Heavy drinking, not cannabis, was tied to a sharp increase in unintended pregnancies—even among women actively trying to avoid them.
The study reveals a gap between intention and outcome that alcohol may be widening.
A Risky Link Between Alcohol and Unwanted Pregnancy
According to a new study, women who strongly wanted to avoid pregnancy were significantly more likely to become pregnant if they engaged in heavy drinking. Their risk was 50% higher compared to women who drank moderately or did not drink at all. On the other hand, cannabis use showed no connection to increased chances of undesired pregnancy. Women who used cannabis were just as likely to avoid pregnancy as those who didn’t use it.
The study began with a larger group of over 2,000 non-pregnant women between the ages of 15 and 34. From that group, researchers focused on 936 participants who expressed a clear desire not to get pregnant. Among them, 429 reported heavy alcohol use (based on a standard alcohol screening questionnaire), and 362 reported using cannabis. Of those cannabis users, 157 said they used it daily or almost daily.
Interestingly, both heavy drinkers and frequent cannabis users were more likely to report a stronger desire to avoid pregnancy compared to those who drank lightly or not at all, and those who didn’t use cannabis.
Heavy Drinking Drives Pregnancy Risk
Over the following year, 71 of the 936 women who were actively trying not to get pregnant ended up becoming pregnant. More than half of those unintended pregnancies (38) occurred in the group that drank heavily. That number exceeded the combined total among women who drank moderately or didn’t drink at all. The findings suggest that heavy alcohol use is clearly linked to a higher risk of undesired pregnancy when compared with lower or no alcohol consumption.
Cannabis Use Shows No Elevated Risk
In contrast, less than half of the 71 undesired pregnancies (28) occurred among people who used cannabis, meaning that those who used cannabis did not show an elevated risk of undesired pregnancy compared with people who did not use cannabis.
Lead author Dr. Sarah Raifman, of the University of California, San Francisco, School of Medicine, comments: “This study made two important findings. First, non-pregnant women who drink heavily appear, on average, to have a higher desire to avoid pregnancy than those who drink moderately or not at all. Second, drinking heavily as opposed to moderately or not at all appears to put those who most want to avoid pregnancy at higher risk of becoming pregnant within one year. Finding out why those pregnancies happen is the next step in our research.”
Health Implications and Medical Guidance
“In the meantime, given the potentially life-altering effects of fetal alcohol spectrum disorders (which occur when a fetus is exposed to alcohol through the mother’s drinking) and the fact that the risk of FASD increases with the amount and duration of the mother’s drinking, it’s important for doctors and clinicians to support women who drink heavily to stop drinking as soon as they suspect an unintentional pregnancy.”
Reference: “Alcohol and drug use and attainment of pregnancy preferences in the southwestern United States: A longitudinal cohort study” by Sarah Raifman, Sarah C. M. Roberts and Corinne H. Rocca, 30 July 2025, Addiction.
DOI: 10.1111/add.70135
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5 Comments
They did a study and discovered that women who drink heavily are at greater risk of having unintended pregnancies. Now they want to do additional investigational work to find out why. I think I know why.
I am retired from a different branch of the medical profession but could have told you about these findings for free !!
Do these researchers have NO common sense.What awaste of time and money
This is exactly the kind of useless and wasteful research that I hope is being cut from the NIH budget.
Someone actually funded a study to find this out? W_F
The study’s results are hardly surprising. So women who are frequently inebriated are at increased risk of unintended pregnancies. But the idea that they want to do further research to find out why is utterly comical. This isn’t rocket science. I had to read the article twice to make sure I wasn’t missing something. SMH.