What research says about marijuana use during pregnancy
Available evidence suggests prenatal marijuana exposure is associated with fetal growth restriction and adverse neurodevelopmental effects, but most studies were conducted when THC levels were lower and are confounded by other substance use.
Quick Facts
What This Study Found
THC readily crosses the placenta, and cannabinoid receptors have been identified in fetal brain and placenta. Available studies support some degree of developmental disruption, including increased risk of fetal growth restriction and adverse neurodevelopmental consequences. However, most research was done in the 1980s with lower-THC cannabis, relied on self-report, and was confounded by polysubstance use.
Key Numbers
No specific pooled statistics. Review notes marijuana is the most commonly used dependent substance in pregnancy and that much research dates to the 1980s.
How They Did This
Literature review of PubMed-indexed studies on cannabis, cannabinoids, and marijuana in relation to fetal outcomes, perinatal outcomes, pregnancy, and lactation.
Why This Research Matters
Cannabis is the most commonly used dependent substance in pregnancy, and THC concentrations have increased dramatically since the older studies were conducted, making updated research critical.
The Bigger Picture
The gap between today's high-potency products and the lower-THC cannabis studied decades ago means current risk may be higher than older studies suggest, but we lack modern data to confirm this.
What This Study Doesn't Tell Us
Most underlying studies are observational or retrospective with small samples. Self-reported use. Confounded by polysubstance abuse. Older studies used lower-THC cannabis.
Questions This Raises
- ?What are the effects of modern high-potency cannabis on fetal development?
- ?Are there safe consumption levels or windows during pregnancy?
Trust & Context
- Key Stat:
- Most commonly used dependent substance in pregnancy
- Evidence Grade:
- Narrative review of primarily observational studies with significant confounders and outdated THC exposure levels.
- Study Age:
- 2019 review, noting most underlying studies are from the 1980s.
- Original Title:
- Marijuana Use in Pregnancy: A Review.
- Published In:
- Obstetrical & gynecological survey, 74(7), 415-428 (2019)
- Authors:
- Thompson, Rebecca, DeJong, Katherine, Lo, Jamie
- Database ID:
- RTHC-02318
Evidence Hierarchy
Summarizes existing research on a topic.
What do these levels mean? →Frequently Asked Questions
Does marijuana use during pregnancy harm the baby?
Available evidence suggests associations with fetal growth restriction and neurodevelopmental effects, but most studies used lower-potency cannabis and were confounded by other substance use.
Does THC reach the fetus?
Yes. THC readily crosses the placenta, and cannabinoid receptors have been identified in both fetal brain tissue and the placenta.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-02318APA
Thompson, Rebecca; DeJong, Katherine; Lo, Jamie. (2019). Marijuana Use in Pregnancy: A Review.. Obstetrical & gynecological survey, 74(7), 415-428. https://doi.org/10.1097/OGX.0000000000000685
MLA
Thompson, Rebecca, et al. "Marijuana Use in Pregnancy: A Review.." Obstetrical & gynecological survey, 2019. https://doi.org/10.1097/OGX.0000000000000685
RethinkTHC
RethinkTHC Research Database. "Marijuana Use in Pregnancy: A Review." RTHC-02318. Retrieved from https://rethinkthc.com/research/thompson-2019-marijuana-use-in-pregnancy
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.