BBC News Online talked to one mother-of-two who almost fell victim to the illness.

Clare Giles did not recognise the early warning signs of pre-eclampsia before it was almost too late.

Her specialists told her that had she waited just a few days more before heading to hospital, she would not be alive today.

It was extremely painful, but my GP and the hospital told me that it was nothing out of the ordinary

Clare Giles

Clare, 33, now has two normal, healthy children.

However, she fell prey to pre-eclampsia in her first pregnancy, in 1999.

She told BBC News Online: "I didn't get many of the classic symptoms of pre-eclampsia, such as headaches.

"Instead, at 32 weeks, I started swelling up quite rapidly - beginning at my ankles and moving up my legs.

"It was extremely painful, but my GP and the hospital told me that it was nothing out of the ordinary and not to worry."

Dangerous

However, six weeks later - just days before she was expected to give birth - the situation had become much worse.

"The fluid swelling had reached my chest.

"I had put on five stone in four weeks, and it was so bad that the top of my legs were each three feet across.

"When I stood up, my toes were bent an inch off the ground."

She said she did not know much about pre-eclampsia, and the absence of many of the usual symptoms made it hard to spot.

I had put on five stone in four weeks

Clare Giles

However, at this point she knew something was badly wrong, and was taken into hospital, where the problem was finally diagnosed.

"All my blood tests were off the scale.

"I had an appointment scheduled for the end of the week. The doctor said that if I had tried to wait for this, I wouldn't have made it."

She was offered a place on the Magpie trial - looking at the potential of magnesium sulphate injections to prevent pre-eclampsia turning into eclampsia.

All the patients in the trial were randomised to receive either the active injection, or a placebo, and Clare does not know into which group she was placed.

But she feels that there is a good chance that a magnesium sulphate jab saved her life.

"If it can help other women in my position, it will be a great advance."