If maternity and paternity leave is leave without pay (unless one elects or has to use available accrued paid time off) then it shouldn't matter. Except having to plan around a short term vacancy can be an undesirable problem for a manager or company No matter the position goes vacant for that period of time or if a temp worker is hired to fill it, you will have a loss in productivity.
If maternity and paternity leave is without pay it's still advantageous for the company to hire men over women, as they will have to hire temps more often on average for maternity leave with a women over a man.
And temps generally are worse productivity-wise than an experienced worker.
