I'm going to lie to my mom about my significant other and I not being able to have kids.
Why would you lie to her about that?
I'm not interested in breeding. Why should my mom care anyway?
It will probably make her sad, though. It isn't cool to lie to your mom about anything, never mind something so important.
Whatever. It's my life, let's see how things go.
I really think you should reconsider. Just be honest with your mother and tell her you don't want kids.