Learning objectives

• Description of placenta praevia
• Management of placenta praevia

Definition and mechanisms

• When the placenta attaches inside the uterus near or over the cervical opening
• Classified as a complication of pregnancy
• Commonly occurs around 32 weeks of gestation, however, placenta praevia should be suspected if there is bleeding after 24 weeks of gestation
• Affects approximately 0.5% of pregnancies
• A caesarean section is often required because of the high bleeding risk
• The cause is unknown, however, is thought to be related to abnormal vascularisation of the endometrium caused by scarring or atrophy from previous trauma, surgery, or infection

Classification

• Minor
  • Placenta is in the lower uterine segment, but the lower edge does not cover the internal os
• Major
  • Placenta is in the lower uterine segment, and the lower edge covers the internal os
• Other than that placenta previa can also be classified as:
  • Complete: 
    • The placenta completely covers the cervix, blocking the vagina
  • Partial: 
    • The placenta partially covers the cervix
  • Marginal: 
    • Placenta is positioned at the edge of the cervix
    • Touching but not covering the cervix
    • More likely to resolve on its own

Complications

Risk factors

• Previous placenta previa, caesarean delivery, myomectomy, or endometrium damage caused by dilation and curettage
• Younger than 20 or older than 35 
• Multiparity
• Smoking or cocaine use during pregnancy
• Pregnant with twins, triplets, or more
• Previous surgery on the uterus
• History of uterine fibroids

Diagnosis

• Ultrasound

Management

Suggested reading

• Pollard BJ, Kitchen, G. Handbook of Clinical Anaesthesia. Fourth Edition. CRC Press. 2018. 978-1-4987-6289-2.
• Plaat F, shonfeldd A. 2015. Major obstetric hemorrhage. BJA education. 15;4:190-193.
• Walfish, M., Neuman, A., Wlody, D., 2009. Maternal haemorrhage. British Journal of Anaesthesia 103, i47–i56.