343 - Maternal and Neonatal Outcomes of Cannabis Use in Pregnancy; A Systematic Review and Meta-Analysis

Publication Number: 343.5705

Katelyn Sainz, Children's Hospital at Dartmouth-Hitchcock, Lebanon, NH, United States; Greg Marchand, The Marchand Institute for Minimally Invasive Surgery, Mesa, AZ, United States; Ahmed Masoud, The Marchand Institute for Minimally Invasive Surgery, Mesa, AZ, United States

Background: Following expansive legalization of cannabis in many parts of the United States, cannabis usage in pregnancy has increased several fold and is now the most commonly used illegal substance during pregnancy. There is a pressing need to understand the maternal and neonatal outcomes associated with this exposure. The fetal effects of cannabis are theorized to occur due to delta-9-tetrahydrocannabinol (THC), which crosses the placenta and binds to receptors present on fetal cells. This can result in alterations of levels of dopamine, GABA, serotonin, adrenalin, and glutamate; potentially interfering with placental and/or fetal development.
Despite recommendations, the harmful effects of cannabis during pregnancy are still controversial, and recent meta-analyses are not in complete agreement.

Objective: To quantify the maternal and neonatal outcomes of mothers using cannabis during pregnancy.

Design/Methods: We searched 6 databases for all relevant observational studies, from each database’s inception until 3/1/24.
Two reviewers separately screened the studies. Our initial search yielded 5184 studies, of which 51 (0.98%) were included.
Our study adhered to PRISMA guidelines and independent extraction by two researchers was utilized. We used a 95% confidence interval and the random effects model, as there was significant heterogeneity between studies.

Results: Cannabis consumption was associated with increased risks of low birth weight (RR=1.69,95% CI=(1.34,2.14),P < 0.0001), small for gestational age (RR=1.79,95% CI=(1.52, 2.1),P < 0.00001), major anomalies (RR=1.81,95% CI=(1.48, 2.23),P < 0.00001), decreased head circumference (MD=-0.34,95% CI=(-0.57,-0.11),P=0.004), birth weight (MD=-177.81,95% CI=(-224.72,-130.91),P < 0.00001), birth length (MD=-0.87,95% CI=(-1.15,-0.59),P < 0.00001), gestational age (MD=-0.21,95% CI=(-0.35,-0.08),P=0.002), NICU admission (RR=1.55,95% CI=(1.36,1.78),P < 0.00001), perinatal mortality (RR=1.72,95% CI=(1.09,2.71),P=0.02), and preterm delivery (RR=1.39,95% CI=(1.23,1.56),P < 0.00001). Cannabis usage was also associated with a decreased risk of gestational diabetes in pregnancy (RR=0.64,95% CI=(0.55,0.75),P < 0.00001).

Conclusion(s): Our systematic review included 7,920,383 women and found that cannabis use was associated with increased risks of low birth weight, small for gestational age, major anomalies, decreased head circumference, decreased neonatal weight, decreased birth length, decreased gestational age, NICU admission, perinatal mortality, and preterm delivery. We believe that the size of this study can help bring consensus to the discussion of cannabis use during pregnancy.

Figure 1
Figure 1.pdfPrisma diagram of our study search and selection process.

Figure 2
Maternal Outcomes.pdfMeta-analysis of all maternal outcomes.

Figure 3
Neonatal Weight Outcomes.pdfMeta-analysis of neonatal outcomes related to birth weight.