A Hamilton man has developed clothing designed to shield foetuses from cellphones and electrical appliances, but scientists say there's no proof such shields are necessary.

Neil Bullock developed the MummyWrap, a sleeveless, loose-fitting garment for pregnant women made from a light-weight copper-based cotton fabric known as Swiss Shield.

Mr Bullock said there was "mounting concern" about the effects on developing babies of what he called "electrosmog" - the electro-magnetic radiation (EMR) generated by microwave ovens, TVs, computers and wireless communications including cellphones.

"There's a lot of concern worldwide about electro-magnetic radiation and we can't get away from electronics - it's invasive and it's all around us," Mr Bullock said.

"We do not suggest the garment will totally protect unborn babies, but it will certainly minimise the risk from EMR."

Swiss Shield is used in Europe as curtaining in homes as protection from cellphone towers and powerlines.

Mr Bullock said he expected interest from those in the path of Transpower's proposed 400Kv grid upgrade through the Waikato. He had approached curtain makers with the fabric but had received no interest. He was not scaremongering to sell the product, he said.

"There is a fear factor to a degree but it's a question of how much protection you want to give an unborn child. If you have taken the trouble to get pregnant . . . then (people) want to protect their baby."

National Radiation Laboratory scientific adviser Owen Kilgour said there was no scientific conclusion either way on whether EMR was a risk to babies in the womb.

While the fabric would offer some protection against high-frequency radiation like cellphones and appliances, it would not protect against low-frequency magnetic fields that were the main concern with power lines.

"It could easily be misleading for this product to be marketed to people concerned about the proposed Waikato line," Mr Kilgour said.

"Most people's concerns relate to magnetic field exposures and this product will do nothing to shield them."

Electro-magnetic consultant John Churchill liked the MummyWrap garment enough to advise Mr Bullock on its development, but says he has no financial interest in the venture.

"It's not snake oil, it's a proven product . . . the science behind it is strong and valid and it makes no claims for anything it can't do."

He said it was hard to quantify the effects of EMF on unborn children, but described the MummyWrap as "prudent avoidance" of a possibly harmful substance, like pregnant women avoiding caffeine.

The MummyWrap was designed by Hamilton firm Tripod Design and is made by city clothing manufacturer Trio Sports. Mr Bullock said there were other garments available overseas using similar materials but he was unaware of any made especially for pregnant women.

Mr Bullock has had 10,000 garments made and hopes to sell most offshore through his website at $NZ93 each.

- © Fairfax NZ News