Prehaps wait untill you have seen your little baby on your dating scan usually 12-13 week :-)
I would wait until you are out of your first trimester. Around 12-13 weeks
12-43 months would be a very long time to wait ;-) hehe... all kidding aside I'd say around 12-13weeks since at her age it'll be hard to explain if anything were to happen to the pregnancy
I told my girls that are 5 and 7, when I was 4 months just to be on the safe side. Congrats and good luck :)
Meant 2-3 months lol oops!