Marijuana Use During Pregnancy Linked to Serious Health Risks, New Research Warns
Using marijuana during pregnancy is associated with serious health complications for both the mother and baby, according to a comprehensive new meta-analysis. The study highlights increased risks of poor fetal development, low birth weight, premature birth, and even infant death.
Alarming Findings from a New Meta-Analysis
Led by Dr. Jamie Lo, an obstetrician at Oregon Health & Science University, the study analyzed 51 studies involving more than 21 million participants. Published in JAMA Pediatrics, it found that marijuana use during pregnancy is linked to:
- 52% higher risk of preterm birth (before 37 weeks)
- 75% higher risk of low birth weight (under 5.5 pounds)
- 29% higher risk of perinatal mortality (death shortly before or after birth)
“The most striking finding is the increased risk of perinatal mortality,” said Dr. Lo. “That’s one of the most devastating outcomes imaginable.”
How Cannabis Affects Fetal Health
Cannabis can negatively impact placental blood flow and fetal lung development. These impairments reduce oxygen and nutrients delivered to the fetus—both critical for healthy growth.
Despite growing evidence of harm, many people continue to view marijuana as harmless because it is “natural.” Dr. Lo cautioned against this belief:
“People think marijuana is safe because it’s natural—but so are opium and tobacco, which clearly carry major risks during pregnancy.”
A Growing Public Health Concern
Marijuana use among pregnant women is on the rise. A 2019 national survey found that cannabis use more than doubled between 2002 and 2017 among American women aged 12 to 44. Most usage occurs in the first trimester, often for recreational purposes.
Comparing Cannabis with Other Risky Substances
Other substances known to harm pregnancies include:
- Alcohol – causes fetal alcohol syndrome, leading to intellectual and physical disabilities
- Tobacco – linked to lung and brain damage in fetuses
- Opioids – increase risks of birth defects, stillbirth, and addiction in newborns
Due to ethical limitations, clinical trials exposing pregnant women to harmful substances are prohibited. As a result, studies rely on self-reported data from mothers, which can make findings difficult to interpret with certainty.
Improving Quality of Evidence
Previously, marijuana research during pregnancy was rated as low-certainty. However, the new study uses the GRADE framework and finds evidence now ranges from low to moderate certainty, a significant improvement over past assessments. Experts like Brianna Moore from the Colorado School of Public Health agree that the evidence base is strengthening.
Confusion Around Cannabis Safety
Legalization has fueled public misconceptions about marijuana’s safety—especially among expectant parents. Health providers also face challenges in counseling patients due to conflicting or outdated data.
“There’s no clear public health messaging,” said Dr. Lo. “We’re working to create updated reviews and tools to help clinicians better guide their patients.”
Earlier studies may not reflect today’s realities, as modern cannabis strains are far more potent than those used in the 1980s and 1990s.
Broader Health Risks of Marijuana
Recent research suggests marijuana poses health risks far beyond pregnancy. These include:
- 42% increased risk of stroke
- 25% increased risk of heart attack
- Heart complications, such as arrhythmias and myocarditis
- Mental health issues in young users, including anxiety, depression, and even suicide attempts
- Cognitive impairments and psychotic-like behaviors in children born to marijuana users
- Cannabinoid Hyperemesis Syndrome – a condition causing severe vomiting from daily use
Final Advice: Avoid THC During Pregnancy
Given the mounting evidence of harm, Dr. Lo delivered a clear message:
“Ideally, it’s best not to be exposed to THC at all during pregnancy.”
