Fetal THC Exposure Rose After Illinois Legalized Cannabis
Umbilical cord THC positivity rates increased from 40.6% to 46.2% after Illinois legalized recreational cannabis, with significantly higher THC concentrations in positive samples.
Quick Facts
What This Study Found
A higher percentage of umbilical cord tissue tested positive for THC after legalization (46.2% vs. 40.6%, p<0.05) and THC concentrations were significantly higher in the post-legalization period (p<0.001). This suggests both more fetuses were exposed and those exposed experienced higher levels.
Key Numbers
811 cords pre-legalization, 2,170 post-legalization. THC positivity: 40.6% vs. 46.2% (p<0.05). THC concentration: significantly higher post-legalization (p<0.001).
How They Did This
Retrospective observational study at a single center comparing umbilical cord tissue THC levels before (Epoch 1: Oct 2018-Jun 2019, n=811) and after (Epoch 2: Jul 2019-Aug 2021, n=2,170) cannabis legalization in Illinois.
Why This Research Matters
Umbilical cord tissue provides an objective measure of fetal THC exposure, avoiding the limitations of self-report. This is direct evidence that legalization was associated with increased fetal cannabis exposure.
The Bigger Picture
The finding that over 40% of cord tissues tested positive for THC even before legalization is itself striking, suggesting prenatal cannabis exposure was already common. Legalization appears to have increased both the prevalence and intensity of exposure.
What This Study Doesn't Tell Us
Single center, limiting generalizability. Cannot determine timing, frequency, or mode of cannabis use. THC in cord tissue reflects exposure but not necessarily fetal effects. Pre/post comparison cannot account for secular trends. No clinical outcome data for exposed newborns.
Questions This Raises
- ?What are the clinical outcomes for newborns with higher cord THC concentrations?
- ?Does the route of cannabis consumption (smoking vs. edibles) affect cord THC levels differently?
Trust & Context
- Key Stat:
- Evidence Grade:
- Objective biological measure from a large sample, but single-center design and inability to assess clinical outcomes limit to moderate.
- Study Age:
- Data from October 2018 through August 2021, spanning Illinois legalization.
- Original Title:
- Impact of Cannabis Legalization on Umbilical Cord Tissue Tetrahydrocannabinol Levels.
- Published In:
- American journal of perinatology, 42(9), 1206-1212 (2025)
- Database ID:
- RTHC-07706
Evidence Hierarchy
Watches what happens naturally without intervening.
What do these levels mean? →Frequently Asked Questions
Did legalization lead to more prenatal cannabis use?
This study found higher THC positivity rates and concentrations in umbilical cord tissue after legalization, suggesting increased fetal exposure, though the study cannot determine whether more women used cannabis or if existing users used more.
Is THC in umbilical cord tissue harmful?
This study measured exposure only, not outcomes. Other research suggests prenatal THC exposure may affect fetal development, but this study did not assess newborn health outcomes.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-07706APA
Spence, Kimberly; Milota, Sarah; Buchanan, Paula; Acharya, Nirja; Mathur, Amit M. (2025). Impact of Cannabis Legalization on Umbilical Cord Tissue Tetrahydrocannabinol Levels.. American journal of perinatology, 42(9), 1206-1212. https://doi.org/10.1055/a-2480-3163
MLA
Spence, Kimberly, et al. "Impact of Cannabis Legalization on Umbilical Cord Tissue Tetrahydrocannabinol Levels.." American journal of perinatology, 2025. https://doi.org/10.1055/a-2480-3163
RethinkTHC
RethinkTHC Research Database. "Impact of Cannabis Legalization on Umbilical Cord Tissue Tet..." RTHC-07706. Retrieved from https://rethinkthc.com/research/spence-2025-impact-of-cannabis-legalization
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.