Placenta praevia: Diagnosis and management

Placental development begins upon implantation of the blastocyst into the maternal endometrium during the initial stages of human embryogenesis. Implantation involves localisation to the most optimal position; most commonly the mid-to upper-anterior or posterior uterine wall. This physiological process can be defective and in approximately 6.3 per 1000 pregnancies (Health and Social Care Information Centre, 2007) the pathophysiological condition known as placenta praevia occurs.

Placenta praevia is characterised by either whole or partial implantation of the placenta in the lower uterine segment (Figure 1). Pregnancy complicated by placenta praevia or placenta accreta presents numerous and varied challenges for both the woman and her maternity care team due to the associated levels of maternal and fetal morbidity and significant demand on health resources (Royal College of Obstetricians and Gynaecologists (RCOG), 2011). When insertion of the placenta pervades the deciduas basilis and through the myometrium, a morbidly adherent placenta (placenta accreta) is indicated (RCOG, 2011). A continuous increase in the incidence of placenta praevia, including placenta accreta, is anticipated due to rising caesarean rates. It is suggested that the damage caused to the myometrium and endometrium due to surgical disruption of the uterine cavity during caesarean section is linked with an increased risk of placenta praevia in a subsequent pregnancy (Faiz and Ananth, 2003). More recent studies regarding risk factors for placenta praevia support this and additionally link placenta praevia to increased maternal age, multiple gestation, high parity and smoking (Gurol-Urganci et al, 2011).