Heartburn During Pregnancy: Why It Happens and How to Get Relief

Heartburn during pregnancy is one of those symptoms that sounds manageable until you're experiencing it at 2am with a burning sensation rising from your stomach to your throat, unable to lie flat, unable to find a comfortable position, and facing several more weeks of the same.

It affects the majority of pregnant women to some degree and becomes more common and more intense as pregnancy progresses. For some women it begins in the first trimester. For most it peaks in the third trimester when the physical and hormonal factors driving it are at their strongest.

The good news is that pregnancy heartburn responds well to a combination of dietary, positional, and where needed, pharmacological management. Most women find meaningful relief without needing prescription medication, though safe options are available when self-management isn't sufficient.

Why heartburn happens during pregnancy

Heartburn in pregnancy has two overlapping causes that compound each other across the trimesters.

The hormonal cause. Progesterone, which rises significantly in early pregnancy and remains elevated throughout, relaxes smooth muscle throughout the body. This is necessary for many aspects of pregnancy, including allowing the uterus to grow and preventing premature contractions. However the lower oesophageal sphincter, the valve between the oesophagus and the stomach that normally prevents stomach acid from rising, is also smooth muscle. When progesterone relaxes it, the valve becomes less effective at keeping stomach acid where it belongs. The result is acid reflux and the burning sensation in the chest and throat that characterises heartburn.

The mechanical cause. As your uterus grows, it puts increasing upward pressure on your stomach. This reduces the stomach's capacity, which means it fills faster and empties more slowly. It also physically pushes stomach acid upward toward the weakened valve. In the third trimester, when the uterus is at its largest, this mechanical pressure is at its greatest. Many women who managed heartburn reasonably well in the second trimester find it worsens significantly in the final weeks of pregnancy.

The combination of a relaxed valve and a compressed stomach means that heartburn in the third trimester can be triggered by eating modest amounts of food, lying down after eating, bending over, and sometimes by nothing in particular.

Dietary changes that help

Diet is the most immediately controllable factor in managing pregnancy heartburn, and the changes that help are consistent across most people.

Eat smaller meals more frequently. Three large meals become five or six smaller ones. A full stomach increases the pressure pushing against the weakened valve. Smaller volumes of food mean less pressure at any given time and faster gastric emptying. This single change makes a more consistent difference to heartburn management than almost anything else.

Eat your evening meal earlier and keep it your lightest meal. Lying down within an hour or two of eating is one of the most reliable heartburn triggers in pregnancy. The earlier your evening meal and the smaller it is, the more time your stomach has to empty before you're horizontal. Many women find that eating their main meal at midday rather than in the evening significantly reduces overnight heartburn.

Avoid known trigger foods. Common heartburn triggers include fatty and fried foods, spicy foods, tomato-based foods, citrus, chocolate, coffee, and carbonated drinks. Not all triggers affect all people equally — keeping a rough mental note of which foods consistently precede heartburn allows you to reduce rather than eliminate them rather than overhauling your entire diet.

Avoid eating within two hours of lying down. This applies to naps as well as overnight sleep. If you need a snack close to bedtime, something small and low-acid is less likely to trigger symptoms than a substantial meal. Plain crackers, a small amount of yoghurt, or a banana are generally well tolerated.

Chew food thoroughly and eat slowly. Eating quickly increases air swallowing, which contributes to the bloating and upward pressure that worsens heartburn. Eating slowly and chewing thoroughly reduces this.

Positional changes that help

Elevate the head of your bed. This is one of the most consistently effective interventions for pregnancy heartburn and one of the most underused. Raising the head of the bed by ten to fifteen centimetres uses gravity to keep stomach acid in the stomach overnight. You can achieve this by placing books or purpose-made bed risers under the legs at the head end, or by using a firm wedge under your upper body. Stacking extra pillows under your head achieves less than elevating the whole upper body, as the angle is less effective.

Sleep on your left side where possible. The stomach sits slightly to the left of centre in the abdomen. Lying on the left side keeps the junction between the stomach and oesophagus above the level of stomach acid for most people, which reduces overnight reflux. Right-side sleeping can allow acid to pool at the valve more easily. If heartburn is a specific overnight issue and you're comfortable on either side, left-side preference is worth trying.

Stay upright after eating. Sitting upright or walking gently after meals helps gastric emptying and keeps gravity working in your favour. Lying down or reclining immediately after eating is one of the most reliable ways to provoke heartburn regardless of what you ate.

Wear loose clothing. Tight waistbands and clothing that compresses the abdomen increase the upward pressure on the stomach. Loose, comfortable clothing around the midsection reduces this pressure, particularly after meals.

What you can take safely during pregnancy in Australia

When dietary and positional changes aren't providing adequate relief, several medications are considered safe during pregnancy and are available over the counter at Australian chemists.

Antacids. Products containing calcium carbonate or magnesium hydroxide, including many common brands available at Australian chemists, are generally considered safe during pregnancy and provide rapid relief by neutralising stomach acid. They are most effective when taken after meals and before bed. Antacids containing sodium bicarbonate or large amounts of sodium are generally not recommended during pregnancy as they can cause fluid retention.

Alginates. Products containing alginic acid form a raft on top of stomach contents that acts as a physical barrier against reflux. These are considered safe during pregnancy and are effective for some women where antacids alone are insufficient.

Ranitidine and omeprazole. For more significant heartburn that doesn't respond to antacids, your GP may recommend H2 receptor antagonists or proton pump inhibitors. Some of these have been used in pregnancy for many years and are considered appropriate when benefits outweigh risks. This is a conversation for your GP or health professional rather than self-prescribing.

Do not assume that because something is available over the counter it is automatically safe in pregnancy. Speak with your GP or health professional or a pharmacist before starting any new medication during pregnancy, including antacids, to confirm the specific product is appropriate for your situation.

How heartburn affects sleep and what to do about it

Heartburn and sleep disruption have a particularly circular relationship in pregnancy. Lying down worsens heartburn, which disrupts sleep, which reduces your capacity to manage the next day, which increases stress, which can worsen heartburn.

The combination of elevating the head of the bed, eating your last meal early, and taking an appropriate antacid before bed covers the main overnight management strategies. For women where heartburn is consistently interrupting sleep despite these measures, speaking with a GP about a short course of prescription medication is appropriate. Severe heartburn affecting sleep quality throughout the third trimester is a legitimate medical concern, not something to simply endure.

Side sleeping with the head elevated is the most protective position for overnight heartburn. If side sleeping comfort is also an issue due to hip or back pain, read our third trimester sleep survival guide which covers the full range of third trimester sleep disruption and how to address each cause.

When heartburn warrants medical assessment

Most pregnancy heartburn is benign and manageable. However there are situations where symptoms warrant prompt medical assessment.

Contact your GP or a health professional if heartburn is severe and not responding to over-the-counter antacids, if you are unable to eat or drink adequately due to symptoms, if you experience difficulty swallowing, if you are losing weight, if there is blood in your vomit or in your stools, or if you have severe pain in the upper abdomen rather than the chest area. The last symptom in particular can occasionally indicate a more serious condition including pre-eclampsia and warrants prompt assessment.

Does heartburn mean your baby will have a lot of hair?

This is one of the most persistent pregnancy myths and the answer is: loosely, possibly, but not in the way the folklore implies.

A 2006 study found a statistically significant correlation between heartburn severity during pregnancy and newborn hair quantity, which attracted considerable media attention. The proposed mechanism is that oestrogen, which is associated with fetal hair growth, also relaxes the lower oesophageal sphincter and contributes to heartburn. So the correlation may reflect a shared hormonal driver rather than hair literally causing heartburn.

In practice, most women with severe heartburn have babies with varying amounts of hair, and many women with no heartburn have very hairy babies. It's a fun conversation starter rather than a reliable predictor.