From the MacMillan Guide to Family Health 1982:
"[...] A fairly common risk of mumps is the swelling of testes in a boy or the ovaries in a girl. This is much more common in an adult. Invariably the swelling goes down after a few days leaving no ill effects. It is excessively rare for the swelling to cause sterility. A rare complication is acute pancreatitis which passes within a few days. Mumps is generally a mild disease. The usual outcome is complete recovery within about 10 days"
Well, postpubertal mumps leads to orchitis in about 25% of cases, with perhaps half of those causing testicular atrophy. I suppose it's a dusky path in the hodology of the (sensible) "would you expose" question, but I don't know that it warrants a stock response, especially as a real rather than speculative threat to fertility.