Cannabis Use During Pregnancy Was Linked to Smaller Babies
In a Michigan pregnancy cohort, about 15% of participants used cannabis during pregnancy, and prenatal cannabis exposure was associated with smaller birth size after adjusting for other factors.
Quick Facts
What This Study Found
Covariate-adjusted models revealed a significant association between prenatal cannabis exposure and reduced birth size (β = -0.3; 95% CI: -0.5, -0.003), using a continuous birth size measure rather than just birth weight extremes.
Key Numbers
15% of participants reported cannabis use during pregnancy (95% CI: 12%–18%). Birth size association: β = -0.3 (95% CI: -0.5, -0.003). Sample: 584 participants from 23 Michigan clinics, recruited 2017–2022.
How They Did This
Prospective pregnancy cohort from the Michigan Archive for Research on Child Health linking prenatal survey data with birth records from 23 clinics (n=584). Generalized linear models adjusted for covariates including tobacco and alcohol use.
Why This Research Matters
With cannabis use during pregnancy increasing as legalization expands and risk perception decreases, understanding the effects on fetal development is critical for prenatal counseling and clinical guidelines.
The Bigger Picture
This study adds to evidence that prenatal cannabis exposure may affect fetal growth. Notably, it used a continuous birth size measure rather than just looking at extremes like low birth weight, potentially capturing subtler effects that previous studies missed.
What This Study Doesn't Tell Us
Moderate sample size (n=584). Cannabis use was self-reported, which may underestimate prevalence. Cannot isolate THC from other cannabis compounds. Observational design cannot prove causation. Single state (Michigan).
Questions This Raises
- ?What specific aspect of birth size is most affected — weight, length, or head circumference?
- ?Does the timing or frequency of cannabis use during pregnancy matter?
- ?Are effects mediated by THC crossing the placenta?
Trust & Context
- Key Stat:
- Evidence Grade:
- Prospective cohort design with covariate adjustment, but moderate sample size and self-reported exposure measurement.
- Study Age:
- Published 2025, data from 2017–2022.
- Original Title:
- Estimating the effects of prenatal cannabis exposure on birth outcomes.
- Published In:
- The American journal on addictions, 34(1), 21-29 (2025)
- Authors:
- Vanderziel, Alyssa(5), Anthony, James C(4), Barondess, David(2), Kerver, Jean M, Alshaarawy, Omayma
- Database ID:
- RTHC-07854
Evidence Hierarchy
Frequently Asked Questions
How much smaller were babies exposed to cannabis?
The study found a statistically significant but modest reduction in overall birth size (β = -0.3). The effect was measured as a composite birth size score rather than specific grams of weight difference.
Is occasional cannabis use during pregnancy safe?
This study did not distinguish between frequency levels. Major medical organizations including ACOG recommend avoiding cannabis entirely during pregnancy, as THC crosses the placenta and interacts with fetal cannabinoid receptors.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-07854APA
Vanderziel, Alyssa; Anthony, James C; Barondess, David; Kerver, Jean M; Alshaarawy, Omayma. (2025). Estimating the effects of prenatal cannabis exposure on birth outcomes.. The American journal on addictions, 34(1), 21-29. https://doi.org/10.1111/ajad.13650
MLA
Vanderziel, Alyssa, et al. "Estimating the effects of prenatal cannabis exposure on birth outcomes.." The American journal on addictions, 2025. https://doi.org/10.1111/ajad.13650
RethinkTHC
RethinkTHC Research Database. "Estimating the effects of prenatal cannabis exposure on birt..." RTHC-07854. Retrieved from https://rethinkthc.com/research/vanderziel-2025-estimating-the-effects-of
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.