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Alcohol abuse increases the risk of unwanted pregnancy
Last reviewed: 03.08.2025
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A new study has found that among women with a strong desire to avoid pregnancy, those who drank heavily had a 50% higher risk of becoming pregnant than those who drank moderately or not at all. In contrast, participants who used cannabis had no higher risk of becoming pregnant than those who did not.
The study was published in the journal Addiction.
From a total sample of more than 2,000 non-pregnant women aged 15 to 34, the researchers identified a subgroup of 936 participants who did not want to become pregnant. In this subgroup, 429 women reported heavy alcohol use (based on a standard alcohol use questionnaire) and 362 reported cannabis use (including 157 who used it daily or almost daily).
Those who drank heavily and those who frequently used cannabis had, on average, a stronger desire to avoid pregnancy than participants who drank moderately or not at all and those who did not use cannabis.
Over the course of a year, 71 of the 936 women who wanted to avoid pregnancy actually became pregnant. More than half of the unwanted pregnancies (38) occurred in women who drank heavily – more than the combined number of pregnancies in those who drank moderately or did not drink. In other words, heavy drinking was associated with an increased risk of unwanted pregnancy compared with low levels of alcohol consumption.
In contrast, less than half of the 71 unintended pregnancies (28) occurred in participants who used cannabis, meaning that cannabis use did not increase the risk of unintended pregnancy compared with non-users.
Lead author Dr Sarah Reifman, from the University of California, San Francisco School of Medicine, comments:
"This study had two important findings. First, women who were not pregnant and who drank heavily were, on average, more likely to want to avoid pregnancy than those who drank moderately or not at all.
Second, heavy drinking, compared with moderate or no drinking, increases the risk of pregnancy within a year among those most anxious to avoid pregnancy. The next step in our research will be to find out why these pregnancies occur.
Meanwhile, given the potentially serious consequences of fetal alcohol syndrome (FASD) (which occurs when a fetus is exposed to alcohol during pregnancy) and the fact that the risk of FASD increases with the amount and duration of maternal alcohol consumption, it is imperative that doctors and clinicians support women who abuse alcohol to abstain from alcohol as soon as an unintended pregnancy is suspected."