When researchers at the University of Plymouth set out to review everything science knows about ice baths during pregnancy and cold water immersion for pregnant women, they expected gaps. What they found was closer to a void. Across the entire global research literature, six published studies met their criteria. None were randomised controlled trials. None were large enough to draw firm conclusions. None were designed to answer the question you’re almost certainly here to ask: is this safe?
“There’s so little out there about cold water swimming in pregnancy that women are left in the dark when it comes to making a decision on whether to continue swimming or not,” says Professor Jill Shawe, who led the review team. If you’re reading this because you already practise cold water immersion and you’re pregnant or planning to be, that frustration is probably familiar. You’ve searched. You’ve found articles that lean toward “it’s fine if you’re careful” or “don’t risk it,” and neither seems to be working from much actual evidence.
They aren’t. And that honesty is where useful guidance begins.
What the first expert consensus actually found
Published in January 2025 in the journal Lifestyle Medicine, the Shawe et al. scoping review is the first serious attempt to consolidate what’s known and build a framework for pregnant cold water swimmers. Shawe assembled a deliberately multi-disciplinary team: obstetricians, midwives, exercise physiologists, cold water researchers, and experienced open water swimmers. They reviewed the available literature, then developed consensus recommendations through structured expert agreement.
Recommendations from the review are graded mostly at level 4, meaning expert opinion, because the underlying evidence doesn’t support anything higher. And the team was transparent about the limitation. They weren’t pretending to have answers the research hasn’t produced. They were trying to give women something more structured than silence.
Within that gap, the team assembled practical considerations that amount to the best available guidance, anchored by a clear distinction between women who are already practising cold water immersion and women who are not.
Dr. Mark Harper, a consultant anaesthetist and cold water researcher who contributed to the review, has pointed out why the evidence gap is unlikely to close quickly. Conducting a clinical trial that deliberately exposes pregnant women to cold water immersion raises ethical problems that may be insurmountable. Observational data, asking women about their real-world experiences, may represent the best evidence we’re going to get for some time.
Why the body’s response to cold matters more during pregnancy
To understand why cold water immersion is not physiologically trivial during pregnancy, you need to understand three things your body is already doing and what cold adds to each.
Your cardiovascular system is already working harder. During pregnancy, blood volume increases by 30 to 50 per cent and cardiac output rises correspondingly. Your heart rate climbs. Your vascular system dilates to accommodate the extra volume. This is normal, healthy adaptation, but it means your cardiovascular system is running with significantly less spare capacity than usual.
Cold water immersion triggers an immediate cardiovascular response: peripheral blood vessels constrict, blood pressure spikes, and the heart has to work against increased resistance. In a non-pregnant person with a healthy heart, this is a manageable stress. During pregnancy, you are adding that stress to a system already operating near its expanded capacity. For women with pre-eclampsia, gestational hypertension, or undiagnosed cardiac conditions, the additional load becomes a more serious concern.
Cold constricts blood vessels, including those that supply the placenta. A study examining cold stress and uterine blood flow found that cold stimulus induces constriction of the uterine artery, reducing placental blood flow. That vasoconstriction finding tends to generate the most concern, and rightly so. Reduced placental blood flow, if sustained or severe, could theoretically affect oxygen and nutrient delivery to the fetus.
The word “theoretically” is doing real work in that sentence. Dr. Katherine Fraser, a practising obstetrician and open water swimmer, has offered clinical nuance on this point: cold water causes surface vasoconstriction and may raise blood pressure slightly, but core vessels are not typically affected in the same way, and she would not expect placental blood flow to be meaningfully reduced during a brief immersion. That is an expert clinical judgement, not a research finding, but it’s an important counterweight to the alarm the vasoconstriction data can provoke.
The cold shock response is the acute risk, and it habituates. When an unhabituated person enters cold water, the body triggers a cascade: gasping, hyperventilation, a sharp rise in heart rate and blood pressure, and in rare cases, cardiac arrhythmia. This cold shock response is the mechanism behind most cold water deaths, which tend to happen in the first minutes of immersion, not from hypothermia.
Prior experience changes this picture at a physiological level. A systematic review by Tipton and colleagues found that the cold shock response habituates after approximately four immersions. Experienced cold water users have a significantly attenuated response: less gasping, a smaller cardiovascular spike, faster stabilisation. A woman who has been practising cold immersion regularly for months or years will not experience the same acute stress as someone stepping into cold water for the first time.
The distinction that matters most: continuing versus starting
If you take one thing from this article, it should be this: the expert consensus draws a firm line between continuing an established cold water practice during pregnancy and beginning one.
Dr. Malika Felton, who contributed to the review, has put it plainly: the expert team is not recommending that pregnant women start cold water swimming without previous experience. For women who are already participating, the review outlines extra considerations and modifications rather than a blanket prohibition.
Behind this distinction sits the habituation research. A woman with an established practice has already adapted to the cold shock response. Her cardiovascular reaction to immersion is blunted. She knows her own tolerance, recognises her body’s signals, and is less likely to panic or hyperventilate. She is, in physiological terms, a different subject from a novice.
Continuing does not mean continuing unchanged. The review recommends reducing intensity and duration from a pre-pregnancy baseline, never immersing alone, choosing locations where exit is easy and help is accessible, and exercising particular caution in the first trimester, when the risk of miscarriage is highest and organ development is most active. Close attention to how you feel, stopping at the first sign of discomfort, is emphasised throughout.
For women who don’t already practise cold water immersion, the recommendation is straightforward: pregnancy is not the time to start. The combination of an unhabituated cold shock response and the cardiovascular demands of pregnancy creates a risk that has no proven upside to justify it.
A separate 2020 paper by Gundle and Atkinson hypothesises that habitual cold water swimming before pregnancy may attenuate the stress response in ways that improve obstetric outcomes. It is an intriguing idea, worth knowing about if you’re planning a pregnancy and already swim in cold water. But it remains a hypothesis, untested beyond the theoretical paper, and not a reason to start.
Cold showers are not the same thing
One practical distinction that gets lost in most coverage of this topic: a cold shower and full-body cold water immersion are different physiological events. A shower exposes a fraction of your body surface area. You control the temperature, the duration, and the coverage. The cardiovascular load is modest and the cold shock response, if it occurs at all, is minimal compared to submersion.
Full immersion exposes your entire body simultaneously. The thermal shock is systemic and the cardiovascular response is immediate. The difference is not one of degree; it’s one of kind. The Shawe review focused specifically on cold water swimming and immersion because that is where the physiological concerns concentrate. Cool showers were not identified as carrying comparable risk.
If full immersion feels like too much right now but you want to maintain some form of cold exposure, a distinction worth raising with your healthcare provider.
A note on environment
Where you immerse matters. The Shawe review’s practical recommendations, including not swimming alone, choosing accessible locations, and ensuring medical support is reachable, implicitly favour controlled environments over open water. A staffed wellness facility with a set temperature, a shallow plunge pool, and someone nearby is a different risk context from a lake or coastal water where conditions vary and exit may be difficult. Open water is not unsafe for experienced pregnant swimmers, but the margin for error is smaller during pregnancy, and a controlled setting reduces several variables at once.
What to discuss with your healthcare provider
Most GPs, midwives, and obstetricians have not been trained on cold water immersion during pregnancy. No major body, not NICE, not ACOG, not the Royal College of Obstetricians and Gynaecologists, has published formal guidelines. The Shawe review is the first attempt to consolidate guidance, and it has not yet filtered into standard clinical education. You may need to bring the information to the conversation rather than expecting your provider to have it.
Here are specific questions worth raising at your next appointment:
About your individual risk profile: Do I have any cardiovascular conditions, blood pressure concerns, or pregnancy complications that would make cold exposure higher risk? Is there anything about my pregnancy specifically that should rule this out?
About your existing practice: I’ve been doing cold water immersion regularly for [duration]. Given that the cold shock response habituates with repeated exposure, does my prior experience change your assessment?
About timing: Are there stages of pregnancy where you’d advise extra caution or stopping altogether? The expert consensus suggests particular care in the first trimester.
About modification: If I continue, what modifications would you recommend in terms of duration, temperature, and supervision?
About warning signs: What symptoms should prompt me to stop immediately? What should I watch for in the hours after a session?
About breathing techniques: Some cold immersion practitioners use controlled hyperventilation techniques such as Wim Hof breathing. The expert consensus advises against breath-holding and forced breathing exercises during pregnancy due to the risk of reduced oxygen to the fetus. Is this something I should avoid even outside of immersion?
Bringing the 2025 Shawe et al. review to your provider gives a credible reference point. Published in a peer-reviewed journal by a multi-disciplinary team including obstetricians, the review is the closest thing to an authoritative source that currently exists.
What honest guidance looks like
The absence of evidence is not evidence of harm. But it is also not evidence of safety. Both of those statements are true at the same time, and the discomfort of holding them together is the honest starting point for a decision.
If you already practise cold water immersion, you are not starting from zero. Your body has adapted. Your risk profile is different from a novice’s, and the expert consensus reflects that difference. You have a reasonable basis for a conversation with your healthcare provider about continuing with modifications. You also have a reasonable basis for deciding the uncertainty is too much right now. Both are legitimate choices, and neither requires apology.
What you have now that you didn’t have before reading this is a clearer picture of why the uncertainty exists, what the specific physiological concerns are, and what the best available expert thinking recommends. That won’t resolve the question. But it means the next conversation you have about it, whether with your midwife, your obstetrician, or yourself, starts from something more solid than silence.
