Table 1. Unadjusted Prevalence of Prenatal Cannabis Use During Early Pregnancy in Kaiser Permanente Northern California, by Number of Co-occurring Substances, 2009-2018 (N = 367 138)a.
| Substance use | Unadjusted prevalence of cannabis and co-occurring substance use during pregnancy, % | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| 2009 | 2010 | 2011 | 2012 | 2013 | 2014 | 2015 | 2016 | 2017 | 2018 | |
| Any cannabis use | 4.52 | 4.93 | 5.36 | 5.33 | 5.41 | 5.98 | 6.23 | 6.54 | 7.25 | 8.01 |
| No. of co-occurring substances | ||||||||||
| Cannabis only | 2.62 | 3.12 | 3.42 | 3.46 | 3.64 | 4.24 | 4.55 | 4.91 | 5.47 | 5.77 |
| Cannabis and 1 other substance | 1.29 | 1.24 | 1.34 | 1.32 | 1.31 | 1.30 | 1.27 | 1.23 | 1.38 | 1.78 |
| Cannabis and ≥2 other substances | 0.61 | 0.57 | 0.59 | 0.55 | 0.46 | 0.44 | 0.41 | 0.39 | 0.40 | 0.46 |
| Type of co-occurring substance use | ||||||||||
| Cannabis only | 2.62 | 3.12 | 3.42 | 3.46 | 3.64 | 4.24 | 4.55 | 4.91 | 5.47 | 5.77 |
| Cannabis and alcohol | 1.19 | 1.15 | 1.19 | 1.19 | 1.14 | 1.12 | 1.07 | 1.04 | 1.28 | 1.75 |
| Cannabis and nicotine | 1.16 | 1.07 | 1.12 | 1.04 | 0.91 | 0.88 | 0.81 | 0.80 | 0.71 | 0.74 |
| Cannabis and pharmaceutical opioids | 0.08 | 0.06 | 0.07 | 0.08 | 0.09 | 0.09 | 0.10 | 0.07 | 0.07 | 0.06 |
| Cannabis and stimulants | 0.18 | 0.16 | 0.21 | 0.17 | 0.15 | 0.18 | 0.18 | 0.17 | 0.18 | 0.20 |
a
When presenting the crude prevalence for type of co-occurring substance use, with the exception of cannabis only, categories are not mutually exclusive, and patients can be included in more than 1 group (eg, cannabis and alcohol, cannabis and nicotine). Therefore, the categories within a year do not add up to the total prevalence of cannabis use in that year.