8.20 Placenta Previa

Question 1

What is the RCOG definition of a low-lying placenta and placenta previa?

Answer 1

placenta within 20mm of the internal cervical os

previa is when it is over the os

(about 1% of pregnancies)

Question 2

What are 3 causes of antepartum haemorrhage?

Answer 2

• placenta previa
• placental abruption
• vasa previa

Question 3

What are the risks of placenta previa?

Answer 3

• APH
• emergency c-section
• emergency hysterectomy
• anaemia and transfusions
• preterm and low birth weight
• stillbirth

Question 4

RCOG dont recommend using the four grades of placenta previa but what are they?

Answer 4

Minor praevia, or grade I
– placenta is in lower uterus but not reaching the internal cervical os

Marginal praevia, or grade II
– placenta is reaching, but not covering, the internal cervical os

Partial praevia, or grade III
– placenta is partially covering the internal cervical os

Complete praevia, or grade IV
– placenta is completely covering the internal cervical os

Question 5

What are some risk factors for placenta previa?

Answer 5

• Previous caesarean sections
• Previous placenta praevia
• Older maternal age
• Maternal smoking
• Structural uterine abnormalities (e.g. fibroids)
• Assisted reproduction (e.g. IVF)

Question 6

How does placenta previa usually present?

Answer 6

usually found on the 20-week anomaly scan

most women asymptomatic, can present with APH later in pregnancy around 36weeks

Question 7

How do you manage placenta previa if found at 20-weeks?

Answer 7

repeat vaginal scan at:
- 32 and then again at 36 weeks to guide delivery decisions

corticosteroids
- at 34 - 35+6 to mature fetal lungs

planned delivery between 36-37 weeks (incl low lying placenta)

Question 8

Main complication of placenta previa is haemorrhage before, during and after delivery… what urgent options do you have?

Answer 8

• Emergency caesarean section
• Blood transfusions
• Intrauterine balloon tamponade
• Uterine artery occlusion
• Emergency hysterectomy