The simple answer is that we need much more research to find out why this decline in sperm count is happening.
We cannot be complacent about the potential negative effect on fertility and must now urgently rally to substantially increase the research effort into male reproductive health.
Also, although the prevailing evidence shows a decline in reproductive health, not all studies show this; there are some geographical differences.
It will be critical to determine what the key differences between geographical regions are – such as genetic differences and exposure to specific pollutants – so we can then examine treatment strategies to limit these negative effects.
If it’s the foetus that is mainly affected, what can the adult man do?
Even in adults, exposure to chemicals, such as bisphenol A, which are thought to affect fertility, can have a negative effect, so men should limit their exposure to toxic chemicals.
This includes stopping cigarette smoking.
Also, a healthy lifestyle is very important as there is a known link between obesity and reduced sperm count.
By Chris Barratt- Professor of Reproductive Medicine, University of Dundee.
This article was first published by The Conversation