Would finding out your partner is infertile be a dealbreaker for your relationship ?

Not at all. Neither of us want children anyway, so to be honest...if it was discovered that she could not get pregnant it would be a tremendous blessing and relief because we'd not have to always take precautions anymore. But if we would've wanted children and then found out...it wouldn't change how I feel about her (I didn't marry her on whether or not she could have babies).