Study Warns of CBD’s Impact on Fetal Growth

CBD use during pregnancy may impair fetal growth and development, warns a new McMaster University study.

A new study at McMaster University has raised an alarm about the potential risks of using cannabidiol (CBD) when pregnant. Despite CBD being generally used to address symptoms like nausea, anxiety, and sleep disorder, scientists have found that its use through ingestion from early through mid-pregnancy can lead to impaired fetal development and alterations in growth.

The study, which was recently released in the journal eBioMedicine on February 5, 2025, showed that both CBD and THC influence the development of the placenta and blood vessels that supply nutrition to the child. As such, fetuses exposed to such cannabis compounds were found to be lighter at birth compared to fetuses that did not receive this exposure.

Researchers also noted that CBD and THC disrupted a special type of immune cell, uterine NK cells, which are crucial for the normal development of the placenta. Poorly developed arteries that supply the placenta can compromise nutrient and oxygen delivery to the fetus, resulting in growth restriction.

Other than fetal development, studies also found that prenatal cannabis exposure led to behavioral changes of offspring. Exposure to CBD and THC during pregnancy had mice with increased aggression, activity level differences, and possible learning impairment when they matured.

Use of marijuana by pregnant women is increasing, particularly in Canada, while much of the earlier research was focused on THC and marijuana smoke.  While further research is needed to determine these findings in humans, the research points out possible risks with prenatal use of cannabis.  Pregnant patients are encouraged to discuss with medical professionals prior to using CBD or cannabis products to ensure optimal maternal and fetal health.