When should I tell my daughter I’m pregnant?

Mel

My daughter is 5 (turns 6 in March 2020). I found out yesterday I’m pregnant with my second (3w5d). She’s always asked for a baby sibling but with my history of being high risk I didn’t necessarily plan to give her a sibling. Well I know she’d be over the moon knowing she has a baby brother or sister on the way. When should I tell her I’m pregnant? How do I explain to her what’s going on and answer all those questions she may have? Any ideas on fun ways to break the news to her. Thanks so much!