Pregnancy-related changes in tobacco, alcohol and cannabis use reported by antenatal patients at two public hospitals in South Australia

Background: Australian substance use data do not demonstrate pregnancy-related changes or distinguish between pregnant and lactating women.
Aims: To determine such changes by antenatal patients at two South Australian public hospitals accounting for 35% of the state's births.
Methods: In 2005–2006, all first visit antenatal women at the two hospitals were asked by clinic staff to complete an anonymous, self-administered questionnaire prompting details of substance use, current and previous (while not pregnant or lactating).
Results: Questionnaires were returned by 748 women, 34.4% of 2173 eligible in the study period. Women reported use at significantly lower rates than before pregnancy. Tobacco was most used in pregnancy (18.5%), followed by alcohol (11.8%) and cannabis (4.5%), with negligible use of other illicit substances. There was no significant difference in substance use related to trimester. Women with previous pregnancy losses were significantly more likely to use tobacco and alcohol. Younger women were more likely to use tobacco and cannabis, with no age-related differences in alcohol consumption. First pregnancy was the only factor independently associated with the likelihood of ceasing substance use when pregnant, but only in relation to alcohol.
Conclusions: Women were less likely to use all substances when pregnant, and health-care providers should reinforce and support these decisions. The use of cannabis and alcohol while pregnant was below expectations. Reported tobacco use was concordant with existing data and confirms that the risk of smoking in pregnancy remains a message difficult to communicate in the context of chronic nicotine dependence.