WOMEN'S HEALTH
Is it safe to swim outdoors during pregnancy? New study opening doors to find out
The first-of-its-kind review underlines the need for more research to help women make evidence-based decisions
image:
Carmel Lawless sea swimming while pregnant in 2022
view moreCredit: Credit Carmel Lawless
Cold water swimming has increased in popularity in recent years, with risks and benefits increasingly well documented. Now a first-of-its-kind study has focused specifically on the safety of the pastime during pregnancy – and is taking steps to fill the gap in evidence.
Led by the University of Plymouth, the research aimed to answer questions related to the impact of water temperature on the mother and fetal development, as well as whether water quality could impact the baby.
Comprising a group of cold water and exercise physiologists, and specialists in fertility, obstetrics, neonatology, midwifery, water epidemiology and public health, the research team set about finding evidence from existing studies to answer questions that women had asked.
They found just six published studies worldwide relating to pregnant people and cold water swimming and of that number, no study had taken place in a large enough group to offer significant insight, with the studies highlighting large gaps in knowledge.
Expert recommendations
The new research, published in the journal Lifestyle Medicine, contains a list of expert-led recommendations for pregnant people, based on the expertise of the authors involved.
This includes advice to only swim in cold water during pregnancy if a person is a regular cold water swimmer before pregnancy; do not swim alone; and avoid cold water swimming altogether if blood pressure is raised or very low. The authors highlight that these are informed, consensus-led expert opinions in the absence of specific studies, and underline the need for further research.
“I felt guilty and irresponsible”
Carmel Lawless, who lives in Plymouth, enjoyed cold water swimming, and planned to continue the pastime when she became pregnant in 2022. However, the lack of research meant she felt guilt every time she went – so she welcomes the new study and future plans.
She said: “There are so many physical and mental health benefits to sea swimming that I didn’t want to stop but I felt guilty and irresponsible every time I entered the water. It was reassuring yet frustrating that I – along with others seeking to swim outdoors during pregnancy – were all being told to abstain not necessarily because it was too dangerous but because there wasn’t enough evidence of what the risks might be.
“More research would enable us to have open conversations with healthcare professionals, make informed decisions and minimise the risk to ourselves and our children.”
The experiences of Carmel and other pregnant people who enjoy outdoor swimming was part of Immersion Maternal, an exhibition at The Box in Plymouth. The exhibition delves into why people choose to swim outdoors during pregnancy, with an academic study set to accompany it later this year.
What the researchers say
Professor of Maternal and Family Healthcare at the University of Plymouth, Jill Shawe, is the new study’s lead author. She said: “Getting pregnant can lead to a mum-to-be to stop or start certain pastimes to support her health and the baby’s development. However, 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.
“Last year, I was part of a study specific to women’s experiences of cold water swimming (read here). Now, with this new study in pregnant women as a launchpad, we have meetings planned to look at next steps, including prioritising studies working with pregnant women to ascertain their experiences, and directly measuring the impact of cold water swimming on the fetus too. We know the impact of water quality is also a concern, and we’re in touch with various agencies to look at this.”
The research was co-authored by experts from: Bournemouth University; University College London; University of Portsmouth; Royal Sussex County Hospital; University Hospitals Sussex; Scottish Environment Protection Agency; Brighton and Sussex Medical School; the Bluetits Chill Swim Ltd, and Chelsea and Westminster NHS Foundation Trust.
Gail Bainbridge, from the Bluetits Chill Swim group, said: “As a free, inclusive activity, cold water swimming is a fantastic activity to take part in and anecdotally we have people share regularly with us about health improvements both physically and mentally. Once people have experienced the benefits of cold water they generally don’t want to stop. Many people ask about the risks associated with cold water and pregnancy but are finding their GPs and healthcare providers just don’t know. Any research is welcome as it provides people with the information they need.”
Mark Harper, from Royal Sussex County Hospital and Medical Advisor to the Outdoor Swimming Society, added: “‘Is it safe to swim in cold water when pregnant?’ is one of the most frequent questions I’m asked in my role. As more and more women enjoy the benefits of outdoor swimming, it is understandable that they want to continue the activity should they become pregnant. During this time, the body is put under physiological stress so the feeling of wellbeing and weightlessness can be even more welcome. Although there are many anecdotal reports of the activity being both beneficial and safe, there is a dearth of clinical research. This study is therefore important and timely because, by amalgamating the perspectives of both researchers and participants, it will ensure further studies are relevant to all involved in outdoor swimming.”
Professor Joyce Harper, from the Institute for Women’s Health at University College London, said: “Understanding the effects of cold water swimming on women throughout different stages of life is crucial. This includes its impact during menstruation, while trying to conceive, pregnancy and through perimenopause and beyond. More research is needed to address the many questions women have about these experiences.”
Journal
Lifestyle Medicine
Method of Research
Literature review
Subject of Research
People
Article Title
Cold Water Swimming and Pregnancy: A Scoping Review and Consensus Recommendations
Article Publication Date
24-Feb-2025
How the microbiome influences female fertility？
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Schematic diagram showing the proposed mechanisms of SCFAs in the female uterus.
view moreCredit: Manish Kumar, Luhan Jiang, Hoi-Lam Lai, Cheuk-Lun Lee, Ernest H. Y. Ng, William S. B. Yeung, Kai-Fai Lee.
For decades, the uterus was believed to be a sterile environment, but recent research has upended this idea, revealing a diverse microbiome that may influence fertility and reproductive health. A new review published in Reproductive and Developmental Medicine explores how microbial communities in the female reproductive tract—especially Lactobacillus spp.—affect embryo implantation, pregnancy success, and gynecological diseases.
Researchers from the University of Hong Kong analyzed recent studies on the reproductive microbiome and its effects on fertility. They found that a Lactobacillus-dominated (LD) uterine environment significantly improves pregnancy outcomes. Similarly, pregnancy success rates were higher in LD environments.
Lactobacilli help by maintaining a low pH in the reproductive tract, preventing harmful bacteria (like E. coli) from taking over. Other microbes, such as Bifidobacterium spp. (acetate producer), Prevotella spp. (acetate producer), Eubacterium spp. (Butyrate producer) and Enterobacter spp. (propionate producer), may play a role, producing short-chain fatty acids (SCFAs) that regulate immune responses crucial for embryo implantation.
The study highlights that women undergoing IVF who had a non-LD uterine microbiome were far less likely to achieve pregnancy. Additionally, disruptions in microbiota composition have been linked to conditions such as chronic endometritis, endometriosis, and recurrent implantation failure (RIF).
“A disturbed microbiome may create a hostile environment for embryo implantation” said Dr. Kai-Fai Lee，the corresponding author. “This could explain why some women struggle with unexplained infertility despite having no obvious reproductive issues.”
These findings underscore the need for more targeted fertility treatments, including microbiome-based interventions. The researchers suggest that probiotics or personalized treatments to restore a healthy microbiome could improve fertility outcomes, particularly for women struggling with IVF failure.
Journal
Reproductive and Developmental Medicine
Method of Research
Experimental study
Article Title
Impact of microbiota on female fertility and gynecological problems
