Prenatal Cannabis Linked to Multiple Types of Birth Defects in Large Meta-Analysis

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.

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.

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.

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.

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.