Systematically Testing the Evidence on Marijuana

Living systematic review

Search:

• CINAHL (EBSCOHost)
• EBM Reviews Cochrane Database of Systematic Reviews (Ovid)
• Global Health (Ovid)
• MEDLINE (Ovid)
• PsycInfo (Ovid)

Screening: Cohort or case-control studies assessing the effects of prenatal cannabis use on risk of preterm birth (less than 37 weeks of gestation; PTB), low birth weight (less than 2,500 grams; LBW), small-for-gestational-age (weight less than the 10^th percentile given sex and gestational age; SGA) and perinatal mortality.

Risk of Bias (RoB): Newcastle-Ottawa tool for cohort studies and case-control studies

GRADE: Overall certainty of evidence (CoE) for each outcome using the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) approach

Meta-Analysis: Pairwise meta-analyses using adjusted and unadjusted data.

Updates: Search to be updated every 6 months with new reports as needed

• We identified 53 eligible studies. Of these, 52 were cohort studies and 1 was a case-control study. In general, we rated these studies as low to moderate risk of bias:
  • The relationship between cannabis use in pregnancy and birthweight is unclear (n = 31 studies; low CoE)
  • Following statistical adjustment, we observed increased odds of PTB (n = 41 studies; low CoE) and SGA (n = 21 studies; low CoE) in infants of individuals who used cannabis in pregnancy
  • After adjustment, the odds of perinatal mortality were increased with cannabis use in pregnancy, but the CoE was very low (n = 17 studies)

Summary of Findings (GRADE)

Abbreviations. RoB: risk of bias; SGA: small-for-gestational age; PTB: preterm birth
GRADE certainty of evidence: Very low ⨁◯◯◯; Low ⨁⨁◯◯; Moderate ⨁⨁⨁◯; High ⨁⨁⨁⨁

• Overall, we found very low to low CoE of the associations of cannabis use in pregnancy and preterm birth, perinatal mortality, and small-for-gestational-age.
• Despite our findings indicating potential perinatal harms of cannabis use during pregnancy, our certainty in them is low. As prenatal cannabis use becomes more commonplace, this review can help guide healthcare providers with counseling, management, and addressing the limited existing safety data.

• High quality studies that consider formulation and dosing of cannabis, as well as the timing and duration of use, are needed to help elucidate the associations between prenatal cannabis exposure and perinatal outcomes.
• High quality studies that fully report both unadjusted and adjusted data are also needed.

Brown QL, Sarvet AL, Shmulewitz D, Martins SS, Wall MM, Hasin DS. Trends in Marijuana Use Among Pregnant and Nonpregnant Reproductive-Aged Women, 2002-2014. JAMA. 2017;317(2):207-209. doi:10.1001/jama.2016.17383

Conner SN, Bedell V, Lipsey K, Macones GA, Cahill AG, Tuuli MG. Maternal marijuana use and adverse neonatal outcomes: a systematic review and meta-analysis. Obstet Gynecol. 2016;128(4):713-723.

Guyatt GH, Oxman AD, Vist GE, et al. GRADE: an emerging consensus on rating quality of evidence and strength of recommendations. BMJ. 2008;336(7650):924-926.

Marchand G, Masoud AT, Govindan M, et al. Birth Outcomes of Neonates Exposed to Marijuana in Utero: A Systematic Review and Meta-analysis. JAMA Netw Open. 2022;5(1):e2145653. Published 2022 Jan 4. doi:10.1001/jamanetworkopen.2021.45653

Marijuana use during pregnancy and lactation. Committee Opinion No. 637. American College of Obstetricians and Gynecologists. Obstet Gynecol 2015;126(1):234–238.

Martin CE, Longinaker N, Mark K, Chisolm MS, Terplan M. Recent trends in treatment admission for marijuana use during pregnancy. J Addict Med. 2015;9(2):99-104. doi: 10.1097/ADM.0000000000000095

U.S. Surgeon General’s Advisory: Marijuana use and the developing brain. https://www.hhs.gov/surgeongeneral/reports-and-publications/addiction-and-substance-misuse/advisory-on-marijuana-use-and-developing-brain/index.html Last accessed August 24, 2021.

Volkow ND, Han B, Compton WM, McCance-Katz EF. Self-reported Medical and Nonmedical Cannabis Use Among Pregnant Women in the United States. JAMA. 2019;322(2):167-169. doi:10.1001/jama.2019.7982

Wells G, Shea B, O’Connell D, Peterson J, Welch V, Losos M, Tugwell P. The Newcastle-Ottawa Scale (NOS) for assessing the quality of nonrandomised studies in meta-analyses. 2013, http://www.ohri.ca/programs/clinical_epidemiology/oxford.asp. Last accessed August 25, 2021.