Cannabis Pregnancy Risks: Evidence and Guidance

Cannabis Use During Pregnancy: What the Evidence Shows

Cannabis use during pregnancy is linked to low birth weight and preterm birth. The American College of Obstetricians and Gynecologists advises people to stop cannabis use before conception and to keep avoiding it during pregnancy. The US Surgeon General issued the same advice in 2019. No cannabis product is FDA approved for use in pregnancy.

cannabis use during pregnancy

How many pregnant people use cannabis

Federal survey data put prenatal cannabis use at about 5% of pregnant women in the US. Rates are higher among people aged 18 to 24. Self-report surveys undercount use because of stigma and because cannabis remains illegal in some states.

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Outcomes tied to prenatal exposure

• Lower birth weight. Low birth weight means under 5 pounds 8 ounces, or 2,500 grams.
• Preterm birth, defined as delivery before 37 weeks of gestation.
• Higher rates of newborn intensive care unit admission.
• Childhood outcomes. Cohorts that followed children to ages 9 to 11 reported more attention problems and lower scores on some thinking tests.

These are associations. They do not prove that cannabis caused the outcomes.

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How THC reaches the fetus

THC crosses the placenta. Fetal brain tissue carries cannabinoid receptors. Animal studies show changes in brain development after exposure. Human data come from observation of pregnancies, not from controlled experiments.

Breastfeeding

THC passes into breast milk. The Surgeon General advises against cannabis use while breastfeeding. ACOG and the American Academy of Pediatrics recommend abstaining. Reports from small studies list sedation and slower weight gain in infants. The data set is thin.

Limits of the research

No randomized trial exists, and none will be run. Assigning pregnant people to use cannabis would be unethical. All human evidence comes from observational cohorts. People who use cannabis also use tobacco and alcohol at higher rates, which confounds results. Dose, potency, and timing data are incomplete. Some studies find no link to birth defects. Others find mixed results.

What clinicians advise

• Stop cannabis before trying to conceive.
• Do not treat morning nausea with cannabis. ACOG points to approved anti-nausea drugs instead.
• Tell your obstetric provider about cannabis use. Screening is routine at the first prenatal visit.
• Avoid CBD products. The FDA warns against CBD in pregnancy and while breastfeeding.

Help to stop

Behavioral therapy is the main treatment for cannabis use disorder. The SAMHSA National Helpline is 1-800-662-4357 and runs 24 hours a day.