Am J Perinatol 2021; 38(S 01): e146-e154
DOI: 10.1055/s-0040-1708802
Original Article

Marijuana Use during Pregnancy and Preterm Birth: A Prospective Cohort Study

Mark A. Klebanoff
1   Center for Perinatal Research, The Abigail Wexner Research Institute at Nationwide Children's Hospital, Columbus, Ohio
2   Department of Pediatrics, The Ohio State University College of Medicine, Columbus, Ohio
Diana G. Wilkins
3   Center for Human Toxicology, Department of Pharmacology and Toxicology, The University of Utah, Salt Lake City, Utah
Sarah A. Keim
2   Department of Pediatrics, The Ohio State University College of Medicine, Columbus, Ohio
4   Center for Biobehavioral Health, The Abigail Wexner Research Institute, Nationwide Children’s Hospital, Columbus, Ohio
› Author Affiliations
Funding This study received funding from March of Dimes Foundation 6-FY16-160, U.S. Department of Health and Human Services, National Institutes of Health, National Institute on Drug Abuse R01DA042948, and National Center for Advancing Translational Sciences (UL1TR001070). The funding sources had no input in the study design; the data collection, interpretation or analysis; the writing of this report; or the decision to submit the article for publication.


Objective The aim of this study is to estimate the association between marijuana use during pregnancy and total, spontaneous and indicated preterm birth.

Study Design Prospective cohort study of women receiving antenatal care at The Ohio State University from 2010 to 2015. Marijuana use was assessed by questionnaire, record abstraction, and urine toxicology. Women were followed through the end of pregnancy. Relative risks were assessed with Poisson regression and time to delivery with proportional hazard models.

Results Of 363 eligible women, 119 (33%) used marijuana in pregnancy by at least one measure. In this high-risk cohort, preterm birth occurred to 36.0% of users and 34.6% of nonusers (p = 0.81). The unadjusted relative risk of all preterm birth was 1.06 (95% confidence interval [CI]: 0.76–1.47); the adjusted relative risk was similar 1.04 (95% CI: 0.72–1.50). Spontaneous preterm birth was nonsignificantly elevated among users before 1.32 (95% CI: 0.89–1.96), and after 1.21 (95% CI: 0.76–1.94) adjustment. Indicated preterm birth was nonsignificantly reduced before 0.52 (95% CI: 0.22–1.23) and after 0.75 (95% CI: 0.29–2.15) adjustment. The unadjusted hazard ratio (HR) for time to preterm birth was 1.26 (95% CI: 0.84–2.00); the adjusted HR was 1.32 (95% CI: 0.80–2.07). Both unadjusted 1.77 (95% CI: 1.06–2.93) and adjusted 2.16 (95% CI: 1.16–4.02) HRs for spontaneous preterm birth were significantly elevated, primarily due to an increased risk of spontaneous birth <28 weeks among users. The unadjusted and adjusted HRs for time to indicated preterm birth were 0.69 (95% CI: 0.33–1.43) and 0.58 (95% CI: 0.23–1.46).

Conclusion Marijuana use was not associated with total preterm birth in this cohort, suggesting that among women already at high risk of preterm birth, marijuana does not increase risk further. However, there was a suggestion that pregnant women who use marijuana may deliver earlier, particularly from spontaneous preterm birth, than women who do not use marijuana.

Key Points

  • Marijuana was not associated with risk of all preterm birth.

  • Marijuana was not associated with reduced time to delivery.

  • However, users had reduced time to spontaneous preterm birth.


This study presented at the 30th Annual Meeting of the Society for Pediatric and Perinatal Epidemiologic Research, June 19 to 20, 2017 and the 50th Annual Meeting of the Society for Epidemiologic Research, June 20 to 23, 2017, both in Seattle, Washington.

Supplementary Material

Publication History

Received: 18 December 2019

Accepted: 13 February 2020

Article published online:
01 April 2020

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