Prenatal Cannabis Use Linked to Two Rare Abdominal Wall Birth Defects
In a study of nearly 364,000 births, prenatal cannabis use was associated with a nearly 3-fold increased risk of omphalocele, a rare abdominal wall defect, but not with other major birth defects.
Quick Facts
What This Study Found
Maternal prenatal cannabis use was associated with omphalocele (adjusted risk ratio 2.92) after propensity score adjustment. An initial association with gastroschisis did not survive full adjustment. No associations were found between prenatal cannabis use and any of the other 36 birth defects examined.
Key Numbers
363,952 infants studied. 6.2% (22,494) exposed to prenatal cannabis. Omphalocele risk ratio: 2.92 (95% CI: 1.26-6.77) after propensity score adjustment. Both conditions were rare: gastroschisis in 0.05% and omphalocele in 0.01% of births.
How They Did This
Population-based retrospective cohort of 363,952 singleton births from a health system that universally screens for substance use at prenatal care entry. Cannabis exposure was defined by self-report or positive toxicology. Researchers examined 38 specific birth defects across 8 organ systems using modified Poisson regression with propensity score adjustment.
Why This Research Matters
With prenatal cannabis use rising, understanding potential effects on fetal development is critical. This large study with universal screening (reducing detection bias) provides some of the strongest evidence to date on specific birth defect risks.
The Bigger Picture
While the relative risk increase is notable, the absolute risk of omphalocele remains extremely low (0.01% of births). The lack of association with 36 other defects is also informative for risk counseling.
What This Study Doesn't Tell Us
Observational design cannot prove causation. Cannabis exposure was measured at prenatal care entry, not throughout pregnancy. Could not account for potency, frequency, or route of use. Very small number of omphalocele cases (n=48) limits precision.
Questions This Raises
- ?What biological mechanism might explain a specific link to abdominal wall defects?
- ?Does the timing or frequency of cannabis use during pregnancy matter?
Trust & Context
- Key Stat:
- 2.92x increased risk of omphalocele with prenatal cannabis use
- Evidence Grade:
- Moderate: large population-based cohort with universal screening, but observational design and very small case numbers for the defects found
- Study Age:
- Published in 2025 using 2011-2020 birth data
- Original Title:
- Maternal Prenatal Cannabis Use and Major Structural Birth Defects.
- Published In:
- Birth defects research, 117(6), e2492 (2025)
- Authors:
- Avalos, Lyndsay A(13), Adams, Sara R(18), Alexeeff, Stacey E(19), Oberman, Nina R, Does, Monique B, Steuerle, Kristin R, Ansley, Deborah R, Castellanos, Carley L, Padon, Alisa A, Silver, Lynn D, Young-Wolff, Kelly C
- Database ID:
- RTHC-05978
Evidence Hierarchy
Looks back at existing records to find patterns.
What do these levels mean? →Frequently Asked Questions
How common is omphalocele?
Very rare. In this study, omphalocele occurred in 0.01% of births (48 out of 363,952). Even with a roughly 3-fold increased relative risk from cannabis exposure, the absolute risk remains extremely low.
Were other birth defects affected?
No. The study examined 38 specific birth defects across 8 organ systems and found no association between prenatal cannabis use and any defect other than omphalocele (and a weaker signal for gastroschisis that didn't survive full statistical adjustment).
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-05978APA
Avalos, Lyndsay A; Adams, Sara R; Alexeeff, Stacey E; Oberman, Nina R; Does, Monique B; Steuerle, Kristin R; Ansley, Deborah R; Castellanos, Carley L; Padon, Alisa A; Silver, Lynn D; Young-Wolff, Kelly C. (2025). Maternal Prenatal Cannabis Use and Major Structural Birth Defects.. Birth defects research, 117(6), e2492. https://doi.org/10.1002/bdr2.2492
MLA
Avalos, Lyndsay A, et al. "Maternal Prenatal Cannabis Use and Major Structural Birth Defects.." Birth defects research, 2025. https://doi.org/10.1002/bdr2.2492
RethinkTHC
RethinkTHC Research Database. "Maternal Prenatal Cannabis Use and Major Structural Birth De..." RTHC-05978. Retrieved from https://rethinkthc.com/research/avalos-2025-maternal-prenatal-cannabis-use
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.