Answer: The placenta is an organ within the uterus (womb) through which the unborn baby gets nutrients (food) and oxygen, as well as removing waste products. It is attached to the wall of the uterus by many blood vessels. Normally, the position of the placenta will move as the womb grows and stretches, so that eventually, by the last three months of pregnancy, it should be near the top of the womb. In some cases however, (one in 200 pregnancies) the placenta stays in the lower portion (part) of the womb, and either partially or completely covers the cervix (neck of the womb). This is known as placenta praevia. Placenta praevia occurs in four grades, ranging from minor to major: Grade 0 - normal growth 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).