You just say "Mom, I want to talk to you." Then she'll brace herself for what is coming next, and you just say it. Why, though, did you not think of problems like this when you made this baby? Condoms are everywhere.
Hi, Lillyann. Boy, that's going to be a hard thing to do, isn't it, honey? I would take her by the hand & tell her you need to talk with her. I would say, "Mom, I've got to tell you something that no mother of a teenager daughter wants to hear & I'm sorry that you're going to have to hear it." (And she may very well have figured it out by this time.) But, if not, I would continue with, "Mom, I'm going to have a baby," (as opposed to using the word pregnant. I think saying "baby" gives it a much more human touch. Now I'll explain to you a few reasons WHY she'll react the way she will & that might help you.
You must be really scared. My heart goes out to you. Your mother may be upset and disappointed, but you are her daughter. Hopefully, she will support you. It may be rough in the beginning, but it will get better. Do it now and get it over with. Good luck
Casually walk over to her,(Because if you don't you'll seem too nervous) And say: "Mom, have you ever wanted to be a grandmother?" Very suttle, and in 1-4 sec. she will realize what you are trying to say. Then, (optional) You could say "Look, I know this may be hard for you, but I am going to have this baby.
You are a adult, its nothing to be ashamed of. Hearing it from someone else, or her finding out later is going to hurt her moreso than you being a women about it, and telling her right away. She will be there for you, you just have to be honest with her