Intended for healthcare professionals

Endgames Statistical Question

What are the risks?

BMJ 2015; 350 doi: (Published 02 June 2015) Cite this as: BMJ 2015;350:h2931
  1. Philip Sedgwick, reader in medical statistics and medical education,
  2. Katherine Joekes, senior lecturer in clinical communication
  1. 1Institute for Medical and Biomedical Education, St George’s, University of London, London, UK
  1. Correspondence to: P Sedgwick p.sedgwick{at}

Researchers investigated the effectiveness of offering financial incentives in helping pregnant smokers to quit. A randomised controlled trial was performed. The intervention consisted of routine care plus incentives of up to £400 (€559; $600) for women who attended specialist pregnancy stop smoking services and were abstinent from smoking at 34-38 weeks’ gestation. The control group received routine care only, which included offers of face to face appointments to discuss smoking and cessation, free nicotine replacement therapy, and weekly support phone calls. The setting was a materially deprived inner city population in the west of Scotland. Participants were 612 self reported pregnant smokers aged at least 16 years who were less than 24 weeks pregnant. Women were randomised to the intervention (n=306) or control (n=306). Consent, including consent to use any data collected, was subsequently withdrawn by three women allocated to the control group, resulting in a sample size of 303 for analysis of the primary outcome.1

The primary outcome was abstinence from smoking at 34-38 weeks’ gestation. The percentage of smokers who were abstinent at 34-38 weeks’ gestation was significantly higher in the financial incentives group than in the control group (22.55% (n=69) v 8.58% (n=26), absolute risk difference 13.97%; relative risk 2.63, 95% confidence interval 1.73 to 4.01; P<0.001). The researchers concluded that financial incentives were effective in helping pregnant smokers quit.

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