Cannabis use during pregnancy alters placental blood vessel markers and increases risk of pregnancy complications | Research

The takeaway

In a study of 8,008 pregnant women, cannabis use before and during pregnancy was associated with altered placental angiogenic markers, higher placental-to-birth-weight ratio, and increased risk of pregnancy complications.

Obstetricians, midwives, pregnant individuals, and researchers studying prenatal substance exposure.

Cannabis use altered placental markers across all three trimesters

What the researchers found

Cannabis use before and during pregnancy was associated with higher PlGF and lower sFlt-1/PlGF ratio in first and second trimesters. First-trimester-only cannabis use was associated with higher sFlt-1 and higher sFlt-1/PlGF ratio at delivery. Continued cannabis or tobacco use was linked to higher placental weight-to-birth-weight ratio and increased pregnancy complications.

Why it matters

This is one of the largest studies to measure specific placental biomarkers in relation to cannabis use, providing mechanistic evidence for how cannabis may lead to adverse pregnancy outcomes.

The numbers in context

8,008 pregnant women. Cannabis use associated with higher PlGF and lower sFlt-1/PlGF ratio (both p<0.05). Continued use linked to higher placental weight-to-birth-weight ratio and more pregnancy complications (both p<0.05).

How the study worked

Population-based prospective cohort of 8,008 pregnant women. Tobacco and cannabis use assessed by questionnaires. Placental growth factor (PlGF) and soluble fms-like tyrosine kinase-1 (sFlt-1) measured in first trimester, second trimester, and at delivery from blood samples. Placental weight and complications from medical records.

What this study cannot tell us

Self-reported substance use likely underestimates true exposure. Cannot fully separate cannabis effects from tobacco (many co-use). Questionnaire-based assessment cannot capture dose or potency. Residual confounding possible.

How to read the evidence

Large population-based prospective cohort with biomarker measurements, though self-reported exposure and potential confounding are limitations.

When this study was published

Published in 2022.

The bigger picture

The finding that cannabis and tobacco both alter placental angiogenic factors, but in somewhat different patterns, suggests these substances affect placental development through overlapping but distinct mechanisms.

Questions still open

Do the altered angiogenic markers explain the increased complication risk, or are they simply correlates? Is there a safe timing or amount of cannabis use during pregnancy? Would the effects differ with CBD-only products?

Common questions

How does cannabis affect the placenta?

This study found cannabis use altered levels of PlGF and sFlt-1, proteins involved in placental blood vessel development. These changes were associated with a higher placental-to-birth-weight ratio and increased pregnancy complications.

Does the timing of cannabis use matter during pregnancy?

Yes. Continued use throughout pregnancy showed different marker patterns than first-trimester-only use, and continued use was associated with more complications. However, even first-trimester-only use showed altered markers at delivery.

Read the original research

Maternal preconception and pregnancy tobacco and cannabis use in relation to placental developmental markers: A population-based study.

Reproductive toxicology (Elmsford, N.Y.), 110, 70-77

View on PubMed ↗Publisher’s paper ↗

Citation

Cajachagua-Torres, Kim N; El Marroun, Hanan; Reiss, Irwin K M; Jaddoe, Vincent W V. (2022). Maternal preconception and pregnancy tobacco and cannabis use in relation to placental developmental markers: A population-based study.. Reproductive toxicology (Elmsford, N.Y.), 110, 70-77. https://doi.org/10.1016/j.reprotox.2022.03.015