When an NHS letter advised a pregnant mum to get the swine flu jab to protect herself and her unborn child, she didn't hesitate.

However, Heather McFarlane, 40, says the inoculation, given to her while she was pregnant in 2009, directly led to her developing the crippling sleep disorder narcolepsy.

The mum-of-three says the illness means that she now falls asleep up to eight times a day.

Heather McFarlane has spoken of the 'devastation' that the narcolepsy, which is believed to be linked to a swine flu jab administered to the mum-of-three while pregnant, has caused

Mrs McFarlane, a teacher from Glasgow, says that she is constantly exhausted and can nod off while doing the dishes, walking downstairs or just chatting to her three children. She can no longer drive and needs regular naps at work.

While pregnant with her third child, she was given the Pandemrix swine flu vaccine, in line with NHS advice for pregnant women.

She says her lawyers are now negotiating a possible £1million out-of-court settlement with drug makers GlaxoSmithKline.

Narcolepsy develops when the body's immune system destroys neurons in a region of the brain known as the hypothalamus. Scientists are researching how Pandemrix triggers this.

Mrs McFarlane is angry that she's missing her children growing up, as she says that she's often asleep at key moments that most mums take for granted.

She said: 'Narcolepsy has devastated my life. It sounds like most people's idea of bliss being able to sleep all day, but it's a living nightmare.'

An associated illness, cataplexy, means Mrs McFarlane can suffer episodes of paralysis. She says: 'I have been robbed of my life and my children denied their mum'

She needs special sleep breaks at work and fears she's missing out on the best years of her life.

Her lawyers have now told her she's possibly due a £1 million compensation payout after apparently developing her narcolepsy in response to an injection she was given that was meant to prevent her from swine flu. The case is on the verge of being settled out of court.

At the time that she was inoculated, fears were rife that an epidemic was set to hit the UK. But she claims her life has been thrown into turmoil by the effects of the new drug.

She also suffers from catalepsy, a terrifying paralysis which means she can go into terrifying seizures in which she freezes, aware of everything going on around her, but unable to say or do anything.

Teacher Heather drops off while standing at the sink, talking to her kids or even while laughing - simple emotions such as sadness, anger or even laughter seem to pull some sort of trigger in her brain.

'I would love to jump in the car and take the girls out for a mum-and-daughter shopping day, but I can't.'I feel that pang of sadness and think how much they are missing out.' Heather McFarlane

Every aspect of her life, from walking down the stairs to the school run, is affected. She needs constant support from her mother and is terrified of the waking paralysis.

'The cataplexy means I can be fully conscious yet terrifyingly paralysed and the narcolepsy makes me sleep. I drop plates, falling asleep while making dinner, and the children have caught them.

'I have been robbed of my life and my children denied their mum.

'I am too tired and asleep all the time.

'Other mums spend time with their children. They have family days out, to concerts, museums, shows and the like.

'I have to depend on my husband Kevin, mum Elly, sister Lorna and friends to help out all the time.'

Global pharmaceutical giant GlaxoSmithKline, the drug company which made the swine flu drug, has indicated it is willing to settle with 100 people in the UK and 800 worldwide.

They include midwives, doctors, nurses and pharmacists because front line health workers were urged to get the jab as their jobs with the public put them at risk.

A spokeswoman for GSK said the company was actively researching the possible association between Pandemrix and narcolepsy.

She said: 'It includes the interaction this vaccine might have had with other risk factors in those affected.

'The vaccination programmes against H1N1 pandemic flu were unprecedented in their scale and speed.

'Because of this, GSK and governments agreed to manage and share the responsibility of answering any legal claims, by allocating between us the costs attributed to investigating and handling cases and any potential compensation if claims are found to have merit.

'Throughout development of our H1N1 flu vaccines there was no data suggesting a potential for an increased risk of narcolepsy among those.

For Mrs McFarlane, the sudden-sleep syndrome has been hardest on Heather's children - Molly, 14, Maisie, 11 and Dougie, five.

The McFarlane family (pictured from left, Maisie, 11, Heather, husband Kevin, Dougie, five and Molly, 14) have had their lives turned upside down by the sleep disorder and now rely heavily on help from Mrs McFarlane's mum to deal with everyday life

'I would love to jump in the car and take the girls out for a mum-and-daughter shopping day, but I can't.

'I feel that pang of sadness and think how much they are missing out.'

Despite constantly nodding off without warning, she says the condition leaves her feeling 'totally exhausted'.

'Narcolepsy wrecks your sleeping pattern and instead of being awake for hours it forces you to doze off several times a day, making you sleep less at bedtime,' she explained. 'It completely disrupts your sleep rhythm.'

The worst part of her ordeal has been the waking, locked-in paralysis she suffers.

'I will laugh at TV programmes and then suddenly feel paralysed. It starts as a feeling spreading down my face.

'I felt totally helpless and locked-in, unable to speak to communicate.

HEATHER'S DIARY: A DAY IN THE LIFE OF A NARCOLEPSY SUFFERER 7am: After six hours' sleep, induced by sleep drugs, she wakes and immediately takes more tablets to keep her awake. They are essential to allow her to make the family's breakfast and prepare her for her teaching job. 8am: Her mum drives the kids to school. She is no longer able to drive. She makes her way to work in a taxi. 8.45am: She arrives at her work prepared to stay awake for her pupils. 10.15am: At the staff break she crashes out in a quiet area with her mobile phone alarm set to wake her in 15 minutes. 12.15pm: Staff lunchtime allows her to get a chance to eat to try to recover weight lost through the drugs and exhaustion. 12.45pm: Heather lies down for another vital sleep with her mobile alarm set for 1pm. Before she was diagnosed and got vital drug treatment, she would fall asleep in front of pupils. 3pm: Pupils leave for home and Heather needs another 15-minute sleep before working on lessons for the following day. 4pm: Her taxi arrives to take her home. Most days she dozes in the back of the cab. The drivers are used to her and know to wake her when she gets home. 4.30pm: Back at home the kids are with her mum, Elly. They are busy with homework and Heather pitches in to ensure it is done. If she hasn't slept well she'll crash out on the couch for 30 minutes. 6pm: A key time when Heather can suddenly fall asleep without any notice. The children help out - ready to catch anything mum may drop. 6.30pm: The family are around the dinner table. Heather may slip off again into another sleep, sometimes even mid-conversation. 8-9pm: Her youngsters are preparing for bed and Heather checks lessons prepared for her pupils tomorrow. 11pm: Heather takes her nightly medication to help her sleep. Without it she would sleep for only two hours then wake through the night because of her wrecked sleep rhythm. A normal day for Heather is punctuated by a series of sleeping sessions, some involuntary. Advertisement

'When it first happened my husband thought I had fallen asleep - but I wasn't and couldn't speak to tell him I was conscious. It's horrible and frightening.

'All this is because I followed NHS advice to be vaccinated for a swine flu epidemic.'

Mrs McFarlane, from Jordanhill, Glasgow, developed her condition after being given the Pandemrix swine flu vaccine, in step with NHS advice for pregnant women.

'I received several letters telling me to get the jab - and I feared the outcome if I didn't,' she said.

'They certainly didn't tell me there hadn't been enough long-term safety trials. I obviously wouldn't have agreed if I had known that.'

The symptoms set in shortly after Dougie was born in 2010.

'I struggled to stay awake but just put it down to being a busy mum,' she said.

After months of worrying tests a specialist doctor at a Glasgow sleep clinic suggested her narcolepsy may be linked to the injection she was given.

She added: 'After over a year of symptoms and desperate to find a cause my GP referred me to a neurologist to try and pinpoint the reason.

'I was given a series of major tests, but nothing showed up. After all the tests and a sleep study at Gartnavel Hospital, I was referred to a sleep disorder consultant and the frightening truth emerged.

'The specialist asked me immediately if I'd had the swine flu vaccine. He must have seen other patients with the same symptoms and here was another.

'I was pleased to be diagnosed, but shocked to discover there is no cure.'

She now has to take a daily diet of strong drugs which have has caused her to lose a massive amount of weight - a stone-and-a-half in just five weeks at one point.

But it's the lost time she can't get back that leaves her feeling furious the most.

'My kids are not getting the mum they deserve,' she adds.

Lawyers have told the mum drug makers GlaxoSmithKline want to settle out of court.

As such she could be set for a seven-figure windfall. Her claim is one of 70 being handled by law firm, Hodge Jones & Allen. Two-thirds of the claimants are children.

The potential £100 million bill for claimants is being settled by the Government because of a deal health officials struck to cover serious side-effects.

Department of Health officials gave an indemnity to GSK covering all adverse reactions after GSK said it could not guarantee the drug's safety because years of trials had not been conducted.

A Department of Health spokesperson said: 'We understand how distressing narcolepsy can be.

'Pandemrix was used to prevent serious illness and deaths during the swine flu pandemic in 2009/10.

'At the time, the possible association with narcolepsy was not known.