Abruptio Placenta and Placenta Previa

The major causes of antepartum hemorrhage include placenta previa, placental abruption, uterine rupture, and vasa previa. Placenta previa occurs when the placenta implants over the cervical os. This implantation may be marginal, partial, or total in its covering of the os. The incidence of placenta previa is 4.0 per 1000 pregnancies. Placental abruption refers to the complete or partial separation of the placenta from the uterine wall before delivery of the fetus. The incidence of placental abruption varies with the population studied 3–10 per 1000 pregnancies. Uterine rupture following previous vaginal delivery has an incidence of 0.18 per 1000 pregnancies. This increases significantly to 9 per 1000 pregnancies in women who have had a previous cesarean section. When fetal vessels have a velamentous insertion over the cervical os, the fetal vessels are not protected by the umbilical cord or the placenta. This is diagnosed as vasa previa and has a traditionally reported incidence of 1 in 2500 to 1 in 5000.