Is My Blue Pitt Old Enough To Produce Mature Sperm To Get My Female Blue Pitt Who Is In Her 1st Heat Pregnant?

Haze (our female) is 10 months old and in her first heat. We try to keep her and steel (our male who is 8 months old) apart. They've managed to lock up 2 times. Shes been in heat about a week and a half maybe two. Is he mature enough to produce mature sperm to get her pregnant? And if she is pregnant, could this kill her? They are two beautiful nice looking blue pitts, but were not ready for them to have pups yet. What should I do?