Despite current NHS advice advocating swimming as a fab exercise for mums-to-be, scientists are warning women that taking a dip can increase their unborn baby's likelihood of developing eczema and asthma later in life.
The not-entirely-water-tight claims are in a report in the British Journal of Dermatology, where experts state that airborne chemicals from chlorine used in swimming pools could affect a developing foetus's immune system.
The Telegraph reports that boffins have been investigating the fivefold rise in people with atopic allergies over the last 50 years.
They say the increase has already been linked to such factors as people washing their skin more often, and having less exposure than before to vitamin D, but add that they now believe chemicals given off by chlorine are an additional risk.
In a review of the existing evidence, the scientists concluded that 'exposure to certain airborne chemicals during pregnancy and in early life may play a contributory role in influencing susceptibility to atopic allergy'.
Despite their assertions, The Telegraph quotes Dr John McFadden, consultant dermatologist at St John's Institute of Dermatology saying there needs to be more research into the findings - and that they haven't 'proved' anything.
"We in the science world are still struggling to find the exact cause of this rise. Several theories have been put out there, including the hygiene hypothesis and others like vitamin D. We have now postulated another possibility," he said.
"We have not proved anything, we are not saying this is the cause, this is a hypothesis but we do know we are using far more chemicals than we did 50 years ago, whether it is in personal care products or processed food and we think this should be looked at and studied more."