Heavy Drinking, Not Cannabis, Was Linked to Unintended Pregnancy Among Those Wanting to Avoid It

In a longitudinal cohort of 2,015 individuals capable of pregnancy, heavy drinking and daily cannabis use were associated with higher desire to avoid pregnancy. Among those with high desire to avoid pregnancy, heavy drinking was associated with 51% higher pregnancy risk (aHR 1.51, 95% CI 1.12-2.04). Cannabis use was not associated with elevated pregnancy risk among those wanting to avoid it. Other drug use was not associated with pregnancy regardless of preferences.

Longitudinal cohort study of 2,015 individuals ages 15-34 from 23 healthcare facilities in five southwestern U.S. states (2019-2022). Past-month substance use self-reported at baseline. Pregnancy preferences measured quarterly using the Desire to Avoid Pregnancy scale. Incident pregnancy reported every 6 weeks. Adjusted mixed effects regression and Cox proportional hazard models used.

This study addresses a long-standing assumption that substance use leads to unintended pregnancy. The nuanced finding that heavy drinking specifically, and not cannabis or other drug use, is associated with unintended pregnancy in those wanting to avoid it suggests targeted interventions should focus on alcohol rather than substance use broadly.

Substance use and unintended pregnancy are often discussed together as a generalized risk, but this study shows the relationship is substance-specific. The finding that cannabis use did not increase unintended pregnancy risk challenges assumptions that may drive stigmatizing clinical practices.

Self-reported substance use may underestimate actual consumption. Only baseline substance use measured. Five southwestern states may not represent national patterns. Cannot determine mechanisms (e.g., whether alcohol affects contraceptive use or judgment).