You have 2 querry we will come one by one.
The normal development of the baby is time bound, so doctor know the time to do USG what he want to see and what is expected that time .
AS in your case after two weeks viability of fetus wll be seen by fetal heart sound and visualisation of fetal pole
18 -20 Weeks of pregnancy
fetal anomaly scan to be done , so on.
Yes for injection .This is for support of placental .This will decrease the chances of pregnancy failure.
I think that you are satisfied with the answer. You are most welcome for further discussion .