A cumulative meta-analysis of 36 studies covering over 18 million births found prenatal cannabis exposure associated with 2-3x higher risks of cardiovascular, gastrointestinal, central nervous system, and genitourinary birth defects.
Obstetricians, genetic counselors, and pregnant individuals
2.87x higher risk of central nervous system birth defects
What the researchers found
Prenatal cannabis exposure was associated with increased risks of cardiovascular/heart defects (OR=2.35), gastrointestinal defects (OR=2.42), central nervous system defects (OR=2.87), genitourinary defects (OR=2.39), and any/unclassified birth defects (OR=1.25). All associations were statistically significant.
Why it matters
This is the most comprehensive meta-analysis to date linking prenatal cannabis to specific types of structural birth defects. The consistent 2-3x risk increases across multiple organ systems suggests a broad teratogenic effect rather than a system-specific one.
The numbers in context
36 studies, 230,816 birth defect cases, 18,049,013 controls. Cardiovascular: OR=2.35 (CI: 1.63-3.39). Gastrointestinal: OR=2.42 (CI: 1.61-3.64). CNS: OR=2.87 (CI: 1.51-5.46). Genitourinary: OR=2.39 (CI: 1.11-5.17). Any defects: OR=1.25 (CI: 1.12-1.41).
How the study worked
Cumulative meta-analysis following a preregistered PROSPERO protocol. Searched seven databases through January 2024. Included 36 observational studies (18 case-control, 18 cohort) with 230,816 birth defect cases and 18,049,013 controls. Methodological quality assessed via Newcastle-Ottawa Scale. Subgroup, leave-one-out, and meta-regression analyses performed.
What this study cannot tell us
Observational studies cannot prove causation. Cannabis use is typically self-reported and likely underestimated. Concurrent substance use (especially tobacco) is difficult to fully disentangle. Different studies measured cannabis exposure in different ways.
How to read the evidence
Large preregistered meta-analysis with robust sensitivity analyses, though underlying observational studies have inherent limitations.
When this study was published
2024 cumulative meta-analysis
The bigger picture
As cannabis legalization spreads and prenatal use increases, the birth defect findings add urgency to preconception counseling. The broad pattern of defects across multiple organ systems is consistent with cannabis crossing the placenta and affecting early organogenesis.
Questions still open
- Is there a dose-response relationship? Are certain gestational windows more vulnerable? Would studies using biomarker-confirmed exposure show even stronger associations?
Common questions
Can cannabis use during pregnancy cause birth defects?
Which type of birth defect was most strongly linked to prenatal cannabis?
Read the original research
The association between prenatal cannabis use and congenital birth defects in offspring: A cumulative meta-analysis.
Neurotoxicology and teratology, 102, 107340
Citation
Tadesse, Abay Woday; Ayano, Getinet; Dachew, Berihun Assefa; Tusa, Biruk Shalmeno; Damtie, Yitayish; Betts, Kim; Alati, Rosa. (2024). The association between prenatal cannabis use and congenital birth defects in offspring: A cumulative meta-analysis.. Neurotoxicology and teratology, 102, 107340. https://doi.org/10.1016/j.ntt.2024.107340
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