Among 40,806 pregnancies with preconception cannabis use, daily users were 2.7 times more likely to continue using during pregnancy, suggesting preconception screening could enable early intervention.
OB-GYNs, primary care providers, women planning pregnancy who use cannabis, and public health professionals focused on prenatal health.
What the researchers found
Daily preconception cannabis use was associated with 2.66 times greater risk of prenatal use compared to monthly or less use. Nearly half (45.1%) of all preconception cannabis users screened positive during pregnancy.
Why it matters
If frequency of preconception use predicts prenatal use this strongly, healthcare providers can identify high-risk individuals before pregnancy and provide targeted education and support.
The numbers in context
40,806 pregnancies. 45.1% screened positive for prenatal use. Daily preconception use: aPR = 2.66 (95% CI: 2.59-2.73). Weekly: aPR = 1.99 (95% CI: 1.93-2.05). 65.7% non-White, 27.6% aged <25.
How the study worked
Retrospective observational study of 40,806 pregnancies (36,622 unique individuals) in Kaiser Permanente Northern California (2011-2022) with self-reported preconception cannabis use, using modified Poisson models.
What this study cannot tell us
Single healthcare system in California. Self-report may underestimate use. Cannot account for all confounders. Excluded 2020 (pandemic year).
How to read the evidence
Very large cohort with universal screening data and robust statistical methods — strong evidence for the dose-response relationship.
When this study was published
Recent study spanning over a decade of screening data (2011-2022) from a healthcare system with universal prenatal cannabis screening.
The bigger picture
Cannabis use during pregnancy is a growing concern. Identifying that preconception use frequency is the strongest predictor enables a shift from pregnancy-stage intervention to preconception prevention.
Questions still open
- Could preconception cannabis reduction programs prevent prenatal exposure? Should reproductive health screenings routinely include cannabis use frequency assessment?
Common questions
Does using cannabis before pregnancy mean you'll use it during?
What percentage of preconception users continue during pregnancy?
Read the original research
Association of preconception cannabis use frequency with cannabis use during early pregnancy.
BMC pregnancy and childbirth, 25(1), 1044
Citation
Young-Wolff, Kelly C; Chi, Felicia W; Campbell, Cynthia I; Does, Monique B; Wysota, Christina N; Ansley, Deborah; Castellanos, Carley; Lapham, Gwen T. (2025). Association of preconception cannabis use frequency with cannabis use during early pregnancy.. BMC pregnancy and childbirth, 25(1), 1044. https://doi.org/10.1186/s12884-025-08190-y
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