Is Esomeprazole Safe in Pregnancy? What Studies Show

Esomeprazole is generally considered one of the safer proton pump inhibitors (PPIs) to use during pregnancy, though “safe” comes with important caveats. It was classified as FDA pregnancy category B before that system was retired in 2015, meaning animal studies showed no fetal harm and no well-controlled human trials raised red flags. Large population studies have since filled in more of the picture, and while the overall risk of birth defects does not appear to be meaningfully elevated, a handful of signals in recent research deserve a closer look.

What Large Studies Say About Birth Defects

The biggest worry for anyone taking a medication in early pregnancy is whether it could cause birth defects. A major Danish study published in the New England Journal of Medicine tracked over 840,000 live births and found that about 3.2% of infants exposed to PPIs during the first trimester had a major birth defect. After adjusting for other factors, PPI exposure did not significantly increase the odds of malformations compared to unexposed pregnancies.¹ That 3.2% rate is close to the background rate of birth defects in the general population, which typically hovers around 3%.

A more recent analysis published in JAMA Network Open, however, did find a small wrinkle for esomeprazole specifically. When researchers looked at individual PPIs, esomeprazole was the only one linked to a statistically significant, though small, increase in major congenital malformations, with a relative risk of about 1.10.² That translates to a very modest bump in absolute risk. Researchers have cautioned against reading too much into this finding because when you test multiple drugs individually, some will cross the statistical threshold by chance alone. Still, it is worth noting that the signal appeared for esomeprazole and not for other PPIs in that particular dataset.

How Esomeprazole Behaves in a Pregnant Body

Pregnancy changes how your body processes many drugs, and esomeprazole is no exception. A pharmacokinetic study in women with preterm preeclampsia found that esomeprazole clearance dropped by roughly 42% compared to non-pregnant individuals. The reason is that pregnancy itself partially inhibits the liver enzyme CYP2C19, which is the main pathway for breaking down esomeprazole.³ In practical terms, a pregnant person’s body clears the drug more slowly, so blood levels tend to run higher on the same dose. Interestingly, the usual “autoinhibition” effect (where esomeprazole suppresses its own metabolism with repeated dosing) is less dramatic during pregnancy because CYP2C19 is already partially inhibited by the pregnancy itself.

Esomeprazole does cross the placenta. A case report measuring drug levels in a woman taking esomeprazole found that the concentration in cord blood was about 40% of the level in her own serum.⁴ That means a substantial fraction of the drug reaches the fetus, even though levels are lower than what circulates in the mother. This is not unusual for medications in this class, but it underscores why researchers keep looking at downstream outcomes in the baby.

Pregnancy Complications Beyond Birth Defects

Birth defects grab the most attention, but PPI use during pregnancy has also been linked to a handful of other complications. A large Swedish cohort study found that women who used PPIs during pregnancy had modestly higher odds of preeclampsia, gestational diabetes, preterm birth, and having a baby that was small for gestational age.⁵ The odds ratios ranged from about 1.19 for preeclampsia to 1.29 for gestational diabetes, suggesting the associations are real but not large.

A meta-analysis focused specifically on preeclampsia pulled together multiple studies and found a pooled relative risk of about 1.27 for women who used PPIs at any point during pregnancy. But in absolute terms, the increase amounted to roughly 2 extra cases per 1,000 pregnancies.⁶ Small absolute numbers like this are important context: a relative risk increase can sound alarming, but when the baseline rate is low, the actual number of additional affected people is tiny.

The trickiest part of interpreting these findings is confounding. Women who need PPIs during pregnancy often have more severe reflux, higher BMI, or other conditions that independently raise the risk of complications like preeclampsia and gestational diabetes. Researchers try to adjust for those factors, but it is nearly impossible to eliminate all of them in observational studies. The honest reading of the evidence is that PPIs are associated with these complications in the data, but we cannot say for certain that the drugs themselves cause them.

The Preeclampsia Treatment Question

In an interesting twist, esomeprazole has actually been tested as a potential treatment for preeclampsia, not just studied as a possible contributor. Laboratory work suggested that PPIs could reduce some of the molecules involved in the blood vessel damage that characterizes preeclampsia. A population-based study from nearly 158,000 women found something intriguing: while PPI use during pregnancy overall was associated with a slightly higher risk of preeclampsia at term, using PPIs after 28 weeks of gestation was associated with a reduced risk of preterm preeclampsia and early preeclampsia.⁷

That finding prompted a randomized controlled trial in which women diagnosed with preterm preeclampsia were given either 40 mg of esomeprazole daily or a placebo. Unfortunately, the trial found no significant difference: the esomeprazole group delivered a median of about 11.4 days after randomization compared to 8.3 days in the placebo group, a gap that was not statistically meaningful. There were also no differences in other maternal or neonatal outcomes.⁸ So as of now, esomeprazole is not a proven treatment for preeclampsia, despite the theoretical rationale. The research is ongoing, but clinicians should not prescribe it with that goal in mind.

Infection Risk During Pregnancy

PPIs suppress stomach acid, which serves as one of your body’s defenses against swallowed pathogens. Outside of pregnancy, long-term PPI use is already linked to higher rates of certain infections. A large nationwide cohort study of over 1.5 million pregnancies looked at whether PPI use during pregnancy raised infection risk and found a clear association. Women who used PPIs had a roughly 26% higher adjusted risk of developing any infection during pregnancy compared to those who did not use them.⁹

The risk was not uniform across infection types. Gastrointestinal infections showed the highest relative increase at about double the risk, which makes intuitive sense given that stomach acid normally kills many food-borne pathogens. Viral infections were also roughly twice as common among PPI users, while bacterial infections were about 43% more frequent. Even moderate-to-severe infections and infection-related pregnancy complications ticked upward. These numbers are large enough to take seriously, though the same confounding issues apply: women using PPIs may differ from non-users in ways that independently raise infection risk.

Childhood Asthma in Exposed Children

One of the more unsettling signals involves longer-term outcomes for children born to mothers who used PPIs. A population-based Danish cohort study found that children whose mothers took PPIs during pregnancy had a 41% higher rate of developing asthma compared to unexposed children.¹⁰ The mechanism behind this association is not fully understood. One hypothesis is that acid suppression alters the mother’s gut microbiome or immune signaling in a way that influences the developing fetal immune system, but this remains speculative.

It is worth emphasizing that this is an observational finding, not proof that PPIs cause asthma in children. Women who take PPIs during pregnancy may also have genetic predispositions or environmental exposures that raise their children’s asthma risk independently. Researchers have not been able to establish a clear causal chain. But the finding has been consistent enough across studies that some clinicians factor it into their prescribing decisions, particularly when weighing whether a woman truly needs a PPI versus a milder alternative.

How Esomeprazole Compares to Other PPIs

All PPIs work by the same basic mechanism: they irreversibly block the proton pump in stomach lining cells, reducing acid production. But they differ in how the body metabolizes them, and this has occasionally led to drug-specific safety signals. Esomeprazole is the S-isomer of omeprazole, meaning they are essentially mirror-image molecules. This is relevant because omeprazole was the only PPI classified as FDA pregnancy category C, while the other PPIs, including esomeprazole, were all category B.¹¹ The category C designation for omeprazole was based on animal studies showing dose-dependent embryotoxicity, although the relevance to human use at normal doses has always been debated.

An analysis of the FDA’s adverse event reporting system examined pregnancy-related reports across different PPIs and found that certain signals appeared to be drug-specific rather than shared by the entire class. Omeprazole, for instance, was linked to reports of postpartum hemorrhage and preeclampsia, while lansoprazole and pantoprazole each had their own distinct signal patterns.¹² Esomeprazole did not stand out for any particular pregnancy-related adverse event in that dataset, which is somewhat reassuring given its widespread use. Still, adverse event reporting databases have well-known limitations: they depend on voluntary reporting and cannot establish cause-and-effect.

What Clinical Guidelines Recommend

Major gastroenterology guidelines consistently recommend a stepwise approach to managing reflux symptoms during pregnancy. The American College of Gastroenterology guidelines, along with several review articles, suggest starting with lifestyle changes: eating smaller meals, avoiding food close to bedtime, elevating the head of the bed, and cutting out trigger foods. If those measures are not enough, antacids containing aluminum, calcium, or magnesium are the next step.¹³

If antacids do not control symptoms, histamine-2 receptor antagonists (H2 blockers like famotidine) are generally tried before PPIs. PPIs are reserved for cases where reflux is severe enough to meaningfully affect quality of life or where complications like esophagitis develop.¹⁴ This is not because PPIs are considered dangerous; it reflects a precautionary principle of using the least powerful intervention that works. When a PPI is needed, esomeprazole, lansoprazole, and pantoprazole are all reasonable options. Omeprazole remains commonly used as well, despite its former category C status, because decades of human exposure data have not shown a clear pattern of harm at standard doses.

The step-up framework also acknowledges that reflux during pregnancy often resolves after delivery as the physical pressure on the stomach decreases and hormone levels normalize. If you can manage symptoms with lifestyle changes and occasional antacids for a few months, you may never need a PPI at all. But for the substantial number of pregnant people whose reflux is severe enough to disrupt sleep, eating, and daily function, PPIs remain an appropriate tool.

Practical Considerations for People Making This Decision

If you are pregnant and your doctor has recommended esomeprazole, the cumulative evidence suggests the risk is low but not zero. The birth defect data are reassuring at a class level, with one study flagging a small esomeprazole-specific signal that has not been consistently replicated. The associations with preeclampsia, preterm birth, and infection are modest in absolute terms and are difficult to separate from the underlying conditions that led to PPI use in the first place.

A few practical points are worth keeping in mind. First, use the lowest effective dose for the shortest time that controls your symptoms. PPIs are designed to be taken daily, but some people find that every-other-day dosing or a lower dose is sufficient during pregnancy. Second, be aware that your body clears esomeprazole more slowly during pregnancy, so the standard dose may produce higher blood levels than it would outside of pregnancy. Third, if you are concerned about the infection signal, pay extra attention to food safety, since reduced stomach acid means your gut barrier against food-borne bacteria is somewhat lowered.

Discuss alternatives with your provider. For many pregnant people, an H2 blocker like famotidine works well enough to control symptoms without escalating to a PPI. If your reflux is truly unmanageable on anything less, that is a legitimate reason to use esomeprazole, and the overall safety data support that decision. The worst outcome, practically speaking, would be enduring weeks or months of severe reflux with disrupted nutrition and sleep because of excessive fear of a medication whose risks, while not trivial, are consistently described as small in the medical literature.

The FDA Category System and Why It No Longer Applies

You will still see references to FDA pregnancy categories (A, B, C, D, X) in many drug guides and online resources, but the FDA officially replaced this system in 2015 with the Pregnancy and Lactation Labeling Rule. The old letter categories were considered oversimplified: a single letter could not capture the nuance of whether a drug’s risk profile differed by trimester, dose, or indication. Under the new system, drug labels are supposed to include a narrative summary of the available human and animal data, along with a risk assessment, rather than a single letter grade.

For esomeprazole, the former category B classification meant that animal reproduction studies had not shown a risk to the fetus and there were no adequate, well-controlled studies in pregnant humans. In practice, “category B” was often interpreted by patients and some clinicians as “safe,” which was never quite what the label was designed to convey. The current labeling approach provides more room for context, but the tradeoff is that there is no simple shorthand to reassure or warn patients. If someone tells you esomeprazole is “category B and therefore safe,” the first part is outdated and the second part was always an oversimplification.