hearing the heart beat, seeing your baby ultrasound for the first time, or first movements. with my son, it was the 1st 2 but with my daughter it was definitely the first movements, I've had 2 miscarriages since my son was born & pregnant now with my daughter, it didn't feel safe to believe or think it was real til I could start to feel her move
It became real for me when I finally started feeling movements!