What is "placenta praevia"

alt. (context pathology English) A complication of pregnancy in which the placenta is inserted partially or completely in the lower segment of the uterus (above the opening of the cervix). n. (context pathology English) A complication of pregnancy in which the placenta is inserted partially or completely in the lower segment of the uterus (above the opening of the cervix).

Placenta previa is an obstetric complication in which the placenta is inserted partially or wholly in the lower uterine segment. It is a leading cause of antepartum haemorrhage ( vaginal bleeding). It affects approximately 0.4-0.5% of all labours.

In the last trimester of pregnancy the isthmus of the uterus unfolds and forms the lower segment. In a typical pregnancy the placenta does not overlie. If the placenta does overlie the lower segment, as is the case with placenta previa, it may shear off and a small section may bleed.