Cannabis is the most commonly used illicit substance during pregnancy in the United States (U.S.) (Substance Abuse and Mental Health Services Administration [SAMHSA], 2020), with a pooled prevalence of 6.8% based on data from the 2021-2023 National Survey on Drug Use and Health (Grigsby et al., 2025). However, the true prevalence is likely higher due to underreporting. Previous studies indicated that pregnant women are nearly twice more likely to screen positive for cannabis via drug tests than through self-reported measures (Young-Wolff et al., 2017). Among low-income women giving birth in an urban medical center, 11.0% self-reported cannabis use in the past three months, while 28.0% tested positive (Beatty et al., 2012). In addition, pregnant women reported higher rates of cannabis use than their non-pregnant counterparts, and those who used it tend to do so more frequently. For instance, nearly half pregnant women who used cannabis in the past year did so daily for at least 100 days, compared to one-third of non-pregnant women. Additionally, 18.0% of pregnant cannabis users met the criteria for cannabis use disorder (CUD), compared to 11.0% of non-pregnant users (Ko et al., 2015).

Pregnant women may use cannabis recreationally for its psychoactive effects or medically for its antiemetic properties to relieve nausea and vomiting. Studies showed that pregnant women experiencing these symptoms were significantly more likely to use cannabis (Roberson et al., 2014, Young-Wolff et al., 2019), and 69.0% of Colorado dispensaries have recommended cannabis for treating nausea in pregnancy (Dickson et al., 2018). Perceptions of cannabis safety also influence use. For instance, roughly two-thirds of women believed occasional cannabis use poses no or only slight risk (Ko et al., 2015), and those who perceived it as harmless were less likely to discontinue use during pregnancy (Mark et al., 2017).

Cannabis use during pregnancy has been associated with adverse maternal and neonatal outcomes, including low birth weight, small-for-gestational-age births, placental abruption, neonatal intensive care unit admission, and/or lower APGAR scores (Corsi et al., 2019, Young-Wolff et al., 2024). Long-term effects on offspring include impaired brain development, behavioral problems, and academic difficulties (El Marroun et al., 2016, Goldschmidt et al., 2012). The American College of Obstetricians and Gynecologists (ACOG) recommends universal screening and counseling for cessation of cannabis use during pregnancy (ACOG, 2017). Despite this, the proportion of pregnant women among all substance use treatment admissions has remained stable at 4.0% over the past three decades, while cannabis-related admissions among pregnant women have risen from 29.0% in 1992 to 43.0% in 2012 (Martin et al., 2015).

Although previous studies have examined prevalence of cannabis use and access to care among pregnant women, research on their treatment outcomes remains limited. In general, individuals mandated to treatment by the justice system demonstrate higher attendance and retention rates than voluntarily admissions, though findings on treatment completion are mixed (National Institute on Drug Abuse [NIDA], 2014). Treatment setting also influences completion rates, with residential programs reporting higher completion rates than those of outpatient programs (SAMHSA, 2013). Some studies suggest that mandated women are more likely to complete treatment than non-mandated women, a trend that strengthens in residential settings (Longinaker and Terplan, 2014).

Since 1996, cannabis legalization has expanded significantly, with 44 states and the District of Columbia enacting medical or recreational cannabis laws (DISA, 2024). Research has primarily focused on the impact of legalization on prevalence of cannabis use (Compton et al., 2017, Maxwell and Mendelson, 2016; O'Grady et al., 2022), emergency department visits (Maxwell and Mendelson, 2016; Shenn et al., 2019), risk perceptions (Carliner et al., 2017), and treatment admissions (Freeman et al., 2018), particularly among adolescent and adult populations. Notably, the enactment of medical cannabis laws has been associated with a 33.0% increase in treatment admissions for CUD among pregnant women (Meinhofer et al., 2019). The only study investigating the impact of cannabis policies on treatment outcomes for cannabis use among U.S. adults found no significant association between state cannabis policies and treatment completion (Bourdon et al., 2021). However, it did not specifically consider pregnancy as a factor in the analysis.

This study addresses aforementioned gaps by conducting a retrospective analysis of nationally-representative data of publicly funded residential treatment discharges in the U.S. to examine the association between cannabis legalization and treatment completion among pregnant women admitted to publicly-funded treatment programs for cannabis use from 2020 to 2022. We hypothesized that cannabis legalization would be a key factor associated with a higher likelihood of treatment completion, with differential impacts based on treatment settings and referral sources. This may be plausible due to reduced stigma, which could lower perceived risk and increase motivation for treatment, as well as enhance access to treatment resources. Findings from this study could inform public health strategies to improve cannabis use treatment engagement and completion among pregnant women, ultimately improving maternal and child health outcomes.