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HBOT during pregnancy remains one of hyperbaric medicine's most geographically divided topics. Russia and China routinely treat pregnant women with HBOT for obstetric indications — fetal distress, placental insufficiency, preeclampsia — while Western medicine classifies pregnancy as a relative contraindication, reserving HBOT almost exclusively for carbon monoxide poisoning. Italy developed one of the most detailed clinical programs for treating fetal growth restriction with HBOT at 1.5 ATA — squarely in the "mild HBOT" range — beginning in 1988 and documenting 200 patients. More than 500 pregnant women have been treated with HBOT in documented case series with no harm attributable to the therapy itself, and animal studies establish a clear dose-response relationship showing safety at clinical pressures. Yet no randomized controlled trial exists, and human data on mild HBOT (1.3–1.5 ATA) during pregnancy remains limited to the Italian clinical experience and one German case series. This report synthesizes the complete global literature across all sources.
Russia pioneered obstetric HBOT and still practices it routinely
The most extensive clinical experience with HBOT during pregnancy belongs to Russia, where Soviet researchers began applying hyperbaric oxygenation to obstetric conditions in the late 1970s. As K.K. Jain's Textbook of Hyperbaric Medicine (6th ed., Springer, 2017) states in Chapter 29: "The applications are very limited in the USA and Western Europe, and most of the work has been done in Russia."
Soviet-era researchers treated a broad range of pregnancy complications with HBOT. Aksenova (1979) published early work on HBOT for hypoxic syndrome in pregnancy. Proshina, Kuz'mina, and Borisenko (1983, PMID: 6614362) studied HBOT for prevention and treatment of late pregnancy toxemia (gestosis/preeclampsia) and fetoplacental insufficiency. Pogorelova and colleagues (1983, PMID: 6623996) examined HBOT's effects on placental membrane proteins. By 1988, researchers were using HBOT to prevent chronic fetal hypoxia in pregnant women with acquired heart defects (PMID: 3159284). Burakovskiy and Bokeriia (1977, PMID: 886684) explicitly noted that "the priority of using this method for childbirth by women with severe heart diseases belongs to Soviet medicine," reporting on 136 patients.
Today, HBOT for pregnancy complications remains standard clinical practice at major Russian hospitals. Moscow's Buyanov City Clinical Hospital (GKB im. V.M. Buyanova) offers HBOT to pregnant women under Russia's mandatory health insurance system. The 12th Clinical Diagnostic Center of the Russian Ministry of Defense lists extensive obstetric indications. Russian protocols typically use 1.3–1.7 ATA — notably lower than standard Western clinical HBOT (2.0–2.8 ATA) — with sessions lasting approximately 60 minutes. Treatment courses run 8–12 sessions for active conditions and 5 sessions for prevention. Indications include late gestosis (preeclampsia), fetoplacental insufficiency, fetal hypoxia, threatened abortion, immunoconflict pregnancy (Rh incompatibility), pregnancy with cardiac disease, diabetes in pregnancy, and severe anemia.
Reported outcomes from Russian practice include normalization of uteroplacental blood flow, improvement of placental condition, correction of hormonal levels, fetal growth acceleration of 2–3 gestational weeks, reduction in preterm births and perinatal complications, and improved neonatal neurological outcomes. A study of diabetic pregnancies showed stabilized hyperglycemia and improved microcirculation after 5–6 HBOT sessions (PMID: 6917717). However, nearly all Russian studies are published only in Russian with no English abstracts, making quality assessment extremely difficult. No Russian randomized controlled trials were identified, and the literature reports almost exclusively positive outcomes with limited discussion of adverse events.
The most accessible bridge between Russian and Western approaches is the work of Tchirikov and colleagues (2017–2018), a Russian-trained researcher working in Germany who published English-language studies using HBOT at 1.4 ATA for 50 minutes daily combined with intraumbilical amino acid/glucose supplementation for severe intrauterine growth restriction (IUGR). This combined therapy prolonged the brain-sparing-to-delivery interval by 24 days versus 5.6 days in controls, with no adverse effects attributed to HBOT.
Italy: 200 patients treated at 1.5 ATA — the mild HBOT pregnancy evidence
Italy developed what may be the most detailed clinical program for treating the growth-restricted fetus with hyperbaric oxygen, and it operated at pressures squarely within the mild HBOT range. Beginning in 1988, Italian researchers treated a total of 200 pregnant women with HBOT for intrauterine growth restriction (IUGR), placental insufficiency, hypochromic anemia, and hemoglobinopathies. This body of work, published primarily in Italian-language journals and conference proceedings, has been largely invisible to the English-speaking HBOT community — yet it represents the only documented clinical use of HBOT at 1.5 ATA during pregnancy.
The Italian protocol
The standard Italian protocol used 1.5 ATA (equivalent to 5 meters of seawater) with 100% oxygen for 1 hour per session, over 10 days, with up to 2–3 treatment courses. Each one-hour session was divided into 15-minute oxygen periods alternating with 5-minute air breaks — a standard oxygen toxicity prevention measure. Patients also received vitamins C and E to strengthen antioxidant defenses. Pregnant women were typically admitted before the 35th week of gestation. Some variants of the protocol used slightly different timing: 40-minute sessions every two weeks, or 50 minutes with 2-minute air breaks every 12 minutes of oxygen.
Monitoring was extensive. Fetal response was tracked with ultrasonography (every 2 weeks), Doppler blood-flow measurements (every 4 days), and cardiotocography (every 3 days) during and at the end of each therapy course. Placental function was monitored with daily estriol and HPL levels. After the 35th week, cardiotocography became daily. Crucially, children born after HBOT treatment were followed long-term with regular ophthalmology exams and neuropsychiatric assessments up to school age.
Results
Clinical results were reported as positive across all series. In IUGR cases, the fetal biophysical profile showed improvement as early as the second treatment session. All newborns survived. The treatment was reported to prolong pregnancy time, reduce neurological damage to the fetus, and show a trend toward reduced cerebral damage in the last 4 weeks of pregnancy — although the authors noted this was not statistically significant and was more evident when compared to untreated controls at the same weight percentile. In one documented case from 2011, three sessions at 1.5 ATA with 50 minutes of oxygen produced 160% growth recovery relative to normal gestational age values, with the fetus fully catching up to the normal intrauterine growth curve.
Key researchers
The Italian program involved researchers across multiple institutions:
Benedetto Sparacia (University of Palermo, Sicily) was the most prolific publisher. He authored a full chapter on HBO in pregnancy in the Handbook on Hyperbaric Medicine (Springer, 1996, ed. Oriani, Marroni, Wattel) and published in Minerva Anestesiologica (1991; 57:187–204, PMID: 1944948) and Acta Pediatrica Mediterranea. Sparacia explicitly wrote that HBO is "irreplaceable in improving both placental blood flow and O₂ diffusion at the cellular level."
P.G. Data (University of Chieti) founded Italy's premier postgraduate school in diving and hyperbaric medicine in 1978 and designed the intellectual framework for the fetal treatment approach. Pasquale Longobardi (Centro Iperbarico, Ravenna; SIMSI President 2016–2020) trained under Data and applied the protocol clinically, including on his own son's IUGR in 2011. Gerardo Bosco (University of Padua) contributed the physiological research basis and co-authored the definitive chapter on the Italian approach.
Their chapter, "Treatment of the Small Fetus In Utero with Hyperbaric Oxygenation: The Italian Approach" (in Proceedings of the 2nd International Symposium on Hyperbaric Oxygenation for Cerebral Palsy and the Brain-Injured Child, ed. James T. Joiner, Best Publishing, 2002), brought the Italian pregnancy data to an English-speaking audience for the first time. Earlier Italian contributors include Costagliola and Palotta (1988, Naples), Arduini (1989, Rome — foundational Doppler studies), De Filippo (1991), Paci (1991–1993), and Battaglia (1992, Modena — controlled study showing perinatal mortality reduction from 68% to 29% with maternal hyperoxygenation in IUGR).
The claimed Italian legal mandate
A claim circulates in HBOT communities that Italy had a law mandating HBOT for pregnant women when needed. No such law was found in Italian legislative databases, government directives, or medical regulatory documents. The most likely origin of this claim is the Italian/European guideline that CO poisoning during pregnancy requires HBOT regardless of clinical severity — a specific protocol for emergency treatment that has been misinterpreted as a broader legislative mandate. SIMSI/SIAARTI/ANCIP joint guidelines classify pregnancy in the first trimester as a relative contraindication for non-acute HBOT, not a mandate for treatment.
Why this matters for mild HBOT
The Italian protocol at 1.5 ATA with 100% oxygen delivers a partial oxygen pressure of approximately 1.5 ATA — higher than a mild soft chamber with ambient air (~0.27 ATA at 1.3 ATA) but substantially lower than standard clinical HBOT (2.0–2.8 ATA). It falls at the upper boundary of what is commonly considered the "mild HBOT" pressure range. The fact that 200 patients were treated at this pressure with no reported adverse effects to mother or fetus — and with long-term follow-up of offspring including ophthalmological and neuropsychiatric assessments — constitutes the most significant human safety data for low-pressure HBOT during pregnancy that exists anywhere in the literature.
China officially lists fetal distress among HBOT indications
China possesses the world's largest HBOT infrastructure — over 5,000 modern chambers, more than 2.5 million patients treated yearly, and over 35,000 HBOT-related staff. The Chinese Society of Hyperbaric Oxygen Medicine (under the Chinese Medical Association) includes pregnancy-related conditions among its official indications. Fetal distress and neonatal asphyxia are listed as second-line (adjunctive) indications, while habitual abortion and childbirth in women with heart disease are listed as investigative indications. Pregnancy is not listed as a contraindication in Chinese guidelines — a fundamental departure from Western practice.
Chinese clinical data includes a study of 73 pregnant women who received HBOT (including 17 with fetal distress), all of whom delivered at full term without complications, and a study of 116 pregnant women receiving normobaric saturated oxygen therapy with healthy outcomes. A 2023 prospective study from Xiangya Hospital, Central South University (PMID: 37658414) examined HBOT for thin endometrium during frozen embryo transfer in 146 patients, finding significant reduction in cycle cancellation rates (61.8% to 19.0%, p=0.001) and higher intrauterine pregnancy rates. Chinese treatment protocols use ≤2.0 ATA for pathological fetal hypoxia (IUGR, threatened abortion, fetal distress), with sessions lasting approximately 1.5 hours. For milder physiological hypoxia, normobaric oxygen is used instead.
Japanese practice is considerably more conservative. The most significant Japanese contribution is Yanagawa et al.'s 2023 narrative minireview (Acute Medicine & Surgery, PMC10352564), which analyzed 11 English-language reports of HBOT-treated pregnant women. The authors concluded that HBOT appears safe for CO poisoning in pregnancy but stated that indications for pregnant women "remain unclear" beyond CO poisoning. The Japanese Association for Acute Medicine published this review, and the authors disclosed that they had previously declined HBOT for a pregnant woman with nonobstructive ileus due to unclear indications — reflecting genuine clinical caution.
Latin American research on HBOT during pregnancy is essentially absent from indexed literature. Despite active hyperbaric medicine communities in Brazil, Argentina, and Cuba, no peer-reviewed clinical studies on HBOT during pregnancy from these countries were identified. Latin American HBOT research related to reproduction focuses on fertility and assisted reproduction rather than active pregnancy, with the Asociación Argentina y Española de Medicina Hiperbárica publishing preliminary work on HBOT as an adjuvant for infertility treatment.
Carbon monoxide poisoning provides the strongest pregnancy evidence
HBOT for CO poisoning in pregnancy represents the most extensively documented use case, with more than 510 pregnant women treated across major case series and approximately 15 individual case reports spanning 1987 to 2023. This evidence base has established HBOT as the standard of care for CO poisoning in pregnancy according to both the UHMS and CDC.
The landmark study is Wattel, Mathieu, and Mathieu-Nolf's 25-year prospective cohort (1983–2008) from Nord-Pas-de-Calais, France (Bull Acad Natl Med, 2013, PMID: 25163349). This study followed 406 pregnant women treated with HBOT for CO poisoning and monitored 412 children at day 8, year 2, and year 6. No malformations were reported, and no significant differences in psychomotor development or growth were found compared to matched controls. The authors concluded that HBOT should be used for all expectant mothers exposed to CO poisoning and that no special follow-up is necessary if neonatal status is normal.
Other major series include Elkharrat et al.'s 1991 prospective study of 44 women (34 normal newborns, 2 spontaneous abortions attributed to CO, PMID: 1939875), Arslan's 2021 series of 32 patients at 2.4 ATA with no harmful effects (PMID: 33497969), and Ozgok-Kangal's 2021 series of 28 patients with the longest follow-up (median 34 months, 24 of 28 healthy term infants, PMID: 34547775). Perhaps most compelling is Koren et al.'s 1991 multicenter prospective study (PMID: 1806148): among 5 severely poisoned pregnant women, the 2 treated with HBOT had normal outcomes, while 3 treated with normobaric oxygen alone had 2 stillbirths and 1 case of cerebral palsy.
The pathophysiological rationale for HBOT in pregnancy CO poisoning is particularly strong. Fetal hemoglobin has higher CO affinity than adult hemoglobin, causing fetal carboxyhemoglobin levels to reach 10–15% higher than maternal levels. Fetal CO elimination is 5 times slower than maternal elimination, and the fetus cannot increase ventilation to compensate. HBOT at 2–3 ATA reduces CO half-life to approximately 23 minutes versus 320 minutes on room air. Standard treatment protocols use 2.0–2.4 ATA for 90–120 minutes, typically 1–3 sessions. The consensus from toxicology and hyperbaric medicine is that pregnancy actually lowers the threshold for HBOT — pregnant patients should receive treatment at lower carboxyhemoglobin levels (≥15–20%) than non-pregnant patients (≥25%). Across all published series, adverse fetal outcomes have been consistently attributed to CO poisoning itself, not to the HBOT treatment.
Animal studies reveal a clear dose-response safety curve
Approximately 15–20 animal studies spanning six decades (1960s–2024) across rats, mice, hamsters, rabbits, sheep, and chick embryos establish a dose-response relationship that strongly supports safety at clinical HBOT pressures. The critical variable is pressure × time: standard clinical protocols (2.0–2.5 ATA for ≤90 minutes) fall well below demonstrated harm thresholds.
The earliest and most frequently cited study is Ferm (1964), who exposed pregnant golden hamsters to 3.0, 3.6, and 4.0 ATA for 2–3 hours during early gestation. One quarter of mothers developed CNS toxicity, and fetuses showed exencephaly, spina bifida, umbilical hernias, and limb defects. However, these pressures far exceed clinical treatment levels. In contrast, Sapunar et al. (1993) exposed pregnant rats to 3.2 and 4.2 ATA for 90 minutes daily for 5 consecutive days during organogenesis and found no malformations at either pressure — though fetal body weight decreased (9–17%) and placental weight increased (19–24%) in a dose-dependent manner. This is the study most directly comparable to clinical HBOT protocols.
The threshold for teratogenicity in mice appears to be 2.5 ATA for 2 hours, which produced umbilical hernia and coccyx abnormalities (PMID: 7236475). At 2.0 ATA for 1 hour, no chromosomal damage or teratogenicity was observed. Telford, Miller, and Haas (1969, PMID: 4183168) demonstrated that prolonged exposure — 6 hours at 2–3 ATA — causes fetal cardiovascular malformations and wastage in rats, underscoring that duration matters as much as pressure.
Sheep studies by Assali et al. (1968, PMID: 5648062) provide crucial insight into fetal circulatory effects. At 3.0 ATA with 100% oxygen, maternal arterial PO₂ rose to 1,300 mmHg, yet umbilical arterial PO₂ reached only ~50 mmHg — demonstrating the placenta's significant buffering capacity. The fetal ductus arteriosus constricted, foramen ovale flow dropped by 50%, and the fetus essentially transitioned toward a neonatal circulatory pattern. Critically, these effects were fully reversible upon cessation of HBOT. Fujikura (1964) produced retrolental fibroplasia and 50% neonatal mortality in rabbit offspring through maternal hyperoxia at 3.6–4.0 ATA in late gestation, establishing the upper boundary of fetal retinal vulnerability.
For mild HBOT specifically, the most relevant animal finding comes from a DAN-cited rat study at 1.3 ATA for 70 minutes that showed no significant differences between offspring of HBOT-exposed and unexposed mothers — while a companion study at 3.0 ATA for 8 hours caused cardiac septal defects in nearly half of rat fetal hearts. Gilman et al. (1982–1983) demonstrated that HBOT treatment for decompression sickness in pregnant hamsters was actually protective — untreated DCS caused severe malformations, while HBOT-treated DCS resulted in fewer defects.
The overall animal evidence can be summarized as follows:
- ≤2.0 ATA for ≤90 minutes: No teratogenicity in any species tested
- 2.0–2.5 ATA for ≤90 minutes: Generally safe; standard clinical range
- 2.5 ATA for ≥2 hours: Threshold for malformations in mice
- ≥3.0 ATA for ≥2 hours: Clear teratogenic effects across multiple species
- ≥3.6 ATA: Retrolental fibroplasia, high fetal mortality
Western guidelines classify pregnancy as a relative contraindication only
The global consensus, as codified in standard medical references and major textbooks, classifies pregnancy as a relative contraindication to HBOT — not an absolute one. StatPearls (NCBI, updated 2025) states: "Pregnancy has traditionally been considered a relative contraindication to HBOT due to unknown fetal effects. However, recent studies suggest that HBOT may be beneficial in specific cases, such as carbon monoxide poisoning." The only absolute contraindication to HBOT is untreated pneumothorax.
The University of Iowa Health Care hyperbaric facility provides perhaps the most balanced clinical statement: "Clinical experience has failed to support these concerns and there is no evidence that hyperbaric treatments cause harm to the mother or child. The use of HBO to treat emergency, life-threatening conditions is deemed safe, but elective treatments should probably be held until after delivery if possible." Hilal and Perez's 2025 chapter in Evidence-Based Hyperbaric Medicine (Springer) represents the most current international review, stating HBOT is "generally contraindicated during the first trimester" but "may be cautiously considered in life-threatening scenarios."
The theoretical risks cited in the literature include four main concerns. First, teratogenicity based on animal studies showing malformations at high pressures (≥3.0 ATA) — though clinical protocols use much lower pressures. Second, retinopathy of prematurity/retrolental fibroplasia from fetal retinal exposure to hyperoxia — though this is primarily a disease of prolonged postnatal oxygen exposure in premature infants, not brief prenatal HBOT. Third, premature closure of the ductus arteriosus from elevated oxygen tension — though no cases have been documented from HBOT, and sheep studies show the effect is reversible. Fourth, general fetal oxygen toxicity and oxidative stress — though the placenta provides significant buffering.
K.K. Jain's Textbook of Hyperbaric Medicine dedicates Chapter 29 to "Hyperbaric Oxygenation in Obstetrics and Neonatology," drawing heavily on Russian and Italian research and concluding that HBOT during pregnancy has been shown to be safe. Jain specifically notes: "The Italian physicians began treating the small fetus in utero in 1988 demonstrating a reduction of cerebral damage." The text lists pregnancy among contraindications in Chapter 8 while simultaneously recognizing therapeutic applications. Neither the UHMS nor ECHM has published a standalone position statement specifically addressing pregnancy, though both organizations' affiliated centers treat it as a relative contraindication with CO poisoning as the recognized exception. No registered clinical trial on ClinicalTrials.gov studies HBOT specifically for pregnant women; virtually all HBOT trials explicitly exclude pregnancy.
No definitive harm attributable to HBOT itself (as opposed to the underlying condition) has ever been documented in a human pregnancy. Across all published series — Wattel's 406 women, Elkharrat's 44, Arslan's 32, Ozgok-Kangal's 28, and the Italian 200-patient experience — adverse outcomes were consistently attributed to the underlying pathology (CO poisoning, pre-existing maternal conditions), not to the HBOT treatment. The Yanagawa 2023 review explicitly concluded that all adverse events in HBOT-treated pregnant women "were considered sequelae of CO poisoning, not HBOT."
One important cautionary finding comes from a 2019 American Journal of Obstetrics & Gynecology study showing that even brief hyperoxygenation in pregnant women leads to a significant decrease in cardiac index and rise in systemic vascular resistance that does not return to baseline — an effect not demonstrated in nonpregnant women. The authors cautioned against HBOT use in normoxic pregnant women until RCT evidence is available.
Notable non-CO pregnancy applications deserve attention
Beyond CO poisoning, several documented cases and clinical practices extend HBOT to other pregnancy indications. The Italian program (1988–present) represents the largest body of non-CO pregnancy HBOT experience published in the Western literature, with 200 patients treated primarily for IUGR and placental insufficiency at 1.5 ATA (see Italy section above). Tchirikov et al.'s 2018 study (Physiological Reports, PMC5849598) used HBOT at 1.4 ATA for severe IUGR, building directly on the Italian and Russian tradition and representing the only published non-CO English-language peer-reviewed therapeutic use during pregnancy in an international journal. Sparacia, the leading Italian researcher in this area, described HBO as "irreplaceable in improving both placental blood flow and O₂ diffusion at the cellular level." A 2024 MDPI case report described a 35-year-old woman with sickle cell disease (HbSS) who received 17 HBOT treatments during pregnancy for severe anemia and hyperhemolysis, experiencing significant clinical improvement and delivering a healthy preterm infant. Molzhaninov et al. (1981) managed 170 pregnant women with heart disease using HBOT with no HBOT-related complications, and Vanina et al. treated 54 patients with cardiopulmonary pathology during pregnancy.
Bernhardt et al. (1988, PMID: 3371050) reported HBOT for cerebral air embolism from orogenital sex during pregnancy — demonstrating that emergency non-CO indications are also treated when the risk-benefit calculus demands it.
Mild HBOT during pregnancy: limited but real evidence
The claim that no human data exists for mild HBOT (1.3–1.5 ATA) during pregnancy is incorrect — though the evidence base is far smaller than for standard clinical HBOT.
The Italian clinical program provides the primary human evidence. Two hundred pregnant women were treated at 1.5 ATA with 100% oxygen across multiple Italian centers between 1988 and the early 2000s. The treatment pressure falls at the upper boundary of what is commonly defined as "mild HBOT." No adverse effects to mother or fetus were reported, and children were monitored long-term with ophthalmological and neuropsychiatric assessments through school age. The Data/Longobardi/Bosco protocol, Sparacia's series, and associated publications (Minerva Anestesiologica 1991; 57:187–204, PMID: 1944948; Acta Pediatrica Mediterranea 1992; 8:23–26) collectively constitute the most significant human safety data for low-pressure HBOT during pregnancy available anywhere.
Tchirikov et al.'s 2018 German study adds a second data point at the even lower pressure of 1.4 ATA, used for severe placental insufficiency, with no adverse effects.
Russian clinical practice also overlaps with the mild HBOT range: standard Russian obstetric protocols use 1.3–1.7 ATA, meaning a substantial portion of the (unquantified but likely thousands of) Russian treatments occurred at pressures within the mild HBOT definition.
The theoretical case for mild HBOT safety rests on several arguments. At 1.3 ATA with ambient air (21% O₂), the oxygen partial pressure is only ~0.27 ATA — barely above sea-level breathing — making hyperoxia-related concerns (teratogenicity, retrolental fibroplasia, ductus arteriosus effects) essentially moot. Even with an oxygen concentrator providing ~93% O₂ at 1.3 ATA, partial pressure reaches only ~1.21 ATA, compared to 2.4 ATA during standard clinical HBOT. The pressure of 1.3 ATA is equivalent to approximately 10 feet of seawater — within the range of normal daily elevation changes. A 2024 mechanisms paper (PMC10815786) demonstrated that at 1.5 ATA, ROS production is significantly lower than at 2.5 ATA, with compensatory antioxidant mechanisms (NRF2 activation) engaged.
No clinics were found specifically marketing mild HBOT for pregnant women. Most soft chamber manufacturers and retailers list pregnancy as a contraindication or condition requiring physician consultation, even at 1.3 ATA. Dr. Philip James, a vocal advocate for mild hyperbaric chambers, has criticized the UHMS for dismissing the safety of chambers operating at up to 1.5 ATA but has not published specifically on pregnancy. Dr. Paul Harch, known for low-pressure HBOT research in neurological conditions, likewise has not published on pregnancy applications. The Russian clinical practice of using 1.3–1.7 ATA for obstetric indications represents the closest analog, operating at pressures overlapping with the "mild HBOT" range — but with oxygen delivery through masks inside pressurized chambers rather than ambient-air soft chambers.
An important distinction must be drawn between mild HBOT 1.3 ATA with ambient air and mild HBOT 1.5 ATA with 100% O₂. The oxygen dose differs by roughly 5-fold, and the biological effects would be correspondingly different. The Italian protocol (1.5 ATA, 100% O₂) and Tchirikov's protocol (1.4 ATA, 100% O₂) represent the higher end of mild pressures. The Russian protocols (1.3–1.7 ATA with oxygen masks) overlap with both categories. No published data exists specifically for soft-chamber ambient-air HBOT at 1.3 ATA during pregnancy — making this the remaining true evidence gap.
Conclusion: what the evidence actually tells us
The global evidence on HBOT during pregnancy tells a surprisingly consistent story across disparate traditions. No documented harm to a human fetus has ever been attributable to HBOT itself — across more than 700 cases in formal series (including the Italian 200, Wattel's 406, and other CO poisoning series) and decades of routine Russian and Chinese clinical use. Animal data establish a clear safety margin: clinical HBOT pressures (2.0–2.5 ATA for ≤90 minutes) fall well below teratogenic thresholds, which begin at approximately 2.5 ATA for 2+ hours in the most sensitive species. The placenta provides substantial oxygen buffering, and fetal circulatory changes at high pressures are reversible.
Three critical gaps persist. First, no randomized controlled trial exists for any HBOT use during pregnancy — and likely none will be conducted given ethical constraints. Second, the vast Russian clinical experience (likely thousands of patients) remains largely inaccessible in non-Russian databases, with no detailed safety reporting meeting Western evidence standards. Third, while the Italian program demonstrates safety at 1.5 ATA with 100% oxygen and Tchirikov's work supports safety at 1.4 ATA, no human data exists for soft-chamber mild HBOT (1.3 ATA with ambient air) during pregnancy — a different oxygen exposure profile that would need its own evidence base despite the lower theoretical risk.
The practical state of affairs is this: HBOT for CO poisoning in pregnancy is standard of care globally. HBOT for other obstetric indications (preeclampsia, IUGR, fetal hypoxia) is routine in Russia and China, has been practiced in Italy at 1.5 ATA with documented outcomes in 200 patients, but is considered investigational or off-label elsewhere. Elective HBOT during pregnancy is discouraged in Western practice — not because harm has been demonstrated, but because insufficient controlled data exist to rule it out. The 2019 finding of altered maternal hemodynamics with hyperoxygenation provides the most concrete mechanistic concern. For any clinician or patient considering HBOT during pregnancy outside of CO poisoning, the decision rests on weighing theoretical risks (unsupported by human evidence but grounded in animal physiology) against potential benefits (supported primarily by Russian, Italian, and Chinese clinical experience of uncertain methodological quality).
This article reviews published research from clinical and academic settings. It does not constitute medical advice and does not evaluate any consumer wellness product.
Disclaimer: Individual responses to oxygen and pressure may vary. The inclusion of research summaries on this page does not imply that similar effects can be achieved using non-medical wellness devices.
