How to tell mother about pregnancy

I’m currently 6 weeks and really wanting to tell my family that I’m pregnant, but I am really scared of my mothers reaction. She isn’t the biggest fan of my fiancé and I know she thinks I shouldn’t be having a baby right now as she mentions birth control almost every time I see her. I have 2 older sisters that aren’t having babies any time soon and so I know she would eventually be excited that shes going to be a grandma, but how do I get over the initial announcement and her possibly not being happy about it? Her opinion means everything to me and it will really hurt me if she isn’t happy about it and I don’t know how to prepare myself for that.