Telling my parents I'm pregnant

How to tell my parents that we are expecting. My mom had been telling me not to get pregnant because we already have 3 kids and we should just focus on our 3 kids. Mind you I am grown women. I am around my 30's, married and have our own place. But she is really not going to like this pregnancy announcement. I know she just looking for our best interest but really we are okay financially and we are happy. Any ideas on how to break this unhappy news but we are happy about the baby. It's assume that I have to go through this stress.