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Abstract
Up to 10% of women may use cannabis during pregnancy; this is of concern because constituents of cannabis cross the placental barrier and potentially influence neurodevelopment by acting on cannabinoid receptors in the developing fetal brain. In this context, a recent meta analysis of 13 observational studies found that gestational exposure to cannabis was associated with a small increase in the risk of autism spectrum disorder (ASD; relative risk [RR], 1.30) and with an even smaller increase in the risk of attention deficit/hyperactivity disorder (ADHD; RR, 1.13); the latter finding was probably supported by publication bias. In this meta-analysis, 4 studies provided information on ASD (pooled N = 178,565) and 10 on ADHD (pooled N = 203,783). In a large (n = 222,534) retrospectively ascertained cohort study published after the meta-analysis, cannabis use disorder (CUD) recorded before pregnancy, during pregnancy, and during pregnancy plus the year after delivery were associated with closely similar increased risks of ASD (RRs, 3.02–3.21). The risks were smaller in smokers (RRs, 1.74–1.87) than in nonsmokers (RRs, 4.55–4.83) but differed little between male (RRs, 3.01–3.06) and female (RRs, 2.71–2.85) offspring. Although the cohort study had many strengths, its limitations permitted only the conclusion that peri-pregnancy exposure to CUD is associated with a large increase in the risk of ASD in offspring; it remained possible that much of the risk was driven by genetic, environmental, or behavioral variables. The field is nascent; the total number of cannabis exposed pregnancies (with ASD and ADHD as the outcomes) in world literature is small. However, cannabis use during pregnancy is, at the very least, a clear marker for adverse neurodevelopmental outcomes, besides the adverse maternal, fetal, and neonatal outcomes identified in other studies. Healthcare providers who manage women who use cannabis during pregnancy need to be aware of these adverse outcomes.