Women who drink alcohol during pregnancy are more likely to have children who grow up vulnerable to alcohol dependence, a major study suggests.
University of Wisconsin-Madison researchers Mary Schneider and Alexander Converse found that prenatal exposure to alcohol – and, to a lesser extent, stress – can leave lasting changes in the brain’s reward circuitry, shaping drinking behaviour decades later.
In the study, pregnant rhesus monkeys – chosen as they are genetically and biologically closer to humans than other lab animals – were assigned to one of three groups: some consumed moderate amounts of alcohol, others were exposed to mild, repeated stress, and a third group experienced both.
The scientists then followed the offspring into adulthood before measuring changes in their brain chemistry and observing how they behaved when given access to alcohol.
The results pointed to a clear and enduring impact on the dopamine system – the network involved in reward, motivation and pleasure.
Both prenatal alcohol exposure and prenatal stress altered dopamine function in the adult monkeys.
But the effects were most striking in the offspring exposed to alcohol in the womb.
When offered alcohol as adults, they drank more quickly than other monkeys, suggesting a shift toward riskier patterns of consumption.
In the study, the adult offspring of mothers who drank during pregnancy showed altered brain chemistry and a telling behavioral change: they drank alcohol more rapidly when it was offered (stock)
Crucially, the researchers found they could spot differences in the monkeys’ brain reward system before the offspring had ever touched alcohol – and those differences helped predict how they would drink later.
Once the monkeys started drinking, alcohol appeared to change the brain further, creating a reinforcing cycle between what was happening in the brain and how they behaved.
The researchers say prenatal alcohol exposure led to long-lasting changes in the brain systems involved in reward and motivation.
While scientists still don’t fully understand exactly how alcohol in the womb causes these effects, the changes were still visible in adulthood – years before the animals ever took their first sip.
When given access to alcohol later on, monkeys exposed during pregnancy went on to drink more quickly, suggesting they were more drawn to alcohol or less able to regulate their intake.
Overall, the findings support the idea that a person’s vulnerability to problem drinking can be shaped before birth, creating differences in the brain that may influence drinking habits later in life.
The team, writing in the Journal of Neuroscience, suggests this may help explain why some people can drink casually, while others find it harder to stay in control – because their brains may react and adjust to alcohol in different ways once they start drinking.
In some individuals, these unique brain changes are harmful. Instead of just feeling the effects of alcohol, their brain’s reward and motivation systems get hijacked.
Drinking alcohol during pregnancy causes permanent birth defects and cognitive disabilities, known as Fetal Alcohol Spectrum Disorders (FASD), as the alcohol disrupts fetal development (stock)
These changes may make a person more likely to crave alcohol, need more to feel the same effects, or feel worse when they stop drinking.
While the study did not find that prenatal stress alone increased drinking, the authors say it could still raise the risk of other emotional or behavioural problems later in life.
Researchers used rhesus monkeys because their biology, social behaviour and patterns of voluntary drinking closely resemble humans – making the findings more relevant than studies in rodents.
Alcohol triggers a chemical ‘reward hit’ in the brain, which can feel relaxing or pleasurable at first. But with repeated drinking, the brain can start to adjust in ways that backfire – producing less of its own natural reward signals and relying more heavily on alcohol to feel good.
Over time, everyday pleasures can feel less satisfying, while alcohol becomes more appealing. In some cases, the brain begins to treat drinking as a priority, which is one reason controlled use can tip into compulsive behaviour and addiction.
Separately, research has long shown that drinking during pregnancy can cause lifelong harm to a developing baby, including a range of permanent physical, behavioural and learning difficulties known as fetal alcohol syndrome (FAS).
Alcohol passes through the placenta, disrupting development at crucial stages. This can lead to growth problems, distinct facial features, organ damage and lasting effects on the brain, including learning difficulties, poor memory, attention problems and impaired judgement.
There is no known safe amount, type or time to drink alcohol during pregnancy, which is why health authorities recommend avoiding alcohol completely.
