Cannabis use in Pregnancy
Cannabis use in pregnancy and neonatal outcomes: a systematic review and meta-analysis
- In the US, cannabis is the most common illicit drug used among women of childbearing age and during pregnancy.
- Frequency of cannabis use during pregnancy has more than doubled in the US the past decade with past-month cannabis use increasing from 3.4% In 2002 to 7% In 2017.
- At present, the US Surgeon General and American College of Obstetricians and Gynecologists advise pregnant and lactating women to abstain from using cannabis.
- A 2016 systematic review assessing the adverse neonatal outcomes from maternal cannabis use identified few studies. We updated this review to capture the most current evidence.
Living systematic review
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 10th percentile given sex and gestational age; SGA) and perinatal mortality.
Risk of Bias: 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 48 eligible studies. Of these, 47 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 uncertain (n = 29 studies; very low CoE)
- Following statistical adjustment, we observed increased odds of PTB (n = 36 studies; low CoE) and SGA (n = 17 studies; low CoE) in women who used cannabis in pregnancy
- Unadjusted estimates suggest that the odds of perinatal mortality were increased with cannabis use in pregnancy (n = 15 studies; very low CoE)
- We found insufficient data on the relationship between cannabis use in pregnancy and perinatal mortality that accounted for confounders (e.g., maternal age, prenatal smoking)
Summary of Findings (GRADE)
|Certainty of the Evidence||Relationship||Rationale for CoE Rating|
N = 176, 055
|⨁◯◯◯Very low||Unclear relationship between cannabis use in pregnancy and birthweight||Downgraded 1 level for inconsistency|
Preterm Birth (<37 weeks)
N = 14,144,430
|⨁⨁◯◯Low||After adjustment, increased odds of PTB with cannabis use during pregnancy||Downgraded 1 level for inconsistency ; upgraded 1 level for accounting for all plausible confounders|
Perinatal death (e.g., stillbirth, fetal demise)
N = 13,518,099
|⨁◯◯◯Very low||Increased odds of perinatal mortality with cannabis use during pregnancy (unadjusted association)||Downgraded 1 level for inconsistency|
SGA (<10th percentile)
N = 836,118
|⨁⨁◯◯Low||After adjustment, increased odds of SGA birth with cannabis use during pregnancy||Downgraded 1 level for inconsistency; upgraded 1 level for accounting for all plausible confoundersAbbreviations. SGA: small-for-gestational age|
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 birthweight, PTB, perinatal mortality, and SGA.
- Despite our findings indicating potential perinatal harm 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.
Gaps in Evidence
- 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.
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Full Systematic Review:
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