“Background and aims: Cannabis use is increasingly common among pregnant individuals and might be a risk factor for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. We aimed to test whether prenatal cannabis use is associated with increased risk of SARS-CoV-2 infection during pregnancy.
Design: Retrospective cohort study.
Setting: California USA.
Participants: 58,114 pregnancies (with outcomes from 3/5/2020 to 9/30/2021) among 57,287 unique pregnant women aged 14-54 years who were screened for prenatal substance use, enrolled in Kaiser Permanente Northern California (KPNC) (a healthcare system), and had not tested positive for COVID-19 prior to pregnancy onset.
Measurements: We utilized data from the KPNC electronic health record. Cannabis use status (current, recently quit, non-user) was based on universal screenings during prenatal care (including ≥1 urine toxicology test and self-reported use on a self-administered questionnaire). SARS-CoV-2 infection (based on polymerase chain reaction (PCR) tests) was estimated in time-to-event analyses using Cox proportional hazard regression models adjusting for covariates. Secondary analyses examined differences in a) SARS-CoV-2 positivity testing rates and b) SARS-CoV-2 infection rates among those tested.
Findings: We observed 348,810 person-months of follow-up time in our cohort with 41,064 SARS-CoV-2 PCR tests, and 6% (n=2,414) of tests being positive. At the start of follow-up, 7% of pregnant individuals had current use, 12% had recently quit, and 81% did not use cannabis. Adjusting for covariates, current use was associated with lower rates of SARS-CoV-2 infection (adjusted hazard ratio [aHR]=0.60,95% confidence interval [CI]:0.49-0.74) than non-use. Those who had recently quit did not differ from non-cannabis users in infection rates (aHR=0.96,95%CI:0.86-1.08). Sensitivity analyses among patients who received a SARS-CoV-2 test also found lower odds of infection associated with current versus no cannabis use (aOR=0.76,CI:0.61-0.93).
Conclusions: Current cannabis use appears to be associated with a reduced risk of severe acute respiratory syndrome coronavirus 2 infection among pregnant individuals.”