Hi I am not really sure but would love to know as well. I asked the nurse at the clinic today, she said no. She did not give me a clear answer though and just said your cycle will not be the same and you shouldn't count it as day 1. But she was also just trying to tell me not to try at all until I have my first af which I don't think I can listen to. I believe the correct answer is that cd 1 is technically the first day that your hcg levels drop down to 0. But in reality most women might not be able to pinpoint this. My levels dropped drastically today from monday when my miscarriage started and I'm positive they will be at 0 by the weekend so I will likely choose sat or sun as cd1 just so I have something to go by.