Growing evidence links marijuana use during pregnancy to lower birth weight, preterm birth, and impaired child brain development
A review found that despite study limitations, accumulating data links prenatal marijuana exposure to decreased birth weight, spontaneous preterm birth, and impaired neurodevelopment, with THC also detected in breast milk.
Quick Facts
What This Study Found
Marijuana is the most commonly used illicit drug during pregnancy, and its use is increasing in the US. While much of the existing research has limitations (study design, confounding factors), a growing body of data suggests adverse outcomes from prenatal exposure.
Associations have been identified with decreased birth weight, increased spontaneous preterm birth, and impaired neurodevelopment among children and adults who were exposed in utero. Moderate concentrations of marijuana have also been detected in breast milk.
Multiple professional societies have issued clear statements against marijuana use during pregnancy and lactation.
Key Numbers
Marijuana: most commonly used illicit drug in pregnancy. Prevalence increasing in US. Associations: decreased birth weight, increased preterm birth, impaired neurodevelopment. THC detected in breast milk at moderate concentrations.
How They Did This
Narrative review of existing research on marijuana use during pregnancy, covering birth outcomes, neurodevelopmental effects, and breast milk transmission.
Why This Research Matters
As marijuana becomes more available and socially accepted, pregnant women may perceive less risk from use. This review highlights that despite imperfect evidence, the signal for harm is consistent enough that professional medical organizations recommend against use during pregnancy and breastfeeding.
The Bigger Picture
The challenge with prenatal cannabis research is that randomized trials would be unethical, so all evidence is observational and subject to confounding (women who use marijuana during pregnancy may also smoke tobacco, use alcohol, have poorer nutrition, etc.). Despite these limitations, the consistency of findings across studies has been sufficient for professional societies to advise against use.
What This Study Doesn't Tell Us
Existing research is limited by observational designs, confounding factors (tobacco, alcohol, socioeconomic status), and self-reported cannabis use. THC potency has increased substantially over time, so older studies may underestimate current risks. The review does not differentiate between occasional and heavy use.
Questions This Raises
- ?Does the route of cannabis administration (smoking vs edibles) affect prenatal risk?
- ?At what trimester is exposure most harmful?
- ?Would CBD without THC carry the same risks?
Trust & Context
- Key Stat:
- Professional societies recommend against marijuana use during pregnancy and breastfeeding
- Evidence Grade:
- Narrative review of observational studies. Consistent signal for harm but limited by study design and confounding in the underlying evidence.
- Study Age:
- Published in 2017. Research on prenatal cannabis exposure has continued with more attention to product potency and delivery methods.
- Original Title:
- Marijuana Use in Pregnancy: Concerns in an Evolving Era.
- Published In:
- Journal of midwifery & women's health, 62(3), 363-367 (2017)
- Authors:
- Foeller, Megan E, Lyell, Deirdre J
- Database ID:
- RTHC-01381
Evidence Hierarchy
Summarizes existing research on a topic.
What do these levels mean? →Frequently Asked Questions
Is marijuana safe during pregnancy?
Multiple professional medical societies recommend against marijuana use during pregnancy and breastfeeding. While the research has limitations, accumulating evidence associates prenatal exposure with lower birth weight, preterm birth, and neurodevelopmental effects in children.
Does marijuana get into breast milk?
Yes. Moderate concentrations of marijuana have been detected in breast milk. THC is fat-soluble and can accumulate in breast milk, potentially exposing nursing infants to psychoactive compounds.
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Cite This Study
https://rethinkthc.com/research/RTHC-01381APA
Foeller, Megan E; Lyell, Deirdre J. (2017). Marijuana Use in Pregnancy: Concerns in an Evolving Era.. Journal of midwifery & women's health, 62(3), 363-367. https://doi.org/10.1111/jmwh.12631
MLA
Foeller, Megan E, et al. "Marijuana Use in Pregnancy: Concerns in an Evolving Era.." Journal of midwifery & women's health, 2017. https://doi.org/10.1111/jmwh.12631
RethinkTHC
RethinkTHC Research Database. "Marijuana Use in Pregnancy: Concerns in an Evolving Era." RTHC-01381. Retrieved from https://rethinkthc.com/research/foeller-2017-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.