By Jane Elliott
Health reporter, BBC News
The harness hopes to avoid miscarriage
After a pregnant woman was prosecuted for failing to wear a seatbelt, inventor Stephen Weston was inspired to try and find a solution.
The woman had not worn a belt because she was concerned it could harm her unborn foetus in the event of a crash.
Stephen said his wife suggested the project to him.
"I was surprised there was nothing there already.
"But there are two problems with the ordinary seatbelt. One is the lap strap which people let ride up, and if you are in an impact it can hurt the foetus.
"The second is the diagonal strap where the same thing can occur.
"There are guidelines put out by the Royal Society for the Prevention of Accidents (RoSPA) and the police.
"They recommend putting the lap strap underneath the bump and the diagonal strap around the bump and between the breasts.
"But cars are all different shapes and sizes and so are pregnant ladies, and to try to get the seatbelt in the right position for everyone is nigh on impossible."
A survey of 400 pregnant women by Loughborough University in 2004 found 87% did not wear seatbelts correctly.
Other studies show that only 11% of pregnant women wear their seatbelts according to government guidelines and that many mothers-to-be do not wear a seat belt at all.
But even an accident at 15 miles per hour can cause a pregnant woman to miscarry, so Stephen aimed to come up with a more comfortable solution.
Gap in market
He hit on with the idea of having a harness which would take pressure away from the abdomen.
"The shoulder harness is used all over the world, from child reins to building sites and it is accepted that that is a very safe and secure method of restraining people either in an accident or a fall.
Stephen tested his idea by putting a trouser belt around his chest and the diagonal of the seatbelt behind him before hitting the brakes.
"The new design moves the traditional diagonal strap away from the bump, and the force of the impact is actually taken on the shoulders and the chest, above the stomach. Obviously it doesn't then affect the foetus.
Some pregnant women refuse to wear a seatbelt
Professor Clive Chirwa, president of the road traffic safety authority at the European Commission and the editor of "Crash Test Worthiness" magazine has carried out early tests on the restraint in his unit at Bolton University.
He agreed there is a gap in the market.
"This four point seatbelt would protect the mother and foetus - there is nothing like it on the market.
"We did some analysis on the restraint and it performs extremely well. We have not tested on a pregnant dummy so far, but expect to do that soon."
Stephen said he believed the seatbelt could have great potential.
"Expectant mothers shouldn't have to choose between comfort and safety. There are no other products which can completely remove the need for the diagonal strap to be positioned awkwardly across the body," he said.
"We believe we can save thousands of women the pain and agony of losing an unborn child in car accidents."
He hopes to have the harness, which would attach to a traditional seatbelt, ready for sale this summer.
Duncan Vernon, road safety manager at RoSPA, said: "It's difficult for us to comment on specific products as the testing which manufacturers put their products through can vary and there is no standardised crash test which they must meet.
"The Department for Transport has a guidance leaflet about wearing a seat belt while pregnant and we recommend that expectant mums initially take a look at that.
"With any product which interacts with the seat belt, drivers would also need to speak to the manufacturer of their car to see whether they advise its use and to find out how it would interact with other safety devices such as airbags."