A meta-analysis of 13 studies found that fetal cannabis exposure was associated with 79% higher odds of being small for gestational age and 38% higher odds of low birth weight.
Pregnant individuals, prenatal care providers, maternal-fetal medicine specialists
79% higher odds of being small for gestational age
What the researchers found
Neonates with fetal cannabis exposure had significantly higher odds of being small for gestational age (OR=1.79) and low birth weight (OR=1.38). Results for NICU admission (OR=1.38) and preterm birth (OR=1.29) were not statistically significant, though the upper confidence bounds suggest possible clinical relevance.
Why it matters
This meta-analysis pools evidence from multiple studies to provide a clearer picture of prenatal cannabis risks. The significant findings for birth size outcomes add confidence to what individual studies have suggested.
The numbers in context
Small for gestational age: OR=1.79 (95% CI: 1.24-2.59). Low birth weight: OR=1.38 (95% CI: 1.05-1.89). NICU admission: OR=1.38 (95% CI: 0.86-2.22, not significant). Preterm birth: OR=1.29 (95% CI: 0.97-1.71, not significant). 13 studies included from 3,390 identified.
How the study worked
Systematic review and meta-analysis searching five databases. Thirteen studies met inclusion criteria after quality assessment using the Newcastle-Ottawa Scale. Pooled odds ratios were calculated using the Mantel-Haenszel method for dichotomous data.
What this study cannot tell us
Based on 13 studies with varying definitions of cannabis exposure. Could not account for dose, frequency, route, or timing of use. Many included studies relied on self-reported cannabis use, which likely underestimates exposure.
How to read the evidence
Strong: systematic review and meta-analysis pooling 13 studies with quality assessment, providing the highest level of observational evidence
When this study was published
Published in 2025
The bigger picture
The consistent signal for reduced birth size across pooled studies strengthens the case that prenatal cannabis exposure affects fetal growth. The non-significant but potentially clinically relevant findings for preterm birth and NICU admission warrant further research.
Questions still open
- Does the route of cannabis consumption (smoking vs. edibles) affect neonatal outcomes differently? Is there a dose threshold below which fetal growth effects are negligible?
Common questions
How much does prenatal cannabis increase the risk of a small baby?
Does prenatal cannabis cause preterm birth?
Read the original research
Fetal Cannabis Exposure and Neonatal Outcomes: A Systematic Review and Meta-Analysis.
Maternal and child health journal, 29(5), 703-713
Citation
Bailey, Anna; Kerr, Whitney; Alhay, Zahra; Rom, Morgan; Hamilton, Sheryl; Campbell, Janis; Kuhn, Katrin; Thompson, David; Reese, Jessica A. (2025). Fetal Cannabis Exposure and Neonatal Outcomes: A Systematic Review and Meta-Analysis.. Maternal and child health journal, 29(5), 703-713. https://doi.org/10.1007/s10995-025-04096-5
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