Placenta Praevia

Question 1

Definitions of placenta praevia and low-lying placenta?

Answer 1

Placenta praevia = Placenta lies directly over the internal os

Low-lying placenta = placental edge lies <2cm from internal os

Question 2

Epidemiology of placenta praevia

Answer 2

Around 5% have low-lying placenta when scanned at 16-20wks

Incidence at delivery is lower at 0.5% - most placentas rise away

Question 3

Risk factors for placenta praevia?

Answer 3

Previous placenta praevia
Previous C-section
Multiple pregnancy
Multiparity
Smoking/drug use
Maternal age

Question 4

How does placenta praevia present? (after being identified on 20wk scan)

Answer 4

PAINLESS bleeding
Uterus non-tender
Lie/presentation may be abnormal

Question 5

How do you manage asymptomatic placenta praevia that has just been identified at 20wk scan?

Answer 5

• Advise to avoid having sex
• Reassure patient that most placentas rise away from cervix as you get closer to term and only 10% still have it at delivery
• Rescan at 32wks
  If still low-lying/praevia, rescan at 36wks

If still low-lying/praevia at 36wks
= Recommend elective C-section at 36-37wks

Question 6

How do you manage symptomatic placenta praevia? (i.e. presented to ED w/ painless bleeding)

Answer 6

ABCDE approach
IV access
Bloods (FBC, Rhesus, X match, clotting screen)
Continuous foetal monitoring (CTG)

Give anti-D immunoglobulin in Rhesus negative women

Decide on delivery:

If maternal/foetal compromise -> Class 1 emergency C-section

If no maternal/foetal compromise ->

• Admit to antenatal ward until bleeding stops, then observe for 48hrs
• Give IM steroids
• Re-scan at 36wks: if still praevia/low-lying, recommend elective C-section at 36-37wks

Question 7

Counsel a patient who has been diagnosed with placenta praevia on her 20wk scan

Answer 7

Explain importance of this finding:
Increased risk of bleeding

90% of placentas will move away from the os
Rescan at 32wks and go from there
Advise to avoid having sex

Question 8

Counsel a patient who has presented with bleeding due to placenta praevia

Answer 8

Explain that the bleeding is caused by the placenta praevia

Explain that we need to admit her until bleeding has stopped, then observe for a further 48hrs

Question 9

How do you classify placenta praevia?

Answer 9

I - placenta reaches lower segment but not the internal os
II - placenta reaches internal os but doesn’t cover it
III - placenta covers the internal os before dilation but not when dilated
IV (‘major’) - placenta completely covers the internal os