Mothers in Scotland's biggest city are being offered up to £400 to quit smoking during pregnancy.

The Glasgow trial scheme aims to find out whether financial incentives, such as the £50 in-store vouchers that will be offered, can help more women kick the habit.

Participants will receive the first voucher when they book their first face-to-face appointment with an NHS smoking cessation adviser and set a date to stop.

If they remain smoke-free for four weeks, with tests being carried out on their breath for signs of carbon monoxide contained in cigarette smoke, they will receive a further £50 of vouchers, rising to £100 at 12 weeks. They will get

£200 worth of vouchers if they reach eights months, when they will be asked to submit saliva and urine samples to prove there is no trace of cigarettes in their system.

The trial has recruited 64 pregnant women from within the NHS Greater Glasgow and Clyde region since the end of December and aims to recruit a total of 600 by the end of the year, with all expectant mothers using the health board's Smoke-Free service automatically invited to take part.

The study will be split equally between women receiving the financial incentives to stop and a control group receiving normal smoking cessation support plus a £25 bonus at the end to thank them for participating.

The trial is spearheaded by Professor Linda Bauld, of Stirling University, and Professor David Tappin, of Glasgow University, on behalf of the UK Centre for Tobacco Control, with £750,000 of funding from Scotland's Chief Scientist Office, the Glasgow Centre for Population Health, and research bequests.

Although NHS Tayside launched a pharmacy-based pilot study in 2010 offering smokers £12.50 a week in shopping vouchers to quit during pregnancy, the Glasgow trial will be the first study in the UK to test the benefits of financial incentives against a control group.

Researchers would expect to see a 10%-15% improvement in cessation rates among the incentive group to support the case for financial rewards, something already suggested in US studies.

Ms Bauld said: "About a third of women will stop right away – through willpower, nicotine replacement therapy, whatever, they can do it. But then there's another very large group of smokers who are heavily addicted and maybe live in circumstances where they depend on smoking, their friends and family smoke, and it's very difficult for them to stop.

"So when you look at the evidence, we have very little to offer these people.

Glasgow has the highest rates of smoking during pregnancy in Scotland, with one in every four expectant mothers lighting up.

It is believed to account for around half of all cot deaths in Scotland, around a quarter of miscarriages and stillbirths, and reduces birthweight by an average of 10%.