Time frames

I guess I'm back posting again because i have nowhere else to turn

For those who have had MMC, how long after finding out did it take your body to cotton on and begin the process? (If you're comfortable sharing)

Going off measurements HB has stopped at some point of the last 5/6 days.

I'm booked in for surgical management for next week, and I'm terrifed it may happen at home beforehand, it's my first MMC but 4th loss as a whole over the last two years and I really don't know what to expect this time. The previous times, the process was just happening so I kinda new. But I feel lost on this one.

I have been taking progesterone pessaries for the last month if that makes any difference?