Help please

So basically I'm 17 I wanted a baby and a few days ago I found out I'm around 7-8 weeks pregnant according to when I had my last period and I dunno how to tell my mum. I live with my mum boyfriend and sister but I'm so scared to tell her feel like she's gonna scream and shout and be angry and tell me to get rid of my baby I don't want to tell her in person, my first Scan is in 3 weeks. What's the best way to tell her other then person ?