Omeprazole is generally considered safe to use in pregnancy when it’s needed. It’s actually the PPI with the most pregnancy safety data. The largest study, of more than 840,000 births in Denmark, found no significant increase in major birth defects when PPIs were taken in the first trimester, and omeprazole was the most commonly used PPI in that study.

That said, it’s not the first thing doctors reach for. Heartburn in pregnancy is usually treated in steps: lifestyle and diet changes first, then antacids or alginates like Gaviscon, then an H2 blocker like famotidine, with PPIs such as omeprazole reserved for symptoms that don’t respond. A few observational studies have also linked acid-reducing drugs in pregnancy to a slightly higher risk of childhood asthma, although that link may not be caused by the drugs themselves.

If you’re pregnant, trying to conceive or breastfeeding, always check with your doctor, midwife or pharmacist before starting or stopping omeprazole.

Key Takeaways

Heartburn affects 30 to 50% of pregnancies, and up to 80% in some groups, especially in the third trimester.
Omeprazole has more pregnancy safety data than any other PPI, and large studies haven’t shown a clear increase in birth defects.
In a Danish study of 840,968 births, first-trimester PPI use wasn’t significantly linked to major birth defects.
A Korean study of nearly 2.7 million pregnancies found any risk was very small, and disappeared when siblings were compared.
Some studies have found small associations with birth defects or childhood asthma, but these may reflect the underlying conditions rather than the drug.
Doctors usually recommend a step-up approach: lifestyle changes, then antacids or alginates, then famotidine, then a PPI like omeprazole.
Omeprazole is generally considered compatible with breastfeeding, as only small amounts pass into breast milk.
Never stop a prescribed medication during pregnancy without speaking to your doctor or midwife.

Why Is Heartburn So Common in Pregnancy?

Reflux in pregnancy is incredibly common. Reviews estimate heartburn affects 30 to 50% of pregnancies, approaching 80% in some populations, and it usually gets worse as pregnancy goes on [Richter, Alimentary Pharmacology & Therapeutics, 2005].

There are two main reasons:

Hormones. Progesterone relaxes smooth muscle throughout the body, including the lower esophageal sphincter, the valve that normally keeps acid in your stomach. It also slows digestion.
Pressure. As your baby grows, your uterus pushes up against your stomach, forcing its contents upwards, especially after meals and when you lie down.

The good news is that for most people, pregnancy heartburn settles quickly after delivery. I’ve covered the wider picture, including symptoms and practical tips, in my guide to acid reflux and pregnancy.

Is Omeprazole Safe in Pregnancy?

Based on the current evidence, omeprazole appears to be safe to use in pregnancy when the benefits outweigh the risks. Here’s what the research shows.

Birth defects

The most important study comes from Denmark, where researchers linked national registries covering 840,968 live births. Among babies whose mothers took a PPI in the first trimester, 3.2% had a major birth defect, and after adjusting for other factors, this wasn’t a significant increase. There was also no significant increase for individual PPIs, including omeprazole, which was the most widely used [Pasternak & Hviid, The New England Journal of Medicine, 2010].

Interestingly, the same study did find a small increase when PPIs were used in the four weeks before conception, though not with omeprazole specifically. An accompanying editorial called the findings reassuring but not definitive, which is a fair summary of where things stand.

More recent analyses have looked at this question again:

A 2020 meta-analysis found a modest association between PPI use and congenital malformations overall, but said it didn’t have enough power to look at specific drugs or defects [Li et al., Alimentary Pharmacology & Therapeutics, 2020].
A Korean study of nearly 2.7 million pregnancies found a very small increase in risk overall, but when brothers and sisters were compared (to rule out family and genetic factors), there was no association, suggesting PPIs are unlikely to cause birth defects [Choi et al., JAMA Network Open, 2023].

Taken together, the evidence is reassuring. If there is any increased risk, it appears to be very small, and it may be explained by factors other than the medication itself.

Why was omeprazole once rated “category C”?

If you’ve read older information, you may have seen that omeprazole was listed by the US FDA as pregnancy “category C,” while other PPIs were “category B.” This was based on animal studies using very high doses, not on evidence of harm in humans. Ironically, omeprazole now has the most human safety data of any PPI. The FDA has since replaced the letter categories with more detailed descriptions of the evidence.

Childhood asthma

This is the concern that tends to worry parents most. A 2018 meta-analysis of 8 observational studies found that children exposed to acid-reducing drugs in the womb had a higher risk of asthma, with a relative risk of 1.34 for PPIs and 1.57 for H2 blockers [Lai et al., Pediatrics, 2018].

But the authors noted none of the included studies adjusted for the full range of confounding factors. A large UK study that did adjust carefully found no link between prenatal PPI exposure and childhood asthma once maternal health conditions and other medications were taken into account [Cea Soriano et al., Alimentary Pharmacology & Therapeutics, 2016]. One possible explanation is that women who need acid-reducing drugs may differ in other ways, such as having more allergic or respiratory conditions themselves.

So it’s an association worth knowing about, but it hasn’t been shown that omeprazole causes asthma. It’s one more reason to use the lowest effective treatment.

Other pregnancy outcomes

Some observational studies have also reported associations between PPI use in pregnancy and outcomes like preterm birth, but these are difficult to separate from the conditions that lead women to need PPIs in the first place. Overall, major guidelines continue to consider PPIs acceptable when they’re clinically needed.

How Pregnancy Heartburn Is Usually Treated

Doctors and midwives usually take a step-up approach, starting with the safest options and only moving on if symptoms persist [Richter, Alimentary Pharmacology & Therapeutics, 2005]:

Step 1: Lifestyle and diet changes

Eat smaller, more frequent meals rather than three large ones.
Stop eating 2 to 3 hours before bed. More in how long before bed you should stop eating.
Raise the head of your bed or use a wedge pillow. See how to raise the head of your bed.
Sleep on your left side, which is also commonly recommended later in pregnancy.
Avoid common triggers like fatty or fried foods, chocolate, spicy food, citrus, tomatoes, fizzy drinks and caffeine.
Wear loose clothing around your waist.
Stay upright for a while after eating.

A well-structured low-acid diet can make a huge difference here, and it has no effect on your baby. That’s why I’d suggest the Wipeout Diet Plan as a starting point, as it gives you a clear list of gentle, nourishing foods to build meals around.

Step 2: Antacids and alginates

Calcium-based antacids (like Tums) and alginates (like Gaviscon) are usually the first medications recommended in pregnancy, because very little is absorbed into your bloodstream. A recent review of the evidence recommends calcium-containing antacids as the preferred antacid in pregnancy [Altuwaijri, Medicine, 2022].

Alginates, such as Gaviscon Advance, form a protective raft on top of your stomach contents. They’re particularly good after meals and before bed. More in alginates for acid reflux.
Calcium carbonate antacids neutralize acid quickly. See are Tums safe for acid reflux.
Avoid sodium bicarbonate (baking soda) and magnesium trisilicate products in pregnancy, as they can cause fluid and electrolyte problems.
Separate antacids from iron and prenatal vitamins by a couple of hours, as they can reduce absorption.

Step 3: H2 blockers

If antacids and alginates aren’t enough, famotidine is often the next step. It reduces acid production and has a good safety record in pregnancy. My comparison of famotidine vs omeprazole covers how they differ.

Step 4: PPIs like omeprazole

For severe or persistent symptoms, or complications like esophagitis, a PPI may be prescribed. Omeprazole is often chosen because it has the most safety data. Your doctor will usually use the lowest dose that controls your symptoms, often 20mg once a day. For best results, take it 30 to 60 minutes before breakfast, as I explain in my guide to the best time of day to take omeprazole.

Can You Take Over-the-Counter Omeprazole While Pregnant?

Over-the-counter omeprazole packs usually advise checking with a doctor or pharmacist before use if you’re pregnant. Don’t start it on your own. A pharmacist or midwife can help you choose the right step, and they’ll also want to rule out other causes of upper abdominal pain in pregnancy.

This is important because some serious pregnancy conditions, including pre-eclampsia and HELLP syndrome, can cause pain under the ribs that can be mistaken for heartburn. Seek urgent medical advice if your “heartburn” comes with a severe headache, vision problems, sudden swelling of your face, hands or feet, pain under the right ribs, or feeling generally very unwell.

Omeprazole While Trying to Conceive

The Danish study found a small increase in birth defects linked to PPI use in the four weeks before conception, though not with omeprazole specifically, and the reason isn’t clear. If you’re planning a pregnancy and take a PPI regularly, it’s worth talking to your doctor about whether you still need it, whether a lower dose would work, or whether to switch to an alternative. Don’t stop suddenly, as rebound acid can make symptoms worse. My guide to getting off PPIs explains how to taper.

Is Omeprazole Safe While Breastfeeding?

Omeprazole is generally considered compatible with breastfeeding. Only small amounts pass into breast milk, and any omeprazole that does reach your baby is likely to be broken down by stomach acid before it can be absorbed. Famotidine is also commonly used while breastfeeding. As always, check with your doctor, health visitor or pharmacist.

The good news is that most pregnancy reflux improves soon after birth, so many people can step down or stop treatment within weeks.

Conclusion

Omeprazole is generally considered safe in pregnancy when it’s needed, and it has more pregnancy safety data than any other PPI. Large studies, including one of more than 840,000 births, haven’t shown a meaningful increase in birth defects with first-trimester use. Some studies have reported small associations with birth defects or childhood asthma, but these may reflect other factors rather than the drug itself. Omeprazole is also generally considered compatible with breastfeeding.

Even so, most doctors use a step-up approach, starting with diet and lifestyle changes, then antacids and alginates, then famotidine, and reserving omeprazole for symptoms that don’t respond. Always talk to your doctor or midwife before starting, stopping or changing any medication during pregnancy.

Because diet is the safest and often most effective first step, the Wipeout Diet Plan is a great place to start. It was designed first and foremost for LPR, the stubborn throat-based form of reflux, but because it targets the same underlying causes, it works just as well for GERD and the classic heartburn so many people get in pregnancy. It walks you step by step through what to eat, what to avoid and how to time your meals, so you can get relief while relying as little as possible on medication.

If you’d prefer to start with something lighter, the Wipeout Food Reference Guide is the essential companion, listing the foods and drinks that are safe for acid reflux and LPR along with their pH values, so you can check anything at a glance.

Frequently Asked Questions

Is omeprazole safe in pregnancy?

Omeprazole is generally considered safe when it’s needed in pregnancy. Large studies haven’t found a significant increase in birth defects with first-trimester use, and it has the most safety data of any PPI. Doctors usually try lifestyle changes, antacids, alginates and famotidine first.

Can I take omeprazole in the first trimester?

If your doctor feels it’s needed, yes. The largest study, covering 840,968 births, found no significant increase in major birth defects with PPI use in the first trimester. Always discuss it with your doctor or midwife first.

Which is safer in pregnancy, omeprazole or famotidine?

Both are considered acceptable when needed. Famotidine is often tried before a PPI because it’s gentler and has a long safety record. Omeprazole is usually reserved for more severe symptoms, and it has the most pregnancy safety data among the PPIs.

Does omeprazole in pregnancy cause asthma in babies?

Some observational studies have linked acid-reducing drugs in pregnancy with a slightly higher risk of childhood asthma. However, a large UK study that adjusted for maternal health and other medications found no link with PPIs, so it hasn’t been shown that omeprazole causes asthma.

What is the safest heartburn medicine during pregnancy?

Calcium-based antacids and alginates like Gaviscon are usually recommended first, because very little is absorbed into the bloodstream. Avoid sodium bicarbonate and magnesium trisilicate products. Famotidine and then omeprazole are options if these aren’t enough.

Can I take omeprazole while breastfeeding?

Omeprazole is generally considered compatible with breastfeeding, as only small amounts pass into breast milk and are likely broken down in your baby’s stomach. Check with your doctor or pharmacist before taking it.

When should I worry about heartburn in pregnancy?

Seek urgent advice if upper abdominal pain comes with severe headache, vision changes, sudden swelling, pain under the right ribs, vomiting blood or feeling very unwell. These can be signs of serious conditions like pre-eclampsia rather than simple heartburn.

Research & References

[Richter, Alimentary Pharmacology & Therapeutics, 2005] — Review of heartburn management in pregnancy estimating it affects 30 to 50% of pregnancies, and recommending a step-up approach from lifestyle changes to antacids, H2 blockers and then PPIs.
[Pasternak & Hviid, The New England Journal of Medicine, 2010] — Danish registry study of 840,968 live births finding first-trimester PPI exposure was not significantly associated with major birth defects, including for individual PPIs.
[Li et al., Alimentary Pharmacology & Therapeutics, 2020] — Meta-analysis reporting a modest association between maternal PPI use and congenital malformations, with insufficient power to assess specific drugs or defects.
[Choi et al., JAMA Network Open, 2023] — Korean cohort of 2,696,216 pregnancies finding a very small increased risk of major malformations with early-pregnancy PPI use, with no association in sibling-controlled analyses.
[Lai et al., Pediatrics, 2018] — Meta-analysis of 8 observational studies linking prenatal acid-suppressive drug use with higher childhood asthma risk, while noting the studies didn’t adjust for all known confounders.
[Cea Soriano et al., Alimentary Pharmacology & Therapeutics, 2016] — UK cohort study finding no association between prenatal PPI exposure and childhood asthma after adjusting for maternal comorbidities and other medications.
[Altuwaijri, Medicine, 2022] — Evidence-based review of GERD treatment in pregnancy recommending a step-up approach, with calcium-containing antacids as the preferred antacid.

David Gray

12 years living with LPR · Consultant & researcher

Every claim sourced to peer-reviewed research Editorial policy

I've lived with LPR for twelve years — the misdiagnoses, the PPI courses that did nothing, the slow work of figuring out what actually helps. Wipeout Reflux is where I translate the research into plain terms for people stuck in the same place. Every claim here is sourced to peer-reviewed work, and I consult one-to-one with LPR sufferers.

View all articles by David Gray

Is Omeprazole Safe in Pregnancy? What Studies Show