Concurrent drinking and smoking during pregnancy is a major public health concern. Changes in these behaviours are under-researched, although essential if effective interventions are to be implemented. Hence this paper investigated characteristics of women who decreased concurrent drinking and smoking during pregnancy. 1,591 women were identified as pregnant at one of three surveys from 2000 to 2006 of the Australian Longitudinal Study on Women's Health and not pregnant at the previous survey. Relative risks (RRs) were calculated for concurrent drinkers and smokers before pregnancy of (1) decreasing drinking, (2) decreasing smoking and (3) decreasing drinking and smoking during pregnancy. Three hundred and fifty-four women (22%) were concurrent drinkers and smokers before pregnancy; of these women, 73% decreased drinking, 72% decreased smoking and 53% decreased drinking and smoking during pregnancy. Decreased concurrent drinking and smoking was significantly higher among women who had at least 12 years education (RRs: 1.5-1.6), who drank at least 1-2 days/week (RRs: 1.5-1.6) and who had 3 or more drinks per occasion (RRs: 1.6-1.8), and significantly lower among heavy smokers, mothers of other children (RRs: 0.8) and disadvantaged women: those stressed about money, with poor mental health, low social support and experience of partner violence (RRs: 0.6-0.7). Clearly programs are needed to tackle concurrent drinking and smoking during pregnancy. Given many pregnancies are unplanned, these programs should target drinking and smoking before and during pregnancy, as well as disadvantaged women, to reduce the deleterious effects of concurrent substance use on their babies and themselves. © Springer Science+Business Media, LLC 2012.