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.
Pregnant individuals, people planning pregnancy, and prenatal care providers.
Most commonly used dependent substance in pregnancy
What the researchers 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.
Why it 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 numbers in context
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 the study worked
Literature review of PubMed-indexed studies on cannabis, cannabinoids, and marijuana in relation to fetal outcomes, perinatal outcomes, pregnancy, and lactation.
What this study cannot 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.
How to read the evidence
Narrative review of primarily observational studies with significant confounders and outdated THC exposure levels.
When this study was published
2019 review, noting most underlying studies are from the 1980s.
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.
Questions still open
- What are the effects of modern high-potency cannabis on fetal development? Are there safe consumption levels or windows during pregnancy?
Common questions
Does marijuana use during pregnancy harm the baby?
Does THC reach the fetus?
Read the original research
Marijuana Use in Pregnancy: A Review.
Obstetrical & gynecological survey, 74(7), 415-428
Citation
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
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