Complicated Placental Locations

Module by: Nicole Wade and Katherine Rabicki

Learning Objectives

  1. Define complicated placental locations​
  2. Identification on antenatal ultrasound​
  3. Preparing for and managing:​
  • Anterior placenta​
  • Low-lying placenta​
  • Placenta previa​
  • Placenta accreta​
  • Placenta with a succenturiate lobe (maybe)​


Complicated Placental Locations are defined as placental locations that add additional challenge to Caesarean section by way of increasing morbidity and mortality risk, often by way of severe hemorrhage.​


Some patients with complicated placental locations (i.e. placenta accreta spectrum) are best served at tertiary care centres able to provide specialized care. This module is not intended to encourage the full management of these disorders, but merely to provide background knowledge to help guide decision-making in rural/remote areas about when to transfer out.​

Antenatal Identification of Placental Location


  • Ideally sonography is used for antepartum identification of placental location​
  • Timing: Diagnosis of placenta previa or low-lying placenta should NOT be made <18 to 20 weeks GA, and provisional dx should be confirmed >32 weeks GA, or sooner if clinically warranted (SOGC Guideline 402).​
  • Method: Assessment by transvaginal ultrasound is recommended in all cases where placenta previa or a low-lying placenta is present or suspected by transabdominal sonography, with attempt to clearly define placental location (including laterality), characteristics of placental edge (including thickness, presence of a marginal sinus), and associated findings (succenturiate lobe, cord insertion close to the cervix) (SOGC Guideline 402).​
  • Further Imaging: Pregnant women with clinical risk factors for placenta accreta spectrum disorders and anterior placenta previa at the 18–20-week fetal anatomical ultrasound should be referred for specialist imaging to diagnose or exclude this disorder (SOGC Guideline 383).​

Painless antepartum bleeding

  • Antepartum bleeding, typically painless bleeding, should prompt investigation of possible abnormal placentation.​
  • No digital examinations antepartum until placental location is confirmed!
  • Visualization of placenta through the cervical os on speculum exam warrants immediate action.​

Heavy Bleeding in Labour

Williams describes attempting a vaginal exam in the OR with an emergency CS setup prepared to palpate the placenta (if NO ultrasound available)​


Anterior Placenta

Low-Lying Placenta and Placenta Previa

Placenta Accreta Syndromes


Next Section

Updated on February 16, 2022

Was this article helpful?

Related Articles