Pregnant women who smoke are more likely to quit if they are offered shopping vouchers, according to a study.

Researchers studied 612 women over 16 and less than 24 weeks' pregnant to assess whether financial incentives would help them quit the habit.

The study, published in the British Medical Journal, suggested up to 5,000 miscarriages a year could be attributed to smoking during pregnancy, along with hundreds of stillbirths and infant deaths.

Academics estimated the annual cost to the NHS was up to £64m for treating smoking-related problems in mothers and up to £23.5m for the babies up to 12 months old, meaning financial incentives were "potentially cost effective".

Split into two random groups, one set was offered normal stop-smoking services provided by the NHS, while the other group was given the same support and up to £400 in online shopping vouchers for stopping during their pregnancy.

Those in the latter group who agreed to a face-to-face appointment and set a date by which to quit were given an initial £50 voucher before being given further vouchers of £50, £100 and £200 if they managed to abstain from smoking for up to 38 weeks after the set date. Those who said they had quit were tested by a nurse and rewarded only if they were proved to have stopped.

Overall, 23% of smokers offered the vouchers had stopped smoking compared with 9% of others.

But, while the researchers acknowledged there could be ethical issues with offering financial incentives, they said they could prevent smoking-related conditions in mothers and babies and reduce infant mortality.

The report's authors at Glasgow University and the University of Stirling, concluded: "Smoking in pregnancy remains a leading preventable cause of maternal and neonatal ill health and death in the United Kingdom and in most other developed countries.

"Existing interventions are not highly effective. This study provides substantial evidence of a promising and potentially cost effective new intervention to add to present health service support. The findings can serve as the basis for future research to include other UK centres and other healthcare systems."