How to tell your boss and when?!

Ashley • a happy little Ma
I just started a new job, that I LOVE, beginning of Oct. The Monday right after finding out on Friday that we are pregnant. Around the first of January should mark my 90 days and I should be hired in with benefits. They love me so far, I'm a great worker, it's mostly women and they treat everyone like family. I figured I should wait until my 90 day mark to tell them, so they don't doubt hiring me in. Do you agree? & also how should I share with them my news, any ideas? Would really love to hear opinions from those who've gone through this before, as I don't really have anyone to ask who's experienced this decision! Thanks! <3