For decades, public health advice around alcohol and pregnancy has focused almost entirely on women. The message has been clear: there is no known safe level of drinking during pregnancy, because alcohol can pass directly to the foetus and interfere with brain, facial and organ development.
That warning remains central. Maternal drinking is still considered the most direct and best-established risk factor for foetal alcohol spectrum disorders, a broad group of lifelong conditions that can affect learning, behaviour, speech, growth and physical development. But a growing body of research is now widening the lens. Scientists are increasingly examining whether a man’s drinking before conception may also leave a biological mark.
The idea is not that fathers expose a baby to alcohol in the same way a pregnant woman does. They do not. Instead, researchers are looking at whether alcohol can affect sperm before conception, altering biological signals that help guide early development after fertilisation.
A neglected side of reproduction
For years, reproduction research placed most responsibility on women’s bodies, habits and choices. That focus made sense in one respect: pregnancy takes place in the mother’s body, and substances in her bloodstream can reach the developing foetus. But it also left a major gap. The father contributes half of the genetic material, and sperm are not immune to environmental damage.
Recent observational studies have suggested that children of men who drank before conception may face a higher risk of some birth defects and developmental problems. In large population studies from China, paternal drinking before pregnancy was linked with increased rates of conditions including cleft palate and congenital heart defects. The overall risks remained low, but the association was strong enough for researchers to argue that future fathers should also be encouraged to reduce alcohol intake before trying for a baby.
The difficulty is proving cause. Human lives are messy. A man who drinks heavily may also smoke, eat poorly, sleep badly or be exposed to other risks. His partner may share some of those lifestyle patterns. Even careful studies cannot remove every possible explanation.
That is why animal research has become important. In controlled experiments with mice, researchers have been able to separate maternal and paternal alcohol exposure. Some results have been striking. When male mice were exposed to alcohol before mating, their offspring showed changes in growth, facial structure, brain organisation and motor behaviour, despite never being directly exposed to alcohol in the womb.
What sperm may carry
The most likely explanation involves epigenetics, the system that helps switch genes on and off without changing the DNA code itself. Alcohol appears capable of disrupting these chemical signals in sperm, including patterns of DNA methylation and RNA fragments that may influence early embryo development.
In simple terms, sperm may carry more than DNA. It may also carry information about the father’s recent environment, including exposure to alcohol. That information could affect how the embryo develops, how genes behave and how organs and tissues form.
Some mouse studies have also suggested that the effects may become stronger when both parents have been exposed to alcohol. Research has linked parental alcohol exposure with signs of altered foetal growth, changes in facial development and even markers of cellular ageing later in life. These findings are not proof that the same effects occur in humans in the same way, but they are enough to challenge the old assumption that only the mother’s drinking matters.
A shared responsibility, not a shift in blame
The new research should not be misread as an attempt to minimise the risks of drinking during pregnancy. Maternal alcohol exposure remains the clearest and most direct danger because alcohol can cross the placenta and reach the developing foetus. That biological pathway is well established.
What is changing is the understanding of responsibility. For too long, the burden of preconception and pregnancy health has fallen almost entirely on women. The emerging evidence suggests that men’s health before conception also deserves attention, not only because of possible biological effects on sperm, but also because a partner’s drinking can influence whether a pregnant woman continues to drink.
Researchers are not yet able to say exactly how much alcohol is safe for men before conception. The data are not strong enough for a precise threshold. But the direction of travel is becoming clearer: men planning to become fathers should treat the months before conception as part of the pregnancy health window, rather than as irrelevant.
That does not mean panic over a single drink. It means recognising that heavy or regular drinking before conception may not be harmless. Cutting back, improving diet, exercising, stopping smoking and taking general health seriously are no longer just lifestyle choices for prospective fathers. They may be part of giving a future child the best possible start.
The science is still developing, and much remains uncertain. But one message is already difficult to ignore: preparing for a healthy pregnancy should not be seen as the mother’s job alone.
With information from BBC
