Rhesus monkeys given daily THC edibles from before conception through pregnancy had significantly decreased amniotic fluid, reduced placental blood flow, lower fetal oxygen availability, and placental tissue damage compared to controls.
Obstetricians; maternal-fetal medicine specialists; pregnant women considering cannabis use; reproductive toxicology researchers.
Placental microinfarctions found only in THC-exposed pregnancies
What the researchers found
THC-exposed pregnancies showed significantly decreased amniotic fluid volume (p<0.001), reduced placental perfusion (p<0.05), and lower fetal oxygen availability (p<0.05). Placental tissue showed microinfarctions only in THC-exposed animals. RNA sequencing revealed disrupted blood vessel development and angiogenesis pathways.
Why it matters
This is the first primate study using advanced imaging to demonstrate that THC impairs placental function during pregnancy. The findings of reduced blood flow and oxygen delivery to the fetus have direct implications for human cannabis use during pregnancy.
The numbers in context
10 rhesus macaques (5 THC, 5 control). Imaging at G85, G110, G135, G155. THC group: significantly decreased amniotic fluid (p<0.001), placental perfusion (p<0.05), fetal oxygen availability (p<0.05). Microinfarctions found only in THC-exposed placentas. RNA-seq showed dysregulated vasculature development.
How the study worked
Controlled study in 10 rhesus macaques (5 THC, 5 control). THC group received daily THC edibles pre-conception through pregnancy. Serial ultrasound and MRI at four gestational timepoints. Cesarean delivery at gestational day 155 (near term) with placental collection for histology and RNA sequencing.
What this study cannot tell us
Small sample size (5 per group). Daily THC edible dosing may not reflect all human use patterns. The study ended before natural delivery, so birth outcomes are unknown. A single THC preparation was used, not reflecting the variety of cannabis products.
How to read the evidence
Moderate: controlled primate study with advanced imaging and molecular analysis, though limited by small sample size.
When this study was published
Published in 2022.
The bigger picture
Rhesus macaques share similar placental biology with humans, making these findings particularly relevant. The convergence of reduced blood flow, lower oxygen, tissue damage, and disrupted vascular gene expression creates a compelling picture of placental insufficiency from THC exposure.
Questions still open
- What are the downstream effects on offspring development after birth? Is there a dose threshold below which placental effects do not occur? Would CBD co-exposure modify the THC placental effects?
Common questions
Is it safe to use cannabis during pregnancy?
What is placental insufficiency?
Read the original research
Chronic prenatal delta-9-tetrahydrocannabinol exposure adversely impacts placental function and development in a rhesus macaque model.
Scientific reports, 12(1), 20260
Citation
Roberts, Victoria H J; Schabel, Matthias C; Boniface, Emily R; D'Mello, Rahul J; Morgan, Terry K; Terrobias, Juanito Jose D; Graham, Jason A; Borgelt, Laura M; Grant, Kathleen A; Sullivan, Elinor L; Lo, Jamie O. (2022). Chronic prenatal delta-9-tetrahydrocannabinol exposure adversely impacts placental function and development in a rhesus macaque model.. Scientific reports, 12(1), 20260. https://doi.org/10.1038/s41598-022-24401-4
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