Is HBOT safe during pregnancy?

The honest answer depends entirely on why you'd be in the chamber. For a true medical emergency like carbon monoxide poisoning, the published evidence says hyperbaric oxygen therapy (HBOT) is reasonably safe for the fetus and can save its life. For wellness, anti-aging, or "feeling better" reasons, the same evidence does not exist, and nearly every hyperbaric authority treats pregnancy as a reason to wait. This guide walks through what the studies actually found, where the data is thin, and how doctors decide.

The Short Version Before the Details

Pregnancy has long sat in a strange category in hyperbaric medicine. It isn't an absolute "never" like an untreated collapsed lung. It's a relative contraindication, which means the decision turns on the reason for treatment and the trimester. According to StatPearls on HBOT contraindications, "pregnancy has traditionally been considered a relative contraindication to HBOT due to unknown fetal effects."

That single word, "unknown," is the heart of this entire topic. We have decades of emergency case reports for carbon monoxide poisoning. We have almost nothing for elective use. Treat those two situations as different worlds, because the medical literature does.

How HBOT Works and Why Pregnancy Complicates It

In a hyperbaric chamber, you breathe oxygen at a pressure higher than the air at sea level. Sea level pressure is 1 atmosphere absolute (1 ATA). Clinical HBOT runs roughly 2.0 to 3.0 ATA. At that pressure, far more oxygen dissolves directly into your blood plasma, not just the oxygen riding on hemoglobin. That oxygen-rich plasma reaches tissues that normal breathing can't supply well.

That mechanism is exactly what makes the therapy powerful, and exactly why pregnancy raises questions. For a deeper look at the underlying physics, see our explainer on how hyperbaric oxygen therapy works. Three issues come up during pregnancy:

• Fetal oxygen levels. A developing fetus lives in a deliberately low-oxygen environment. Some animal and lab work has raised the theoretical concern that big oxygen swings could affect blood vessel development.
• The ductus arteriosus. This is a fetal blood vessel that should stay open until birth. High oxygen can, in theory, push it toward early closure.
• Retinal vessels. High oxygen exposure in newborns is a known factor in some eye-vessel problems, so the theory has been extended backward to the fetus.

Here's the catch. These are mostly theoretical and lab-derived concerns. The human emergency data, which we cover below, has not borne them out at the pressures and durations used for short emergency treatment. Theory and outcome don't fully line up, and that gap is why the field stays cautious without banning the therapy outright.

What Actually Reaches the Fetus

A point that gets lost in the marketing is that the fetus never breathes the chamber gas. The mother breathes oxygen at pressure, her arterial oxygen content rises sharply, and the fetus receives whatever crosses the placenta. The placenta is a buffer, not a window. Fetal blood oxygen does climb when the mother is hyperoxic, but it climbs far less than the mother's, because the placenta and the fetal circulation blunt the swing. This is one reason short emergency sessions appear better tolerated than the raw pressure numbers would suggest. The fetus is partly shielded.

It also explains the central irony of the CO situation. The very same hyperoxia that worries people in theory is, in CO poisoning, the mechanism that rescues the fetus by driving carbon monoxide off fetal hemoglobin. Whether elevated oxygen is friend or foe depends entirely on what problem you're solving. With CO, you're correcting a deadly oxygen deficit. With wellness use, there's no deficit to correct, so you're left with risk and no benefit.

Pressure Versus Oxygen: Two Separate Exposures

It helps to separate the two things happening in a chamber, because they affect a pregnancy differently. One is mechanical pressure, which compresses gas-filled spaces and matters most for the mother's ears and sinuses. The other is the high oxygen dose, which is the part with theoretical fetal implications. Most pregnancy concern is about the oxygen, not the squeeze. That distinction matters when people assume a "low pressure" mild chamber sidesteps the fetal question. It doesn't fully, because the oxygen is still the variable nobody has studied in pregnancy.

The Strongest Case: Carbon Monoxide Poisoning

This is the one situation where the evidence genuinely supports HBOT in pregnancy, and it's worth understanding why the math flips so hard in the chamber's favor.

Why CO Is So Dangerous for a Fetus

Carbon monoxide binds hemoglobin far more tightly than oxygen does, forming carboxyhemoglobin (COHb) and starving tissue of oxygen. In pregnancy, the danger multiplies. Fetal hemoglobin binds CO with roughly 2.5 to 3 times the affinity of adult hemoglobin, and fetal COHb has a half-life about 4 times longer than the mother's, per the narrative review of HBOT in pregnant women (PMC10352564).

Translation: the fetus soaks up more CO, holds it longer, and clears it slower. A mother can look only mildly sick while her fetus is in real danger. Untreated CO poisoning in pregnancy carries a reported fetal mortality in the range of 36% to 67%, and stillbirth has occurred even when the mother had no serious symptoms.

What the Human Studies Found

Most of this evidence is case reports and small series, not randomized trials. That's a real limitation, but the pattern across them is consistent.

The bottom line from the 2023 narrative review (PMC10352564): "standard HBOT in pregnancy appears to be safe and is considered beneficial, reducing the severity of maternal and fetal injuries." Crucially, the review concluded that when bad fetal outcomes did occur, they tracked with the CO poisoning itself, not the oxygen treatment. In its words, fetal complications "are likely to be related to CO poisoning, but they are not related to HBOT."

The Treatment Window That's Considered Safe

The review found that pressures ranging from 1.4 to 3 ATA for 30 to 180 minutes have been used safely in pregnant patients, with one analysis pointing to 2.4 ATA for 120 minutes as showing no harm to mother or fetus. Because fetal CO clears slower, pregnant patients may need longer sessions than non-pregnant patients to scrub CO from fetal blood.

Many centers also lower the trigger for treating. Pregnant patients are often offered HBOT at COHb levels above roughly 15%, lower than the threshold for non-pregnant adults, precisely because the fetus carries more CO than a maternal blood draw reveals. For the broader emergency picture, see our atlas on HBOT for carbon monoxide poisoning.

How Treatment Is Monitored in a Pregnant Patient

Emergency HBOT in pregnancy isn't done casually. The setup looks different from a routine wound-care dive because two patients are in the chamber at once. A few things change:

• Fetal monitoring. Where feasible and gestational age allows, the fetal heart rate is tracked before, sometimes during, and after the dive. Persistent fetal distress can change how long treatment continues, and the case literature notes that continuing HBOT in the presence of fetal distress findings appears to help rather than harm.
• Lower COHb threshold to treat. As noted, the bar to offer HBOT drops in pregnancy because a "reassuring" maternal blood level can hide a fetus that's still loaded with CO.
• Possibly longer or repeated sessions. Because fetal CO lags maternal CO, the mother may clear her own carboxyhemoglobin while the fetus is still elevated, which can justify extending treatment.
• Obstetric backup. Treatment is coordinated with obstetrics, not run by a hyperbaric team in isolation, so that fetal status and the pregnancy as a whole are managed together.

None of this applies to elective use, which is part of the point. Emergency HBOT in pregnancy happens inside a hospital-grade safety net. A wellness chamber has none of that.

The Other Emergencies: Decompression Sickness and Gas Gangrene

Two other life-threatening conditions can justify HBOT during pregnancy, though the evidence is even thinner than for CO.

Decompression sickness (DCS). This is the scuba-diving "bends," where gas bubbles form in blood and tissue. HBOT is the standard treatment. The wrinkle: a pregnant diver who gets DCS may have bubbles affecting the fetus too, and the fetus has no easy way to filter them. The Divers Alert Network guidance on pregnancy and diving is blunt about prevention. DAN advises women not to dive while pregnant or trying to conceive, because hyperbaric exposure during a dive has been linked in animal and observational reports to low birth weight, miscarriage, premature delivery, and skeletal or cardiac malformations. But if DCS actually happens, recompression treatment is still given. The treatment is for the bubbles already there. The advice not to dive is about avoiding the situation in the first place.

Gas gangrene and necrotizing infection. These are rapidly fatal soft-tissue infections where HBOT is a recognized adjunct. There's no real body of pregnancy-specific data here, just the same logic: a dead mother means a dead fetus, so the maternal emergency wins. See our coverage of HBOT for gas gangrene.

The common thread across all three emergencies is a principle that runs through obstetric medicine: stabilize the mother and you usually give the fetus its best chance. Withholding a life-saving treatment to avoid a theoretical fetal risk often harms the fetus more.

The Weakest Case: Elective and Wellness HBOT

Now the part that matters for most people reading this, because the explosion of "mild" hyperbaric chambers in wellness clinics has put HBOT in front of people who are pregnant and curious.

There is no good evidence that elective HBOT is safe in pregnancy, because the studies have not been done. Every authority that addresses it lands in the same place: don't, at least not while pregnant.

A few things worth saying plainly. Much of the marketing around elective and "mild" HBOT overstates a safety record that doesn't exist for pregnant women. The absence of reported harm from a handful of wellness sessions is not the same as evidence of safety. Nobody has run the trial. And the "it's only 1.3 ATA, it's gentle" argument doesn't help, because the lack of pregnancy data applies to soft chambers just as much as hard ones. For why that 1.3 ATA distinction matters elsewhere, see mild HBOT vs medical HBOT.

If the treatment can wait until after delivery, the conservative and well-supported move is to wait.

What the Guidance Bodies Actually Say

It's useful to see how different sources frame the same question, because the wording reveals the field's caution. None of them say HBOT is broadly safe in pregnancy. They carve out emergencies and otherwise advise restraint.

The pattern is consistent. Emergency, yes, with monitoring. Elective, wait. There is no major authority telling pregnant women that a wellness chamber is a studied, safe choice.

The Wound-Healing Gray Zone

One situation sits between "clear emergency" and "obvious wellness": a problem wound, such as a non-healing diabetic foot ulcer, that genuinely benefits from HBOT in the general population. In a pregnant patient this becomes a judgment call. If the wound is limb- or life-threatening, the emergency logic applies. If it can be managed with standard wound care and the hyperbaric course can wait until after delivery, deferring is the usual choice. The deciding question is urgency, not whether HBOT "works" for wounds. For background on that indication, see our piece on HBOT for diabetic foot ulcers.

What the Animal Studies Actually Show

People cite animal data on both sides of this, so it's worth being precise about what those studies found, because they're genuinely mixed.

• Rat embryos: HBOT "did not induce malformations" at either 3.3 or 4.3 ATA, per the findings summarized in the 2023 narrative review. However, some rat work showed reduced fetal body weight and increased placental weight at high pressures, and an older report bluntly titled "Hyperbaric oxygen causes fetal wastage in rats" (PMID 4183168) found pregnancy losses.
• Explanted rat fetuses: A separate Teratology study (PMID 5446881) examined how isolated rat fetuses developed under hyperbaric oxygen.
• Hamsters: Some hamster studies showed congenital malformations after specific high-pressure exposures, while in hamsters with untreated decompression sickness, the untreated DCS caused the severe defects, and HBOT-treated fetuses looked close to controls.

So what do we take from this? The animal record is not a clean "safe." It shows that under certain extreme pressures and timing, you can produce fetal effects. But it also repeatedly shows that the clinical pressures and short durations used for human emergencies are far gentler than the exposures that caused harm in animals, and that maternal stabilization tends to protect the fetus. The animal data justifies caution. It does not justify panic for a single emergency treatment.

Don't Forget the Mother's Own Risks

Most of this article focuses on the fetus, but HBOT carries the same ordinary risks for a pregnant patient that it does for anyone, and pregnancy can amplify a couple of them.

• Ear and sinus barotrauma. Pressure changes stress the middle ear, and this is the single most common side effect of HBOT in anyone. Pregnancy-related congestion can make ears harder to clear. For technique, see how to equalize your ears in a hyperbaric chamber.
• Oxygen toxicity seizures. Rare at clinical pressures and durations, but real, which is one more reason emergency dosing in pregnancy stays within the studied 1.4 to 3 ATA window rather than pushing higher.
• Claustrophobia and positioning. A growing uterus can make lying still in a monoplace chamber uncomfortable, and anxiety in an enclosed space is common.

These aren't reasons to skip a life-saving treatment. They're reasons the decision belongs with a hyperbaric physician who can manage them, not a wellness clinic.

Trimester Matters

The first trimester is when organs form, so it carries the most theoretical concern, and most guidance is most conservative there. That said, in a true emergency, treatment is not withheld based on trimester. The CO case literature includes treatment across all stages of pregnancy with reassuring maternal and fetal results overall.

For elective use, the trimester question is almost moot, because the recommendation is simply to wait until after pregnancy regardless of stage.

Who This Applies To

Get HBOT, with your obstetrician and a hyperbaric physician coordinating, if:

• You have carbon monoxide poisoning, especially with COHb above 15%, loss of consciousness, neurological symptoms, or any sign of fetal distress.
• You have decompression sickness, gas gangrene, or another recognized hyperbaric emergency.

Do not get HBOT, or wait until after delivery, if:

• You're considering it for wellness, anti-aging, energy, skin, athletic recovery, or general "longevity."
• You're eyeing a home or clinic "mild" chamber while pregnant.
• You have a non-urgent wound that can reasonably wait.

Always loop in two people: your obstetrician and a hyperbaric medicine physician. This is not a solo decision, and it's not a wellness-clinic-front-desk decision. For how to vet a facility generally, see our HBOT safety checklist.

Honest Limitations of the Evidence

It's worth ending on what we don't know, because that's the most useful thing for a pregnant reader.

There are no randomized controlled trials of HBOT in pregnant women. There never will be, for obvious ethical reasons. The CO evidence is built from case reports and small retrospective series, which can't fully separate the effect of the treatment from the effect of the poisoning, and which tend to underreport bad outcomes. Long-term neurodevelopmental follow-up of exposed children is limited. And the entire elective-use question is an evidence vacuum, not a "safe" verdict.

That uncertainty is precisely why the field's stance is so split by context: lean in for emergencies, hold off for everything else.

Frequently Asked Questions

Can I use a hyperbaric chamber during pregnancy for general wellness?

No reputable hyperbaric authority supports elective or wellness HBOT during pregnancy. There are no studies showing it's safe for a developing fetus, and the consistent recommendation is to wait until after delivery. The absence of reported harm from wellness use is not evidence of safety, since the research simply hasn't been done.

Is HBOT safe in the first trimester?

The first trimester carries the most theoretical concern because organs are forming, so elective treatment is especially discouraged then. In a genuine emergency like carbon monoxide poisoning, though, treatment is given regardless of trimester, because a life-threatening maternal condition poses a far greater risk to the fetus than a short, monitored oxygen treatment.

Why is HBOT recommended for carbon monoxide poisoning but not wellness?

Because the risk math is completely different. CO poisoning can kill a fetus 36% to 67% of the time untreated, and the fetus holds CO longer and binds it more tightly than the mother. The proven, life-saving benefit clearly outweighs the theoretical oxygen risk. For wellness, there's no benefit established in pregnancy to weigh against any risk at all.

Does a "mild" 1.3 ATA soft chamber make it safe during pregnancy?

No. The "mild" label refers to lower pressure, not to a stronger safety record. There's no pregnancy-specific evidence for soft chambers any more than for medical-grade ones. Lower pressure does not turn an unstudied therapy into a studied one, so the same advice to avoid elective use during pregnancy applies.

Can scuba diving or recompression treatment harm my pregnancy?

The Divers Alert Network advises against diving while pregnant or trying to conceive, because hyperbaric exposure during dives has been linked in animal and observational reports to birth defects and pregnancy loss. If you actually develop decompression sickness, recompression treatment is still given to treat the bubbles, but the goal is to never put yourself in that situation while pregnant.

Medical disclaimer: This article is for general education and is not medical advice. Hyperbaric decisions during pregnancy must be made with a qualified obstetrician and a hyperbaric medicine physician, who can weigh your specific situation.