As a society, we put a significant emphasis on women’s health both immediately prior to and during pregnancy – and rightly so. A woman needs to prepare her body for the arduous nine months of gestation ahead to give the growing baby the best possible start to life.
A pregnant woman is likely to take supplements and maintain a healthy diet free of alcohol and cigarettes while protecting herself from unnecessary environmental toxin exposure. In comparison, men’s health prior to conception is relatively insignificant right? Wrong!
Our research shows that male diet prior to conception – particularly a fast-food-based diet – can be significantly detrimental to pregnancy success. Using an animal model of diet-induced obesity, we compared pregnancy outcomes when fathers were either normal weight or obese.
We found that rates of pregnancy were significantly lower when the father was obese because embryos generated with sperm from obese males weren’t very good and failed to implant into the mother’s uterus.
When obese fathers were able to achieve a pregnancy, the resulting foetus and placenta were both smaller than normal and the foetus was developmentally delayed. As the theory of the developmental origins of health and disease suggests, these small-for-gestational-age foetuses are at a higher risk of disease in later life, including cardiovascular disease, type 2 diabetes and high blood pressure.
Indeed, our data indicate that being an obese male could significantly compromise the health of the resultant offspring. Initial studies in humans have also shown that the time taken to become pregnant is significantly longer if the father is obese, and IVF embryos are of poorer quality.
This is of particular concern given the rising rates of global obesity.
And bad diet isn’t the only vice of modern man that can affect not only his fertility but also the health of his offspring. Almost 20% of Australian adult males smoke despite its well-publicised health risks. Studies from China, Australia and Europe have identified an approximately 30% increase in the rate of childhood cancers when fathers smoke prior to conception.
In particular, the rate of leukaemia, lymphoma and brain tumours were up to 80% higher in children under the age of five when fathers had smoked prior to conception, even though mothers were non-smokers. And the rate of childhood cancer was highest when fathers smoked more cigarettes per day, had been smoking for a longer time, and started smoking before the age of 20.
What’s more, passive smoke exposure of mothers around the time of conception – likely due to fathers’ smoking – is associated with a significantly higher incidence of serious congenital heart defects in infants.
The effect of fathers' alcohol consumption on offspring health is harder to define because of conflicting reports. It’s been suggested that a father’s alcohol consumption prior to conception results in a significant reduction in foetal birth weight, but this is yet to be conclusively proven and is subject to a number of confounding factors.
Animal models have shown fathers' alcohol consumption to be associated with increased malformations, growth retardation, and behavioural anomalies in offspring, although alcohol exposure in these cases is reasonably high. So any adverse effects of paternal preconception alcohol exposure may be more subtle than this.
The dangers of work
While the effects of paternal diet, smoking, and alcohol consumption on offspring health can be mitigated with appropriate lifestyle changes before starting a family, occupational toxin exposure is harder to avoid.
A recent study involving almost 10,000 children with birth defects was able to relate the rate of foetal malformation to job types their fathers did. Overwhelmingly, fathers exposed to solvents and chemicals in the workplace, such as artists, cleaners, hairdressers, scientists, welders, metal and food processing workers have significantly higher rates of a variety of birth defects among their offspring.
And several paternal occupations such as office jobs and law enforcement were associated with significantly reduced rates of foetal birth defects. But avoiding occupational exposure to reproductive toxicants when planning to start a family is another question altogether. As a society, we really need to know what is bad for sperm.
Passing it on
Damage or changes to the male germ line, the sperm, is how paternal lifestyle and occupation end up having a detrimental effect on foetal development and offspring health. Sperm are particularly vulnerable to oxidative stress, which can damage DNA. And both a high-fat diet and smoking have been associated with increasing levels of oxidative stress.
Fathers' health prior to conception is clearly just as important as mothers', and when thinking of starting a family both mum and dad need to be as healthy as possible.