What Research Shows About Marijuana Use During Pregnancy and Breastfeeding
Marijuana crosses the placenta and appears in breast milk, with emerging evidence linking prenatal exposure to fetal growth restriction, possible stillbirth and preterm birth, and neurological development problems in children.
Quick Facts
What This Study Found
This review examined the evidence on marijuana use during pregnancy and lactation, noting that 3-30% of pregnant women use marijuana depending on the population studied.
THC freely crosses the placenta and is found in breast milk. The review identified several potential adverse outcomes: fetal growth restriction, possible associations with stillbirth and preterm birth, and emerging evidence of neurological effects including hyperactivity, poor cognitive function, and changes in dopamine receptors in exposed children.
However, the evidence was far from uniform. Most studies were confounded by concurrent tobacco and other drug use, sociodemographic factors, lack of trimester-specific exposure data, and reliance on self-report without biological verification.
Key Numbers
Prevalence of use: 3-30% across populations; THC crosses placenta and enters breast milk; associated outcomes: fetal growth restriction, possible stillbirth, preterm birth, hyperactivity, cognitive effects
How They Did This
Narrative review of published literature on marijuana use in pregnancy and lactation, with emphasis on perinatal outcomes and fetal neurodevelopment. Published in a leading obstetrics journal.
Why This Research Matters
As marijuana legalization expands, more women may use it during pregnancy, potentially unaware of risks. This review highlighted both the potential harms and the significant gaps in evidence that make definitive risk counseling difficult.
The Bigger Picture
Contemporary marijuana is substantially more potent than the products studied in the 1980s when much of the foundational research was done. This means older studies may underestimate risks, and new research with current products is urgently needed.
What This Study Doesn't Tell Us
Most existing studies have significant confounding from tobacco and other substance co-use. Self-reported marijuana use is unreliable. Lack of dose quantification by trimester. Difficulty isolating marijuana effects from sociodemographic risk factors.
Questions This Raises
- ?What are the effects of today's higher-potency marijuana on fetal development?
- ?Are there critical windows of vulnerability during pregnancy?
- ?How long does THC persist in breast milk after use?
- ?Do CBD-only products carry the same risks?
Trust & Context
- Key Stat:
- 3-30% of pregnant women use marijuana depending on population
- Evidence Grade:
- Comprehensive review in a major obstetrics journal, but hampered by the limitations of the underlying studies, which are heavily confounded.
- Study Age:
- Published in 2015. Cannabis potency has continued to increase, and more research on prenatal exposure has been published.
- Original Title:
- Marijuana use in pregnancy and lactation: a review of the evidence.
- Published In:
- American journal of obstetrics and gynecology, 213(6), 761-78 (2015)
- Authors:
- Metz, Torri D(8), Stickrath, Elaine H(2)
- Database ID:
- RTHC-01017
Evidence Hierarchy
Summarizes existing research on a topic.
What do these levels mean? →Frequently Asked Questions
Is marijuana safe during pregnancy?
The evidence reviewed suggests potential risks including fetal growth restriction and developmental effects on the child's brain. While data quality is limited, no study has demonstrated safety, and the review recommended against use during pregnancy and lactation.
Does THC get into breast milk?
Yes. THC is fat-soluble and is found in breast milk. Because the infant brain is still developing, exposure through breastfeeding is a concern, though the long-term effects of this exposure are not well studied.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-01017APA
Metz, Torri D; Stickrath, Elaine H. (2015). Marijuana use in pregnancy and lactation: a review of the evidence.. American journal of obstetrics and gynecology, 213(6), 761-78. https://doi.org/10.1016/j.ajog.2015.05.025
MLA
Metz, Torri D, et al. "Marijuana use in pregnancy and lactation: a review of the evidence.." American journal of obstetrics and gynecology, 2015. https://doi.org/10.1016/j.ajog.2015.05.025
RethinkTHC
RethinkTHC Research Database. "Marijuana use in pregnancy and lactation: a review of the ev..." RTHC-01017. Retrieved from https://rethinkthc.com/research/metz-2015-marijuana-use-in-pregnancy
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.