By Jane Elliott
BBC News health reporter
For the whole of Liz Pringle's pregnancy and for a few months afterwards her body was free from the pain which had haunted her for years.
Liz's symptoms disappeared when pregnant
Even daily activities such as getting up from a chair or dressing had become agony for Liz, who has rheumatoid arthritis (RA).
"Some times I could not even go down the stairs or put my underwear on because I could not lift my shoulders.
"My hips were always hurting and even when I was opening the door I felt as though my wrist was broken."
"I was diagnosed with RA as I was training to be a nurse and every day there was another ache or pain. I thought I was becoming a hypochondriac."
Affects more than 400,000 people in the UK
Causes inflammation of multiple joints, cartilage loss and bone erosion, leading to joint destruction
Can affect other tissues, such as lungs, eyes and bone marrow
After ten years fewer than 50% of patients can work or function normally on a day-to-day basis
But as soon as Liz, aged 32, from Leeds became pregnant the pain stopped.
"I noticed immediately. I did not have any pain in my knees or hips.
"Before, even lying in bed I had felt bad. But now I found I could run up steps and get up without stiffening up.
"I felt normal for the first time since I had been diagnosed and it was heaven.
"It lasted for the whole of my pregnancy and for some time afterwards, but about four months after the birth I had to stop breast feeding because it had got too painful and I could not hold my daughter, Olivia."
Originally, Liz had been on anti-inflammatories and the drug hydroxychloroquine to help ease her pain.
But when she started trying for a baby she came off the drugs and went onto low-dose pain-killers and calcium.
Nobody knows why women with RA go into remission during pregnancy, but the Arthritis Research Campaign (ARC) is funding a two-year project with more than £160,000 of funding to try to find out.
And although the work is still in its early stages, the scientists working on it are hopeful that it will ultimately lead to new hormonal treatments which can be used to control RA in patients.
Dr Ehrenstein is hopeful of a breakthrough
The team is led by Dr Alex Betz - an immunologist at the MRC Laboratory of Molecular Biology in Cambridge - and Dr Michael Ehrenstein - a consultant rheumatologist at University College, London.
Their team will be looking at special immune system cells which seem to play a role in pregnancy-induced remission - the regulatory T cells.
It is already known that female sex hormones play a large part in easing RA during pregnancy, but it is not known why.
Women who take the drug HRT and the contraceptive pill also have respite from their symptoms, but as soon as they stop taking them their condition flares up again.
The scientists are now hoping to recruit about 15 women volunteers with RA with a view to monitoring them through pregnancy and for about a year after.
They will take blood samples from the women and see if they can observe how the cells function.
Mimic the effect
Dr Ehrenstein is hopeful about the outcome of the research.
"It is almost universal that pregnant reheumatoid arthritis patients do get better," he said.
"If we understand how pregnancy makes the difference we have seen in these cells and how it is doing what it is, then we can target the pathway and mimic not the pregnancy, but the effect on the cells."
However, Dr Ehrenstein said at this stage the mechanism underlying the changes in the T cells is still unclear.
His colleague, Dr Betz said it had been shown that during pregnancy the number of regulatory T cells expands substantially to prevent the rejection of the foetus.
"The expansion of these regulatory T cells - which appears to be driven by the elevated hormone levels caused by pregnancy - has a beneficial effect on RA patients, and leads to an improvement in symptoms.
"It seems that these cells, instead of activating the immune system, actually dampen it down."
Liz said a breakthrough would be good news for RA sufferers like herself.
"I think it would be fantastic if this worked because you quickly forget the pain when you are having a good day.
"People think this is an old people's disease and it must be so much worse when you are older and can't get around as well. It has been quite debilitating."
A spokeswoman for ARC said it was hoped the research would bring some practical benefits.
"We hope our research will have a direct practical benefit for women with RA, by ultimately developing a hormone treatment to keep their condition under more effective control."
Dr Ehrenstein would like any pregnant RA patients who would like to take part in his study to contact him on 0207 380 9281.