Hi Mair,
So sorry for your loss.
I started to use mine just like normal when i got my
af again (it did say though day 99 on it when i turned it on, lol). Keep in mind however, that there is no such thing as normal (for the vast majority of women) after a mc and the cbfm might therefore ask for more or less sticks due to this (as your cycles might change in every conceivable way, lenght, cramps, flow etc.)
Anywhoo, its a clever little machine and will change accordingly and should you have any probs always check the website faqs page. The general advice is to wait at least 2 months. I didnt but i did check my
hcg levels to get a negative
hpt before i tried again as obviously i wouldnt ov until the hormones were out of my body (in which case you can use the cbfm no probs

)
Good luck!!
