Cannabis Use During Pregnancy Disrupted Blood Vessel Function in the Placenta

The study found three distinct patterns: (1) In healthy pregnancies, anandamide relaxed placental arteries via CB1 and CB2 receptors. (2) In preeclampsia, endocannabinoid signaling was altered (lower 2-AG synthesis enzyme) but vessel relaxation was maintained through non-cannabinoid receptor pathways. (3) In cannabis users, endocannabinoid-mediated vessel relaxation was entirely absent, and nitric oxide (NO) signaling was greatly reduced. This provides a mechanistic explanation for why cannabis use during pregnancy is associated with preeclampsia and other vascular complications.

Placental biopsies from gestational age-matched healthy pregnant women, women with preeclampsia, and women who used cannabis throughout pregnancy. Measured ECS component mRNA levels, then tested vascular reactivity of chorionic plate arteries with endogenous and synthetic cannabinoid receptor agonists, with and without selective antagonists.

This is the first study to show that cannabis use during pregnancy fundamentally disrupts both the placental endocannabinoid system and nitric oxide signaling in placental blood vessels. These are two critical systems for maintaining healthy placental blood flow.

The finding that cannabis use eliminates the placenta's ability to respond to its own endocannabinoid system provides direct biological evidence against cannabis use during pregnancy, beyond the epidemiological associations already documented.

Small sample sizes typical of placental tissue studies. Cannot determine whether vascular changes are from THC, CBD, other cannabinoids, or smoking. Cross-sectional tissue analysis cannot assess when changes occurred during pregnancy. Cannabis-using group may differ from non-users in other ways.