When it comes to having children later on in life, most women are well aware of the risks involved. Men usually are not.
Yet in spite of this disparity, a 40-year review of the medical literature has found that men also have "biological clocks", and that just like women, if these tick for too long, they can put the health of their partners and children at risk.
"While it is widely accepted that physiological changes that occur in women after 35 can affect conception, pregnancy and the health of the child, most men do not realise their advanced age can have a similar impact," says study author Gloria Bachmann, director of the Women's Health Institute at Rutgers University.
Bachmann and her colleagues noticed a downward trend in men past 45 - the age appeared to affect how long it took men to get their partners pregnant, and this was true even if their partner was much younger.
In cases where pregnancy was successful, the older male sperm was linked to more complications. One study, which followed the results of over 40 million live births for a decade, found that older fathers put the pregnant woman at higher risk of pre-eclampsia, gestational diabetes, and even premature birth.
As the child grows, so do the consequences. The same study found that children born to older fathers face an increased risk of newborn seizures, low birth weight and admission into the neonatal intensive care unit.
Other research has found links to congenital heart disease, birth defects, childhood cancer, and neurocognitive disorders, such as schizophrenia, autism and obsessive compulsive disorder.
Why this connection exists, we still don't know. While Bachmann and her colleagues think the blame lies with sperm degradation and semen quality, this is just a hunch and requires far more research.
"Although it is well documented that children of older fathers are more likely to be diagnosed with schizophrenia - one in 141 infants with fathers under 25 versus one in 47 with fathers over 50 - the reason is not well understood," explains Bachmann.
"Also, some studies have shown that the risk of autism starts to increase when the father is 30, plateaus after 40 and then increases again at 50."
It is clear that reproductive health is not simply a consideration for women, and yet all too often, the burden falls squarely on their shoulders. A simple Google search for "maternal age and pregnancy" will bring up roughly 65 million results. Swap 'maternal' with 'paternal', however, and you'll get nearly four times less information.
Even the reproductive division of the US Centres for Disease Control and Infection (CDC) seems to be focused solely on maternal and infant health, with no mention of paternal influence in these categories. In fact, the only recognition that a male counterpart exists whatsoever is a decade-old report on advancing male reproductive health, tucked at the bottom of the CDC web page.
"Perhaps this is rooted in the obvious role that women play in reproduction, leading us to perpetuate the idea that the topics of fertility, pregnancy and childbirth are women's issues, void of male involvement after their contribution of sperm," the authors suggest.
Whatever the reason, the fact that many men know little about this is cause for concern. Today, older men over the age of 45 are much more likely to have children than four decades ago, and yet few physicians talk to their male patients about fertility and the potential consequences of late fatherhood.
"Men, too, need to recognise their clicking biological clock," the authors write.
"Sperm banking for men who are delaying childbearing may need to be part of our societal responsibility commencing in the nearby future."
So if you're planning on waiting, or you just really aren't sure, maybe it's a good idea to make a deposit while you're young - or at the very least, before the age of 45. Otherwise, your reproductive clock will continue ticking silently away.
This study has been published in Maturitas.