The prevalence and significance of gestational cannabis use at an Australian tertiary hospital

Background: Cannabis is one of the most common non-prescribed psychoactive substances used in pregnancy. The prevalence of gestational cannabis use is increasing. Aim: The aim was to examine the prevalence of gestational cannabis use and associated pregnancy and neonate outcomes. Materials and Methods: A retrospective observational study involving pregnant women delivering in 2019 was conducted at a tertiary hospital in Perth, Western Australia. Gestational cannabis and other substance use records were based on maternal self-report. Pregnancy outcomes included neonatal gestational age, birthweight, birth length, head circumference, resuscitation measures, special care nursery admission, 5-min Apgar score and initial neonatal feeding method. Results: Among 3104 pregnant women (mean age: 31 years), gestational cannabis use was reported by 1.6% (n = 50). Cannabis users were younger, more likely to use other substances and experience mental illness or domestic violence compared with non-users. Neonates born to cannabis users had a lower mean gestational age, birthweight and birth length compared to those born to non-cannabis users. Gestational cannabis use (odds ratio (OR) 3.3, 95% confidence interval (CI) 1.6–6.7) and tobacco smoking (OR 2.2, 95% CI 1.5–3.6) were associated with increased odds of a low-birthweight neonate. Combined cannabis and tobacco use during pregnancy further increased the likelihood of low birthweight (LBW, adjusted OR 3.9, 95% CI 1.6–9.3). Multivariate logistic regression analysis adjusted for maternal socio-demographical characteristics, mental illness, alcohol, tobacco and other substance use demonstrated gestational cannabis use to be independently associated with LBW (OR 2.3, 95% CI 1.1–5.2). Conclusion: Gestational cannabis use was independently associated with low birthweight, synergistically affected by tobacco smoking