I always thought that women go thru IVF because they cannot conceive naturally.
I never knew that it could be because of their male partner's infertility and so this was News to me.
Male infertility is behind one in three IVF cycles
This article states that men can improve their chances of fathering a baby if they maintain a healthy lifestyle with good diet and exercise (as chronic diseases like diabetes and obesity can reduce their fertility), they don't indulge in smoking, drugs and alcohol, have no STIs (gonorrhea, chlamydia) and plan to have children early in their life i.e. before the age of 40.