A meta-analysis of 57 studies found prenatal cannabis exposure increased the risk of preterm delivery by 68%, low birth weight by 160%, and NICU admission by 151%, with limited evidence of cognitive harm in early childhood beyond attention problems.
Obstetricians, neonatologists, and pregnant individuals
2.6x higher risk of low birth weight with prenatal cannabis exposure
What the researchers found
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.
Why it matters
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 numbers in context
57 studies included. Preterm delivery: OR=1.68 (CI: 1.05-2.71). Low birth weight: OR=2.60 (CI: 1.71-3.94). NICU admission: OR=2.51 (CI: 1.46-4.31). Attention and externalizing problems found in qualitative synthesis. No evidence for other cognitive impairments.
How the study worked
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.
What this study cannot tell us
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.
How to read the evidence
Large meta-analysis with 57 studies and clear dose of evidence for birth outcomes; cognitive findings limited by study heterogeneity.
When this study was published
2024 meta-analysis
The bigger picture
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.
Questions still open
- Are the birth outcome effects driven by smoking as a route of administration rather than cannabis itself? Do attention problems persist into school age and beyond? Would controlling for tobacco use change the birth outcome findings?
Common questions
Does cannabis use during pregnancy affect birth outcomes?
Does prenatal cannabis harm child brain development?
Read the original research
Birth, cognitive and behavioral effects of intrauterine cannabis exposure in infants and children: A systematic review and meta-analysis.
Addiction (Abingdon, England), 119(3), 411-437
Citation
Sorkhou, Maryam; Singla, Daisy R; Castle, David J; George, Tony P. (2024). Birth, cognitive and behavioral effects of intrauterine cannabis exposure in infants and children: A systematic review and meta-analysis.. Addiction (Abingdon, England), 119(3), 411-437. https://doi.org/10.1111/add.16370
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