Cox B ,Martens E ,Nemery B ,Vangronsveld J ,Nawrot TS. Impact of a stepwise introduction of smoke-free legislation on the rate of preterm births: analysis of routinely collected birth data. BMJ 2013;346:f441
- OPEN ACCESS: All research articles are freely available online, with no word limit. Find out more about the BMJ's open access policy. Submit your paper.
- Find out how study types differ in our How to read a paper section.
- Impact factor latest: The BMJ's impact factor is now 17.215. Submit your paper to the world's fourth most cited general medical journal.
- Browse BMJ Open's collection of research papers on global health