is growing but hasn’t yet caused major organ displacement, so hormone levels remain the bigger factor. Many women notice symptoms creeping in after meals or at bedtime.
The third trimester is the peak, with more than half of pregnant women affected. Your stomach is now physically compressed and pushed upward, and progesterone levels are at their highest. Eating large meals becomes uncomfortable, and nighttime reflux can disrupt sleep significantly.
What Happens After Delivery
For most women, the burning resolves after giving birth. Progesterone drops quickly, the valve regains its normal tone, and the uterus shrinks, allowing your stomach to return to its usual position. However, pregnancy may leave a lasting mark for some women. One longitudinal study found that 4.7% of women who had reflux during pregnancy still experienced frequent symptoms a year after delivery, compared to just 1.3% of women who were never pregnant. If your symptoms persist well beyond delivery, it’s worth mentioning to your provider since you may benefit from continued treatment.