Check with your vet. If a male anytime from this point on. If a female BEfore her first her but not later than her 4th heat else it doesn't matter. Females spayed before their first are virtually assured 100% of AVOIDNG breast cancer. After their 4th heart the odss are the same whether spayed or not.
I've owned schnauzers for over 35 years. Love the breed, loved them all. I miss everyone of them who is no longer with us.