Why is the limit for spontaneous abortion 20 weeks, what happens at 20th week? Why we define it as spontaneous abortion up to 20 week and why not after?
I feel like that may be because the limit of viability is at about 22 weeks, so it's easier to round to 20 weeks. So before 20 weeks, there's no chance of viability in the fetus, so it's a SAB. After 20 weeks, there's a chance of viability, so it becomes a stillbirth.