When will you announce your pregnancy

Tunisia • Mother of 4 little princess & engaged 7.29.16
So yesterday my fiance & I we're talking about when is a good time to announce our 4th baby. With our youngest daughter he spilled the beans way to soon. I want to wait until I know what we're having (since we have 3 girls) I know everyone will be predicting the sex like last time. So when will you be announcing your pregnancy.