ONE of Scotland's highest profile multiple sclerosis sufferers has spoken of how her symptoms almost vanished during pregnancy in a mysterious phenomenon that continues to puzzle researchers.

Elizabeth Quigley, a BBC journalist and wife of Finance Secretary John Swinney, had been struggling to walk unaided, write or use a computer keyboard until she fell pregnant with the couple's first child, Matthew, in 2010.

Ms Quigley, 40, then found her co-ordination and mobility suddenly improving, and her physical strength restored almost overnight.

She said: "I might have had more trouble walking as my pregnancy wore on but my MS-style walking was definitely much easier.

"Of course, at the back of my mind I was thinking 'I'm going to have a baby – will I be strong enough to lift the baby? It'll be really distressing if I can't'. Then I have the baby and I'm moving Matthew about and only afterwards realising 'I didn't think I could do that – that's strange'."

Relief from her MS symptoms continued for a further nine months after Matthew was born, but have since returned.

The effect of pregnancy in alleviating the symptoms of auto-immune disorders such as MS has been observed by scientists as far back as the 1930s. The same pattern is also seen in conditions including rheumatoid arthritis and thyroid malfunctions. However, the cause and how to mimic it outside of pregnancy remains one of medicine's most elusive quests.

MS affects 7500 women in Scotland, three times more than men.

Ms Quigley, who lives in Perthshire with her husband and son, now 19 months, said she had been "vaguely aware" of the phenomenon since being diagnosed with the condition 12 years ago but, having experienced it for herself, embarked on recording a documentary on the issue in an attempt to find an explanation for the effect.

"I've iearned that it's something very elusive that's happening," said Ms Quigley. "They kind of know that it's pregnancy hormones that are coursing through you while you're pregnant, but I wanted to know not only what was happening but why can't you replicate it?"

Although more than 2000 research papers have probed various aspects of the "pregnancy effect" a definitive explanation remains out of reach.

One suggestion has been to imitate the elevated levels of the sex hormones progesterone and oestrogen which flood the body immediately after conception.

However, there is an increasing sense that a one-size-fits-all pill will be impossible as evidence emerges that the effect operates differently across different auto-immune disorders.

"I went into it with lots of questions and came away without a complete answer," said Ms Quigley. "But, having spoken to the other people who've had the same experience, we all came away thinking it would be quite good to have this effect all the time. It was an added bonus – but the big bonus was having our little boy."

l The Miracle Cure called Pregnancy? is on BBC Radio Scotland on Sunday.