I've been there, I was so scared to tell my 9 year old that one day randomly in the possibly near future, she will bleed from her vagina! How is that an easy thing to bring up to your sweet young daughter??
I had to gear myself up, to talk to her about her first period. My husband was encouraging and offered to be be there for moral support, but I decided it was something I should do just her and I (at first anyhow) So I sat her down and recapped some of the discussions we had before about where babies come from etc. She looked suspicious already. I said "well honey, in order for women to have babies they have to have a period". Ahh I said it, she knows now and it was out...phew!
There were a few questions and obvious concerns, like will I bleed to death? How long do I bleed for? How will I know when it will come? Does it hurt? The best was...why don't boys get any stuff like this? I agreed the ratio of things that happen as your grow up isn't equally distributed between boys and girls but that was a conversation for another day.
I assured her it was going to be ok, I was there for her if she had questions, as well as her dad as he joined in the chat at the end. I told her we would prepare together and it wasn't something to be scared of or embarrassed about it happens to every girl around the world.
I felt better that I talked to her about this before the day was upon us, I feel like this has helped her prepare a bit more for the "day" and really as moms and parents this is all we can do for our kids. Give them the tools to excel and cope in life.
My sister told me once, change is inevitable so it's best to teach your kids how to cope with change early so they have an easier path in life and this advice has been very valuable.
So hopefully this helps any of your moms or dads out there with getting ready to have the chat with your daughters. They will be ok, and so will you.