New Evidence Highlights Risks of Cannabis Use During Pregnancy

A comprehensive systematic review and meta-analysis have raised significant concerns about the use of cannabis during pregnancy. The research, conducted by scientists at Oregon Health & Science University and published in JAMA Pediatrics, suggests that prenatal cannabis exposure is associated with increased risks of adverse neonatal outcomes. These include higher chances of preterm birth, low birth weight, and infants being small for their gestational age. The study analyzed data from 51 observational studies involving over 21 million individuals, incorporating eight new studies into the latest review. The findings indicate a moderate level of evidence linking prenatal cannabis use to these adverse outcomes, and also suggest increased neonatal mortality, though this carries lower certainty.

Cannabis remains one of the most commonly used substances during pregnancy despite it being illegal under federal law in the United States. Many pregnant women perceive cannabis as relatively safe, especially since it can alleviate common pregnancy symptoms such as nausea, insomnia, and pain. This is a concern for healthcare providers who advise caution due to the growing evidence of potential harm.

Animal studies support these human findings, showing that exposure to THC — the primary psychoactive component of cannabis — can impair placental function, reducing blood flow and oxygen supply, which may hinder fetal development. In humans, imaging studies have demonstrated decreased placental blood flow and reduced amniotic fluid volume in cases of prenatal cannabis use.

Dr. Jamie Lo, an obstetrician specializing in high-risk pregnancies, emphasizes the importance of understanding that cannabis use during pregnancy can negatively impact placental health and fetal growth. Even in states like Oregon, where cannabis is legalized for recreational and medicinal purposes, medical experts recommend harm-reduction strategies. This involves reducing consumption when abstinence is not feasible, as even smaller amounts of cannabis can mitigate some risks.

While the current evidence underscores potential dangers, the authors acknowledge that further research is necessary to establish definitive causal relationships. Nevertheless, healthcare professionals advise pregnant women to avoid cannabis to promote healthier pregnancy outcomes. Public awareness and counseling are vital to reduce prenatal exposure and protect neonatal health.

Source: https://medicalxpress.com/news/2025-05-evidence-cannabis-pregnancy.html