Is heavy marijuana use a contributing factor to recurrent miscarriages in a female of childbearing age with a history of pregnancy loss?

Heavy Marijuana Use and Miscarriage Risk

Based on the most recent and highest-quality evidence, heavy marijuana use is associated with increased risk of adverse pregnancy outcomes including placental dysfunction, but the direct causal link to recurrent miscarriage specifically remains uncertain due to limited high-quality data on this specific outcome. 1

Direct Evidence on Pregnancy Loss

The available evidence does not establish a clear, direct causal relationship between cannabis use and miscarriage specifically:

• Perinatal mortality (which includes stillbirth but not early miscarriage) shows increased risk with prenatal cannabis use (adjusted odds ratio 1.5; 95% CI, 1.39-1.62), though this evidence is of very low to low certainty 2
• The most robust recent study (2023) examining cannabis exposure via biological sampling found associations with placental dysfunction-related outcomes but did not specifically report on first-trimester miscarriage rates 1
• Tobacco smoking during pregnancy is definitively associated with increased miscarriage risk, but cannabis has not been studied with the same rigor for this specific outcome 3, 4

Established Adverse Outcomes from Cannabis Use in Pregnancy

The American College of Obstetricians and Gynecologists recommends that people who are pregnant, trying to become pregnant, or breastfeeding abstain from using cannabis 3, based on the following established risks:

Placental Dysfunction and Related Complications

• Cannabis exposure beyond the first trimester is associated with a composite outcome of placental dysfunction (adjusted relative risk 1.32; 95% CI, 1.09-1.60), including small-for-gestational-age birth, medically indicated preterm birth, stillbirth, and hypertensive disorders 1
• Prenatal cannabis use is associated with gestational hypertension (adjusted relative risk 1.17; 95% CI, 1.13-1.21), preeclampsia (adjusted relative risk 1.08; 95% CI, 1.01-1.15), and placental abruption (adjusted relative risk 1.19; 95% CI, 1.05-1.36) 5

Fetal Growth and Birth Outcomes

• Cannabis use during pregnancy is associated with low birthweight 3, 4
• Small-for-gestational-age births occur more frequently with cannabis exposure 1, 2
• Preterm birth risk is increased (adjusted odds ratio 1.42; 95% CI, 1.19-1.69) 2

Neurodevelopmental Effects

• Fetal exposure to marijuana may have subtle effects on long-term neurobehavioral outcomes 3
• Studies suggest neurodevelopmental differences in offspring, including impairments in cognitive function and behavioral difficulties 6

Clinical Approach to This Patient

Immediate Counseling

• Strongly advise complete cessation of cannabis use based on ACOG recommendations and established risks to pregnancy outcomes 3
• Explain that while direct evidence linking cannabis to recurrent miscarriage is limited, cannabis causes placental dysfunction and other pregnancy complications that could theoretically contribute to pregnancy loss 1
• Emphasize that cannabis potency has dramatically increased (THC concentrations nearly doubled from 9% in 2008 to 17% in 2017), intensifying all health risks 7

Comprehensive Evaluation for Recurrent Pregnancy Loss

While addressing cannabis use, conduct standard workup for recurrent miscarriage:

• Evaluate for other established causes of recurrent pregnancy loss (genetic, anatomic, endocrine, immunologic factors)
• Screen for tobacco use, which has definitively established links to miscarriage 3, 4
• Assess for other substance use that may compound risks 3

Important Caveats

• The evidence quality is limited: Most cannabis studies are retrospective, subject to confounding and bias, and do not capture contemporary trends in high-potency products 4
• Timing matters: Cannabis exposure only during the first trimester showed weaker associations with adverse outcomes compared to ongoing use 1
• Dose-response relationships are poorly characterized: Studies typically do not adequately capture quantity, frequency, or potency of cannabis use 2

Bottom Line for Clinical Practice

Recommend complete cannabis cessation for any woman trying to conceive or who is pregnant 3. While you cannot definitively state that her cannabis use is causing her miscarriages based on current evidence, you can confidently state that:

1. Cannabis use increases risks of placental dysfunction, which could theoretically contribute to pregnancy loss 1
2. Cannabis use definitively increases other serious pregnancy complications 5, 1, 2
3. Major medical organizations recommend complete abstinence during pregnancy and preconception 3
4. A comprehensive evaluation for other causes of recurrent pregnancy loss should proceed concurrently