Prenatal Cannabis Linked to Preterm Birth, Low Birth Weight, and NICU Stays

Intrauterine cannabis exposure was associated with preterm delivery (OR=1.68, p=0.03), low birth weight (OR=2.60, p<0.001), and NICU admission (OR=2.51, p<0.001). Qualitative synthesis found associations with poorer attention and externalizing problems in early childhood, but no evidence for impairments in other cognitive domains or internalizing behaviors.

Systematic review and meta-analysis following PRISMA guidelines. Searched PubMed and PsycINFO from database inception through June 2023. 932 studies screened, 57 met eligibility criteria. Included prospective and cross-sectional human studies measuring birth, behavioral, psychological, and cognitive outcomes.

This is the most comprehensive meta-analysis to date on prenatal cannabis effects. The birth outcome findings are robust, while the more nuanced cognitive finding (limited to attention/externalizing) pushes back against overly broad claims of developmental harm.

The finding that birth outcomes are clearly affected while early childhood cognition is largely spared (except attention) suggests that cannabis may have its greatest impact on fetal growth rather than brain development per se, though longer follow-up studies are needed.

Many included studies could not fully control for concurrent tobacco use, socioeconomic factors, or other substance exposure. Self-reported cannabis use likely underestimates exposure. The cognitive literature is qualitatively synthesized due to heterogeneity, limiting the strength of those conclusions.