SCOTLAND'S largest health board has said patients affected by a mystery dip in success rates at its IVF unit will be offered a complimentary cycle of treatment.

It came as The Herald revealed an investigation had been launched after a sudden fall in the pregnancy rate at Glasgow Royal Infirmary's (GRI) Assisted Conception Unit, prompting the health board to transfer infertile couples to the city's private Nuffield hospital for treatment.

The health board said its conception rate had halved to around 15%. Couples struggling to conceive are allowed a maximum of three cycles of IVF on the NHS, with about 30% of women becoming pregnant per cycle.

While clinical error has been ruled out, it is thought building works on the floor above the unit may have led to contamination in the laboratories where embryos are prepared for implant.

Drew Smith, Labour MSP for Glasgow, called on the health board to ensure no couple missed out on their chance to become parents due to the recent glitch.

He said: "I am asking that those couples who have been affected receive at least an additional free cycle, but if other eggs and embryos are damaged, they are allowed to start again.

"Couples going through infertility treatment experience enough distress without now thinking that building work may have destroyed their dreams."

One expert said similar cases in the past would suggest air vents contaminated with toxic fumes and particles from the upstairs building works, where clinical laboratories are being refurbished, may be to blame.

Professor Richard Fleming, a specialist in reproductive medicine and director of the Glasgow Centre for Reproductive Medicine, a private IVF unit, said: "I think the likeliest explanation here is that the ventilation shafts into the fertilisation laboratories have become contaminated by dust or fumes from the building works above."

The GRI conception unit caters for women and couples from NHS Greater Glasgow and Clyde, NHS Lanarkshire, NHS Ayrshire and Arran and NHS Dumfries and Galloway. Around 25 NHS patients a week are now receiving IVF at the Nuffield.

Dr Helen Lyall, consultant gynaecologist at the Assisted Conception Service, said: "Those patients who exhibited reduced or no fertilisation during the period when our pregnancy rates were reduced will all be contacted and offered a complimentary cycle of treatment.

"Clearly many patients who have read the media coverage are concerned their treatment may have been affected. We would like to make it clear the period of concern is for treatment occurring over a defined period only – from September 1 to November 9.

"We wish to reassure patients that outwith this time period there was absolutely no cause for concern."

l An IVF birth more than doubles the likelihood of a child developing asthma, research suggests.

Children conceived with artificial help are also more likely to wheeze or take anti-asthmatic medicines by the age of five.

The UK Millennium Cohort Study compared children in different groups with those born after natural planned pregnancies. Children born to sub-fertile parents were 39% more likely to be experiencing asthma symptoms by the age of five and 27% more likely to wheeze.