Cannabis and pregnancy

In a multicenter observational cohort study (1):

• a composite adverse pregnancy outcome (small-for-gestational-age birth, medically indicated preterm birth, stillbirth, or hypertensive disorders of pregnancy) was more frequent in pregnant individuals with cannabis exposure ascertained by a urine drug assay (25.9%; n = 610) compared with unexposed individuals (17.4%; n = 8647)
• risk for an adverse outcome was higher among those who continued to use cannabis beyond the first trimester
• study authors concluded:
  • cannabis use should be avoided during pregnancy to optimize maternal and neonatal outcomes

Another study found (2):

• prenatal cannabis linked to increased risk of gestational hypertension, preeclampsia, weight gain and placental abruption

A review notes (3):

• in utero exposure to marijuana has been linked to a “withdrawal”-like syndrome in newborns, demonstrated by an increase in startles and tremors and reduced habituation to light
• tetrahydrocannabinol is a fat-soluble molecule excreted in human breast milk in moderate amounts
  • in chronic heavy users, the milk-to-plasma ratio can be as high as 8:1 and metabolites of cannabis are found in infant feces and urine, suggesting that it might be absorbed and metabolized by the infant

A further review notes that potential harms of cannabis or cannabinoid use in pregnancy are likely outweigh the benefits (4).

Reference:

1. Metz TD, Allshouse AA, McMillin GA, et al. Cannabis Exposure and Adverse Pregnancy Outcomes Related to Placental Function. JAMA. 2023;330(22):2191–2199. doi:10.1001/jama.2023.21146
2. Young-Wolff KC, Adams SR, Alexeeff SE, et al. Prenatal Cannabis Use and Maternal Pregnancy Outcomes. JAMA Intern Med. Published online July 22, 2024.
3. Badowski S, Smith G. Cannabis use during pregnancy and postpartum. Can Fam Physician. 2020 Feb;66(2):98-103.
4. Hsu M, Shah A, Jordan A, Gold MS, Hill KP. Therapeutic Use of Cannabis and Cannabinoids: A Review. JAMA. Published online November 26, 2025.