Smoking in pregnancy is recognised to have major health costs, both for the mother and her child. A higher proportion of women manage to quit by early pregnancy than at other times of their lives; however, around 19% ofwomen in England smoke throughout their pregnancy. While there is some data available on costs to the NHS of adult smokers, there are currently no models which provide these estimates for smoking in pregnancy. The costs and wider economic implications of smoking in pregnancy are gaps identified as a priority need by DH policy teams. This project aims to build an estimate of the additional costs that accrue to society of a mother continuing to smoke during pregnancy compared to the alternatives of a mother giving up smoking during pregnancy. In collaboration with the Public Health Research Consortium, York.