Is there a link between mumps in childhood and male infertility?

Maybe it's a domestic myth, but is there any proven link between boys contracting mumps in infancy and male-infertility later in life?

Look dear,
Yes there is a strong relationship between contracting mumps in childhood & infertility as a complications of the mumps virus.
Mumps may cause orchitis & the testis may undergo atrophy,usually unilateral,but may be bilateral causing sterility.
In the female it may also cause oophoritis,but it's of less incidence than orchitis.
Believe me dear,I'm a student in faculty of medicine 5th year & I studied it several times.
I hope I could help.

The way I heard it was that if a male contracted mumps later in life there was a possibility that it could cause infertility - this may have been a myth as well.

There is a condition called orchitis which sometimes develops after mumps which can cause infertility. It is rare in boys under 10 but the likelihood increases with age. If properly treated loss of fertility is usually avoided.

Yes it's a myth. There's no link between childhood mumps and male sterility. There is, however, a direct link between mumps in the postpubescent male and possible sterility. In the postpubescent male, mumps can lead to complications such as mumps-induced orchitis, an inflammation of one of the testes. About half the men with mumps-induced orchitis suffer some atrophy of the testicles, but because the condition is usually unilateral (one-sided) it rarely results in sterility.