Pregnancy heartburn most commonly starts in the second trimester, though about one in four women experience it in the first trimester. It tends to get progressively worse as pregnancy advances, peaking in the third trimester when more than half of pregnant women are affected. The timing varies from person to person depending on hormonal sensitivity, body size, and the baby’s growth.
Trimester-by-Trimester Breakdown
A large meta-analysis of global data found that heartburn and related reflux symptoms follow a clear upward trend across pregnancy. In the first trimester, about 26% of pregnant women experience symptoms. That number climbs to roughly 33% in the second trimester and reaches nearly 56% in the third. So while heartburn can technically show up at any point, it becomes significantly more common and more intense as pregnancy progresses.
If you’re in the first trimester and already dealing with a burning sensation in your chest or throat, you’re not imagining it. Early-pregnancy heartburn is real, just less common. For most women, though, the second trimester is when it first becomes noticeable, and the third trimester is when it becomes hard to ignore.
Why Pregnancy Causes Heartburn
Two things are happening simultaneously, and they compound each other.
The first is hormonal. Progesterone, which rises sharply during pregnancy to support the uterus, also relaxes smooth muscle throughout your body. That includes the ring of muscle at the top of your stomach (the lower esophageal sphincter) that normally keeps stomach acid from traveling upward. Progesterone triggers the release of nitric oxide inside these muscle cells, which causes them to relax. The result: acid escapes into the esophagus more easily. This mechanism kicks in early, which is why some women get heartburn before they’re even showing.
The second is mechanical. As your baby and uterus grow, they push upward against your stomach. This physical pressure forces stomach contents toward the already-relaxed sphincter. It’s the main reason heartburn intensifies in the second half of pregnancy and often peaks in the final weeks before delivery.
Foods That Make It Worse
Not all trigger foods work the same way. A small group of foods directly relax the esophageal sphincter, making acid reflux more likely regardless of how much you eat. These include peppermint, tomatoes, caffeine, and chocolate. If you’re prone to heartburn, these are the most impactful ones to cut back on.
A wider range of foods don’t cause reflux on their own but irritate the esophagus once it’s already inflamed. Fatty foods, spicy dishes, hot beverages, carbonated drinks, and citrus juices all fall into this category. The distinction matters because you may tolerate these foods fine early in pregnancy but find they become unbearable later, once your esophagus has been dealing with acid exposure for weeks.
What Actually Helps
Current treatment guidelines recommend a step-up approach, starting with the simplest interventions and adding medications only if those don’t work.
Lifestyle changes come first. Eating smaller, more frequent meals reduces the volume of food pressing against your sphincter at any given time. Staying upright for at least two to three hours after eating helps gravity keep acid in your stomach. Elevating the head of your bed (not just stacking pillows, but tilting the mattress or using a wedge) can reduce nighttime symptoms significantly. Sleeping on your left side also keeps the junction between your esophagus and stomach positioned above the level of stomach acid.
If those changes aren’t enough, calcium-based antacids are the preferred first-line medication. They’re considered the safest option during pregnancy, and the calcium itself has a secondary benefit of supporting bone health and potentially reducing preeclampsia risk. If you’re 19 or older, the upper daily limit for calcium during pregnancy is 2,500 mg, so keep an eye on how many tablets you’re taking if you use them frequently.
Avoid antacids that contain bicarbonate, which can cause fluid overload, or magnesium trisilicate, which in high doses has been linked to breathing problems in newborns.
When antacids alone aren’t controlling symptoms, your provider may recommend a stomach-coating medication (sucralfate), which is poorly absorbed into the bloodstream and considered safe. Beyond that, acid-reducing medications like H2 blockers can be combined with antacids. Stronger acid-suppressing drugs (proton pump inhibitors) are reserved for severe cases that don’t respond to anything else.
When Heartburn Might Signal Something Else
Ordinary pregnancy heartburn is a burning sensation in the chest or throat, often after eating or when lying down. It’s uncomfortable but predictable. What’s worth paying attention to is pain that feels different from typical heartburn, specifically pain concentrated in the upper right side of your abdomen or just below your breastbone, especially if it comes with a new headache that won’t go away, visual changes (blurriness, seeing spots), or nausea and vomiting that seem unrelated to food.
This combination of symptoms can indicate preeclampsia or a related liver condition called HELLP syndrome, both of which require immediate medical evaluation. The upper abdominal pain in these conditions is caused by liver swelling, not acid reflux, but it’s easy to dismiss as “just heartburn” if you’re used to dealing with reflux. The distinguishing features are the location (right side or center, not the chest), the severity, and the accompanying symptoms like headache or vision changes.
Does It Go Away After Delivery?
For most women, heartburn resolves after giving birth as progesterone levels drop and the uterus shrinks. About 80% of women find their symptoms disappear entirely. The remaining 20% continue to experience some degree of reflux after delivery, which may indicate a preexisting tendency toward acid reflux that pregnancy unmasked rather than caused. If your symptoms persist beyond a few weeks postpartum, it’s worth discussing with your provider rather than assuming it will eventually fade on its own.