Unlike Alcohol, Cannabis Not Linked to Unwanted Pregnancy Risk

Study Design and Demographics

From a larger group of 2,015 participants, the researchers identified a subgroup of 936 women who expressed a strong desire to avoid pregnancy.  Participants regularly reported their substance use, pregnancy preferences (using the Desire to Avoid Pregnancy or DAP scale), and any pregnancies over the study period.

At baseline, 40% reported heavy drinking, 16% reported cannabis use, and 3% reported other drug use. Notably, both heavy drinkers and frequent cannabis users were more likely to express a higher desire to avoid pregnancy, compared to their non-using or moderate-use peers.

What the Study Uncovered About Pregnancy and Substance Use

Over the course of the study, 282 participants became pregnant.  Notably, 71 of these pregnancies occurred among individuals who had previously expressed a strong desire to avoid pregnancy.  Among this high-DAP group, over half of the pregnancies were linked to participants who reported heavy drinking at baseline.  Here’s how the numbers broke down:

Of the 71 pregnancies in the high-DAP group, over half (38) occurred among heavy drinkers.  In contrast, only 28 were among cannabis users, despite cannabis users also reporting a high desire to avoid pregnancy.  Other drug use was not statistically significant, likely due to the small sample size (3% reported use).

What the Data Says About Risk

This study offers a more nuanced view of substance use and reproductive outcomes than prior research.  Traditional studies have often relied on retrospective classifications of pregnancies as “intended” or “unintended,” which can be influenced by bias and social desirability.  In contrast, this study prospectively measured participants’ pregnancy preferences before conception occurred, allowing for a clearer picture of whether outcomes aligned with intentions.

Alcohol

The 50% increase in risk among heavy drinkers suggests that alcohol may disrupt not just decision-making in the moment, but broader reproductive planning efforts.  This finding underscores the need for clinicians to ask about alcohol use not only during pregnancy, but also during routine reproductive health visits.

Cannabis

While cannabis users showed a similarly high desire to avoid pregnancy, they did not show a statistically significant increase in undesired pregnancies.  This could reflect differences in how cannabis affects behavior, or in the kinds of people who use it.  Some studies even suggest cannabis may be associated with more cautious sexual behavior, though evidence remains limited.

Other Drug Use

The study could not draw firm conclusions about other illicit drug use due to the low sample size.  While trends suggested a possible relationship with pregnancy risk, further research with a larger user base is needed to confirm this.

Clinical and Public Health Implications

One of the most actionable takeaways is the apparent association between heavy drinking and an undesired pregnancy.  Healthcare providers may want to more proactively screen for alcohol use in patients who express a desire to avoid pregnancy and offer tailored interventions or counseling.

Dr. Sarah Raifman, the study’s lead author, emphasized the importance of continuing this research: “Finding out why those pregnancies happen is the next step in our research.”  She also underscored the public health risks of fetal alcohol spectrum disorders and the urgency of reducing alcohol use as early as possible during pregnancy, or ideally before.

A Balanced Perspective on Cannabis

Although cannabis was not linked to a higher risk of undesired pregnancy in this study, that doesn’t mean it is risk-free in pregnancy.  Previous research has explored the potential effects of prenatal cannabis exposure on fetal development and birth outcomes, and many medical bodies still urge caution.

At the same time, this study suggests that cannabis use should not be automatically equated with risky sexual behavior or lack of reproductive autonomy.  Instead, more nuanced public health messaging is warranted, especially as legalization continues to expand access.

Why These Findings Matter Now

These findings land at a pivotal time.  With more states liberalizing cannabis laws and debates intensifying around reproductive autonomy, public health strategies need to evolve.  The data suggest that risk messaging around alcohol use should be prioritized, especially for individuals actively seeking to avoid pregnancy.  Cannabis, on the other hand, may require more targeted, nuanced discussions, not broad-stroke warnings.