FRCA Notes

Placenta praevia

Resources

  • Placenta praevia describes implantation of the placenta in the lower uterine segment, over or very near to the internal cervical os
  • It is typically diagnosed ante-natally on ultrasound, and is of relevance as it will necessitate LSCS unless the placenta is >2cm from the cervical os
  • Incidence 0.27 - 0.36%
    • Higher incidence in Asian populations (1.2%) although reasons for this not clear
Patient factors Uterine factors
Increased age (>40yrs) Uterine scar e.g. previous LSCS
Smoking Previous ToP
Assisted conception Previous praevia
Multiparous Endometrial scarring e.g. fibroids, endometritis, prev. MROP
Larger placenta e.g. twin pregnancy



Grade Description
1 Does not abut the internal os (low-lying)
2 Reaches margin of internal os (marginal)
3 Partially covers internal os (partial)
4 Completely covers internal os (complete)

  • This grading system can be simplified into:
    1. Marginal placenta praevia (70%); leading edge <2cm from internal os but not covering it
    2. Complete placenta praevia (30%); the placenta completely covers the internal cervical os

  • Typically diagnosed ante-natally during the foetal anomaly scan
  • 90% of those with a low-lying placenta resolve by the time of the third trimester due to placental migration

Clinical features

  • Patients may be asymptomatic
  • May present with painless ante-partum haemorrhage from 27 - 32 weeks
  • There may be associated abdominal pain in some cases
  • Although initial bleeding may be light and without maternal compromise, it can herald precipitous haemorrhage
  • Haemorrhagic shock may ensue

Associations


  • Consultant obstetrician and consultant anaesthetist-led care as higher risk of morbidity/mortality
  • Other MDT input may include neonatology, haematology, intensive care and interventional radiology
  • Delivery should take place in a centre where blood transfusion, caesarean section and critical care facilities are available ± other facilities such as IR
  • Elective caesarean section is generally indicated although some with marginal placenta praevia may be offered a trial of labour

Blood management

  • Additional wide-bore IV access
  • Consent for transfusion and cell salvage in advance
  • Cross-matched blood e.g. at least 2 units pRBCs, or more if coalescing PAS
  • Rapid transfuser and cell saver ready
  • Fluid warmer
  • TXA
  • Visco-elastic haemostatic assays

Anaesthetic considerations

  • Low threshold for arterial line
  • Regional anaesthesia is associated with reduced blood loss but patients may require GA and should be consented as such
  • Choice of anaesthetic depends on the clinical context
    • For elective LSCS, RA may be appropriate
    • For emergency LSCS, GA may well be required as well as management of major obstetric haemorrhage
  • Uterotonic plan discussed and ready to be administered

Post-operative care

  • Consider need for HDU-level care
  • Ongoing haemostatic resuscitation
  • Consider risk/benefit balance for chemical venous thromboprophylaxis
  • Analgesia as standard