Am J Perinatol 2020; 37(01): 059-065
DOI: 10.1055/s-0039-1696719
SMFM 2019
Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

Impact of Marijuana Legalization on Prevalence of Maternal Marijuana Use and Perinatal Outcomes

Mayi Gnofam
1  Department of Obstetrics and Gynecology, University of Colorado Denver, Aurora, Colorado
2  Department of Obstetrics and Gynecology, Maison Blanche's Hospital, University of Reims, Champagne-Ardenne, France
Amanda A. Allshouse
3  Department of Obstetrics and Gynecology, University of Utah Health, Salt Lake City, Utah
Elaine H. Stickrath
4  Department of Obstetrics and Gynecology, Denver Health and Hospital Authority, Denver, Colorado
5  University of Colorado School of Medicine, Aurora, Colorado
Torri D. Metz
3  Department of Obstetrics and Gynecology, University of Utah Health, Salt Lake City, Utah
› Author Affiliations
Funding This project was completed using resources (REDcap) from the Colorado Clinical and Translational Sciences Institute (CCTSI) with the Development and Informatics Service Center (DISC) grant support (NIH/NCRR Colorado CTSI Grant Number UL1 RR025780). During the completion of this study, T.D.M. was supported by the National Institute on Child Health and Human Development under award number 5K12HD001271–18. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
Further Information

Publication History

19 July 2019

26 July 2019

Publication Date:
06 September 2019 (online)


Objective We aimed to assess whether marijuana legalization was associated with a difference in prevalence of prenatal use or an increase in incidence of adverse perinatal outcomes.

Study Design The present study is a retrospective cohort of September and October deliveries in the years 2012 through 2015 at a tertiary center in Colorado. Primary outcome of the study was use of marijuana, defined by self-report or biodetection. Secondary outcomes of the study included growth restriction, spontaneous preterm birth, stillbirth, preeclampsia, and neonatal or maternal death. Marijuana use prevalence was compared by year, and secondary outcomes between two periods, before and after the opening of the first recreational dispensary.

Results A total of 2,392 pregnant women were included (1,165 before legalization and 1,227 after). More women used marijuana over the period of legalization (trend p = 0.01). Odds of marijuana use were higher after legalization versus before (adjusted odds ratio [aOR] = 1.8, 95% confidence interval [CI]: 1.2–2.6). Incidence of growth restriction was higher after legalization (2.9 vs. 5.1%, p = 0.0084). This difference persisted after adjustment for ethnicity and other drugs in multivariable modeling (aOR = 1.9, 95%CI: 1.2–3.0).

Conclusion The prevalence of prenatal marijuana use increased over the time of legalization. Further investigation into the population impact of legalization on obstetrical outcomes is warranted given the observed increase in growth restriction.


This study was presented as a poster at the Society for Maternal-Fetal Medicine Annual Meeting, Las Vegas, NV, February 11 to 16, 2019.