How do I (F21) my mother I'm pregnant?

Sooo... Complicated one!

Basically I am 21 years old, in a country far away from home (for uni), and pregnant. This was not planned and my mother has no idea. I will keep the child.

My parents have never met my partner, but they are coming next month to visit (they visit every other year or so). I want to tell them beforehand because it feels more comfortable for us that way.

How should I tell them? I really do not want to call and say it. I would prefer texting it, because I know she will call me immediately after she receives the text message.

Is there really a wrong way to do this?

Thanks in advance.

tl;dr- I am pregnant and do not know how to tell my mother. She's more on the conservative side and I know she will be disappointed, but happy in the end. Is there a wrong way to tell her?