Need Advice: Should I tell my boss this week?

Jessica
Need some advice: Should I tell my boss I'm pregnant this week?
I'm only 9 weeks along but my boss is going on Maternity leave at the end of this week and won't be back until February 2017. She will be doing some occasional work from home and I will probably speak with her every once in a while. 
Part of me would like to tell her in person, but I also don't want to give her something to worry about right before she has her baby. 
I can either tell her now in person, or call her in a few weeks to tell her over the phone. 
Some background: we do not hang out outside of work, but I would say we are close work friends. We talk to each other quite a bit about our lives and exchange small birthday and Christmas presents and such. 
What do you all think? Advice would be greatly appreciated!!