Grade 1 – (minor) the placenta is mainly in the upper part of the womb, but some extends to the lower part.
Grade 2 – (marginal) the placenta reaches the cervix, but doesn't cover it.
Grade 3 – (major) the placenta partially covers the cervix.
Grade 4 – (major) the placenta completely covers the cervix (most serious type of placenta praevia).
Anterior and upper segment means the baby is above the birth position but still not attached to the cervix...