Potential harms include neurodevelopmental impairments as well as particular facial features most commonly associated with foetal alcohol spectrum disorders (FASD), but also behavioural, cognitive and learning problems, such as speech delays.

The effects cover a broad spectrum, which is part of why FASD is now the preferred description to "foetal alcohol syndrome", or FAS.

The idea that a father s alcohol consumption before conception could have an impact on the offspring may seem far-fetched. But recent population studies have found that babies whose fathers drank are at a higher risk for various poor health outcomes.

For more than 50 years, scientists have warned about the risks of drinking alcohol in pregnancy. Recent research has found that a mother s consumption of as little as one drink a week may affect a child s brain development, cognitive function and behaviour, and facial shape, while for decades, public health campaigns have repeatedly said that there s no safe amount of alcohol for mums to drink while pregnant.

One 2021 observational study of more than half a million couples in China, for example, found that the risk of birth defects – including cleft palate, congenital heart disease, and digestive tract anomalies – was higher if the father drank before conception, even when the mother did not drink. Another population study from China compared 5,000 children with congenital heart defects to 5,000 without. Again, while overall risk remained relatively low, it found that babies were nearly three times more likely to have a congenital heart defect if their father drank – defined as having more than 50ml (1.7fl oz) of alcohol per day in the three months before pregnancy – than if he didn t.

Research on fertility and reproduction "has been so woman-focused, so maternal centric, that we ve not really done our due diligence on the male side", says Michael Golding, a developmental physiologist at Texas A&M University who researches alcohol exposure and foetal development.

Yet researchers like Golding have suspected a paternal role for a long time. "For years now, we ve been hearing stories from women who said,  I never drank during pregnancy, but now I have an FAS kid – and my male partner was a chronic alcohol abuser ," he says. But such stories often were dismissed as mothers being forgetful, if not outright lying.

It s important to note that the overall risk of birth defects still remained relatively low. In the 2021 study of various birth defects in China, for example, the most-impacted type – cleft palate – was found in just 105 babies of the 164,151 whose fathers drank. But this made cleft palate 1.5 times more likely among offspring of fathers who drank, than if the fathers didn t drink. "Our finding suggests that future fathers should be encouraged to modify their alcohol intake before conceiving to reduce foetal risk, considering a paternal drinking rate of 31.0% substantially elevated the risk of birth defects," the researchers wrote.

In July 2024, meanwhile, a study found that if fathers drank alcohol before conception, foetal growth appeared to be impacted.

Still, pinpointing whether the father s alcohol consumption actually caused these issues, as opposed to just being correlated with them, is difficult. While researchers of both studies controlled for confounding factors, such as if the father also smoked, it isn t possible to account for every single potential contributor. "Human studies are extremely messy – there are a lot of confounding factors there," says Golding. "What is the individual s diet? Do they exercise? There are a whole bunch of things there that make it incredibly difficult."

Golding s team also found that the face shape of a mouse changed according to how much alcohol it s father had consumed. "The take-home message… is that male alcohol use is not going to have a yes/no impact on children; it will have graded effects where the more a man drinks, the worse the outcomes," he says.

Golding isn t the only researcher to find a link between paternal alcohol consumption and FASD-like outcomes in mice. Other studies have found that the offspring of alcohol-exposed male mice are more likely to show foetal growth restriction, metabolic defects and various differences in genetic expression, compared with mice that were not given alcohol. At University of California Riverside, Kelly Huffman, a psychology professor with a background in developmental neuroscience, has been running experiments that have also found that the mouse offspring of alcohol-exposed dads are more likely to show certain outcomes.

While the exact impact of paternal drinking has yet to be teased out, researchers agree on one thing.

"There s this enormous burden that s put on women," says Golding. "But male health is important to foetal development. There is a responsibility of both parties here to support and provide for the health of the baby."