Older men are more likely to have children born prematurely, a study in the USA has found, while their partners are at higher risk of developing gestational diabetes.
In the study of 40 million births, babies of fathers older than 45 had a 14 percent higher chance of being born prematurely than those with younger fathers. The authors also investigated the impact of fathers' ages on their partners' health during pregnancy.
When looking at birth risks, the age and health of the mother is often the focus, but 'having a healthy baby is a team sport and the father's age contributes to the baby's health too', said Dr Michael Eisenberg from Stanford University Medical Centre, California, and a senior author of the study.
The research, published in the BMJ, analysed all documented live births in the USA between 2007 and 2016. The authors considered a range of factors, from birth weight to likelihood of seizures, in order to determine the babies' health. After adjusting for other causes – such as maternal age, race and education – the team found that the older fathers were associated with worse outcomes, such as premature birth.
As well as an increased chance of premature birth, babies born to older fathers were also more likely to need treatment in intensive care, have a lower birth weight and score lower on a test of overall health.
The study found that women who had children with older men were more likely to develop gestational diabetes, regardless of their own age. For mothers with the oldest partners, of 55 years and over, the odds of developing gestational diabetes were 34 percent higher. Dr Eisenberg described this finding as 'surprising'.
The exact mechanisms of this are still unknown, as the study did not address cause and effect. However, the authors suggested there could be genetic changes in the sperm of older men that result in larger placentas, which have been linked to gestational diabetes.
The odds of the mother developing other conditions such as pre-eclampsia and eclampsia were also investigated, but the results were not statistically significant.
Writing in a commentary alongside the BMJ article, Dr Hilary Brown, a perinatal epidemiologist at the University of Toronto, Canada, who was not involved in the study, said that the findings of this study highlight the 'importance of including men in preconception healthcare'. As a result, changes to public health messaging 'may be needed', she said.
Further investigation is needed to determine the impact on public health, but both Dr Eisenberg and Dr Brown stressed that the overall risk of adverse outcomes remains low – although this risk will increase as the prevalence of older fathers increases.
The research builds on an earlier study from 2017 – published in Human Reproduction – in which Dr Eisenberg showed that the average age of fathers was indeed increasing, with fathers over the age of 40 now accounting for 9 percent of all births.