A comprehensive review finds that cannabis use disrupts the placental endocannabinoid system, impairing placental development and blood flow, with epidemiological evidence linking use to fetal growth restriction, preeclampsia, and potential transgenerational effects through DNA methylation changes.
Pregnant individuals, obstetricians, midwives, perinatal researchers, and public health professionals developing pregnancy guidelines.
What the researchers found
Cannabis use interferes with the placental endocannabinoid system which regulates placental development and blood flow, with THC and CBD exerting effects via this system — and epidemiological data linking cannabis use to placental insufficiency, fetal growth restriction, preeclampsia, and potential epigenetic transgenerational effects.
Why it matters
With cannabis use during pregnancy increasing alongside legalization and perceived safety, this review compiles the growing evidence that cannabis directly interferes with placental function through a specific biological system.
The numbers in context
Reviews evidence on both maternal and paternal cannabis use effects; covers THC and CBD; documents links to fetal growth restriction, preeclampsia, placental insufficiency; highlights DNA methylation changes as transgenerational risk
How the study worked
Comprehensive narrative review synthesizing evidence on the placental endocannabinoid system, THC/CBD effects on placental function, cannabinoid pharmacokinetics during pregnancy, epidemiological data on birth outcomes, and emerging epigenetic evidence.
What this study cannot tell us
Narrative review with potential selection bias; many included studies are preclinical; epidemiological data on pregnancy outcomes often has confounders (tobacco, alcohol co-use); epigenetic evidence is early-stage; dose-response relationships poorly characterized.
How to read the evidence
Thorough narrative review integrating molecular, clinical, and epidemiological evidence, but relies partly on preclinical data and observational studies with potential confounding.
When this study was published
Published 2026; reviews the latest evidence including post-legalization epidemiological data.
The bigger picture
The presence of a functional endocannabinoid system in the placenta means that cannabis isn't just passing through — it's actively interfering with the biological machinery that supports fetal growth and development.
Questions still open
- Is there a safe level of cannabis use during pregnancy? How do different consumption methods (smoking vs. edibles vs. topicals) affect placental exposure? Could the epigenetic effects truly span generations?
Common questions
Is it safe to use cannabis during pregnancy?
Can a father's cannabis use affect the baby?
Read the original research
Recreational Cannabis Use During Human Pregnancy: Its Effects on the Placenta and Endocannabinoid System.
International journal of molecular sciences, 27(3)
Citation
Harhangi, Madhavi S; Höfert, Lisa; Danser, A H Jan; Bijma, Hilmar H; Simons, Sinno H P; Reiss, Irwin K M; Baumann, Sven; Broekhuizen, Michelle. (2026). Recreational Cannabis Use During Human Pregnancy: Its Effects on the Placenta and Endocannabinoid System.. International journal of molecular sciences, 27(3). https://doi.org/10.3390/ijms27031398
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