Heartburn During Pregnancy: Why It Happens and What Actually Helps

You eat a perfectly reasonable dinner, lie down, and within twenty minutes there is a hot line running from your stomach up to your throat. Sitting up helps a little. Milk helps a little. Mostly you lie there doing math on how many weeks are left.

Heartburn during pregnancy is one of the most common complaints there is, and also one of the most fixable — not with a single miracle remedy, but with a handful of small, boring changes that stack up. Here is what the medical sources actually say about why it happens, what helps, what to ask your provider about, and the short list of symptoms that mean stop reading and call.

01What pregnancy heartburn actually feels like

Heartburn has nothing to do with your heart. MedlinePlus, the NIH's consumer health library, describes it as "a painful burning feeling just below or behind the breastbone." The pain "often rises in your chest from your stomach" and "may also spread to your neck or throat."

The mechanics are simple. There is a band of muscle at the lower end of your esophagus — the tube from your throat to your stomach — that normally closes off once food has gone down. When it does not close properly, MedlinePlus explains, "food or stomach acid can back up (reflux) into the esophagus." Stomach acid belongs in a stomach lined to handle it. The esophagus is not, so you feel it burn.

And it is extremely common when you are pregnant. The Cleveland Clinic notes that "researchers estimate that anywhere from 30% to 80% of pregnant women experience heartburn." That is a wide range, which tells you something honest: nobody has pinned the number down precisely, but on any reading, a lot of pregnant people are up at night with this.

02Why pregnancy causes it

MedlinePlus puts it bluntly in its list of common pregnancy symptoms: "Pregnancy and many medicines can bring on heartburn or make it worse." There are three separate things going on at once, and the Cleveland Clinic separates them out.

• Digestion slows down. "While you are pregnant, food stays in your stomach and bowels longer," MedlinePlus explains — which is exactly what produces the acid backing up. The Cleveland Clinic says the same thing from the other direction: pregnancy hormones "slow your digestive system. Food moves more slowly, increasing the likelihood of bloating, heartburn and constipation."
• The valve at the bottom of the esophagus gets loose. Per the Cleveland Clinic, "the hormone progesterone can cause your lower esophageal sphincter (LES) to relax" — and when it relaxes too much, "it doesn't seal to prevent the backflow of stomach acid." Your body is relaxing smooth muscle all over for good reasons; this is the unwelcome side effect.
• There is a baby where your stomach used to be. "As the fetus grows, your uterus gets bigger," the Cleveland Clinic notes. "It can crowd your stomach, causing stomach acid to flow upward, into your esophagus." This is plain physics, and it is why heartburn often gets worse rather than better as you go.

None of which is your fault, and none of which means you ate the wrong thing. You may well have eaten a trigger food, and we will get to those — but the underlying setup was already in place.

03When does pregnancy heartburn start?

There is no fixed week. The Cleveland Clinic says heartburn can occur anytime during pregnancy but is "more common in the third trimester, when your uterus is the largest and places the most pressure on your stomach." So if you are 30 weeks in and this just started, that fits the pattern exactly. If it started at 10 weeks, that fits too — the hormonal slowdown does not wait for a bump.

Here is something we will not tell you: that it reliably disappears the moment you give birth. It is a claim you will see repeated everywhere, and none of the sources we fetched for this article actually states it, so we are not going to present it as fact. What the sources do say is that the third-trimester version is driven by pressure from the largest your uterus will get. Ask your own provider what to expect afterward — they can tell you about your pregnancy rather than about pregnancy in general.

If you are heading into the last stretch, our third trimester checklist covers what is worth getting done while you still have the energy — and a few things worth moving earlier than most lists put them.

04What actually helps

Almost everything on this list is about when and how much you eat rather than what — which is good news, because the when and how much are under your control on a day when nothing else is.

One more, and it belongs to the person who is not pregnant: if smoking happens in your house, MedlinePlus lists stopping smoking or using tobacco among its home-care steps for heartburn. That one is worth doing for about fifteen other reasons too.

05Night heartburn: the one that wakes you up

Lying flat removes the only thing that was keeping acid down, which is gravity. The fix is to put gravity back.

MedlinePlus is specific: "sleep with your head raised about 6 inches." The Cleveland Clinic gives the same advice as elevating the head of your bed. Note that this means raising the whole upper half of you — stacking pillows under your head alone tends to bend you at the neck and do very little for your stomach. A wedge pillow, or something solid under the legs at the head of the bed, works better than a pillow tower.

Our guide to pregnancy sleep positions covers how to stack this with the other things you are trying to get right overnight, because by the third trimester there are several and they do not always agree with each other.

06Antacids and medicine: what to ask about

This is the part where we are going to be more careful than most articles, because the right answer genuinely depends on you, your pregnancy, and anything else you take.

The Cleveland Clinic's instruction is direct: "talk to your healthcare provider before taking antacids or any other medicine for heartburn," and it notes that the risk of harm to a fetus "tends to be most significant during the first trimester." MedlinePlus says the same from the other side: "if you continue to have heartburn, talk to your provider about medicines that can help." So the move is not to guess in a drugstore aisle — it is to arrive at your appointment with the question already formed.

How antacids work, and how to use them

Antacids are the chewable tablets and liquids that "work by neutralizing the stomach acid that causes heartburn," per MedlinePlus. Timing matters more than people realize: "take antacids about 1 hour after eating or when you have heartburn. If you are taking them for symptoms at night, do not take them with food."

The ingredient also changes the side effects, which is useful to know when you are already dealing with pregnancy digestion. MedlinePlus notes that brands with magnesium "may cause diarrhea," while brands with calcium or aluminum "may cause constipation" — and rarely, calcium-based ones "may cause kidney stones or other problems." It also warns that large amounts of aluminum-containing antacids can put you at risk for calcium loss and weaker bones. And one line worth taking seriously: "contact your provider if you need to use antacids on most days." Daily reliance is a signal, not a solution.

If antacids are not enough

There are stronger acid-reducing medicines, and your provider is the one to pick among them. For context on one of the common ones, the MotherToBaby fact sheet on famotidine — MotherToBaby is the service run by the Organization of Teratology Information Specialists that answers exactly these questions — notes that famotidine "has been used to treat acid reflux (heartburn) or peptic ulcer disease" and that "studies on the use of famotidine in pregnancy do not report an increased chance of birth defects." It is also candid about what is not known: "studies have not been done to see if famotidine can increase the chance of miscarriage." For later on, it adds that "taking famotidine while breastfeeding is not expected to cause problems in children who are nursing."

That fact sheet ends where this section does: "it is important to talk with your healthcare providers before making any changes to how you take your medication." Bring the actual bottle or a photo of the label to your appointment — it saves a round of phone tag.

07When heartburn is a reason to call

Most pregnancy heartburn is miserable and harmless. A short list of symptoms is neither, and it is worth knowing them cold so you are not deciding at 2 a.m. whether this counts.

MedlinePlus says to seek urgent care if you "vomit material that is bloody or looks like coffee grounds," or if you have "a squeezing, crushing, or pressure in your chest." The Cleveland Clinic adds to the call-your-provider list: heartburn that persists despite lifestyle changes, heartburn that wakes you at night, trouble swallowing, spitting up blood, black stool, and losing weight. MedlinePlus also flags heartburn that "does not go away after a few weeks of self-care."

08Small changes, in the right order

If you only do three things: shrink the meals, stop eating three to four hours before bed, and raise the head of the bed about six inches. Those are the ones with the clearest backing and the lowest cost, and together they handle the night-time version — which is the version that actually wears people down.

The rest of the third trimester has the same shape as this: a long list of small things, and no obvious order to do them in. That is the problem we built this site to solve. Enter your due date and you will get a free, personalized week-by-week plan, with the heavy tasks front-loaded into the middle of pregnancy so the last stretch stays light — because by then, lying down flat is hard enough.

Questions parents actually ask

Newborn Weeks is planning help, not medical advice — always follow your own doctor, midwife, or pediatrician.