It depends on several things. If it is possible to travel to your current school, then it is often possible to remain at the school after moving.
It also depends on the school authorities and the policies in place where you live. Every case needs to be considered separately to make sure you, as the student, are given the best opportunity for the remainder of the year.
12 weeks is considered the end of the first trimester.
6 months
Birth
at the end of the first trimester
always
Body parts are formed.
Body parts are formed.
Don't know if this counts for other schools, but mine has 5 classes per trimesters
1/3 pregnancies end in miscarriage.
At the end of the first Trimester (after 3 months)
Some people gain no weight during the first trimester, particularly if they have morning sickness. Other people gain a small amount, particularly towards the end of the first trimester. The most weight is gained during the second trimester though.
January is too late. you should transfer at the end of the semester so you'll have a clean slate when you move.