Research presented this week at the annual meeting of the European Society of Human Reproduction and Embryology in Rome suggests that men whose mothers had several alcohol drinks per week during pregnancy may have lower quality sperm. The study, conducted by researchers from the University of Aarhus in Denmark, studied 347 men born between 1984 and 1987. All of their mothers were participants in a “Healthy Habits for Two” study, for which they completed questionnaires about their medical history, health habits and lifestyle during the 36th week of pregnancy. Two decades later, researchers collected blood and semen samples from their now-grown sons.
Researchers divided the men into four categories based on their mothers’ alcohol consumption — those who didn’t drink at all, those who consumed 1 to 1.5 drinks per week, those who had 2 -4 drinks per week, and those who had 4.5 drinks or more. A drink was defined as 12 grams of alcohol — the equivalent of 11 oz. of beer (a little less than one can), 4 oz. of wine or 1.4 oz. of liquor.
After controlling for factors such as smoking and health history in the sons, researchers found that, on average, men whose mothers drank 4.5 or more drinks per week during pregnancy had 32% lower sperm concentration compared with men whose mothers didn’t drink at all. But they also noted that sons of women who had about one drink per week had the highest sperm count and semen volume of all four groups. The researchers also compared fathers’ drinking habits with their sons’ sperm counts, and noted no correlation.
Of course, as Allan Pacey, a senior lecturer in andrology at the U.K.’s University of Sheffield, pointed out to the BBC, while the study raises questions about the relationship between prenatal alcohol exposure and developmental complications impacting male fertility, it isn’t entirely clear that the link between routine alcohol consumption during pregnancy and lower semen quality is direct. As he explains to the BBC:
“I don’t think we can be certain that alcohol is necessarily the bad thing here — it could be a surrogate marker for something else — but clearly there is some kind of relationship.”
In other words, could it be, for example, that women who drink during pregnancy might be more likely to expose their sons to other potential hazards — or be exposed to such hazards themselves — that could impact testicle development or fertility? Whatever the missing dots in the connection between lower sperm count and maternal alcohol consumption during pregnancy, the researchers are hopeful this initial study opens the door for future research and a better understanding of the factors that influence the quality of semen. As study author Dr. Cecilia Ramlau-Hansen concludes:
“If further research shows that maternal alcohol consumption is a cause of reduced semen concentration in male offspring, then we are a bit closer to an explanation of why semen quality may have decreased during the last decades and why it differs between populations.”