Placenta praevia

Question 1

Risk factors?

Answer 1

Previous CS 
Any uterine surgery; incl repeat D&C
ART
Smoking
Twins and multiple birth
Uterine malformation

Question 2

Screening of p praevia?

Answer 2

Anatomy scan at 20/40 identifies women at risk

Should have a repeat USS at 32/40
If perisistant praevia/LLP then repeat again at 36/40 to discuss MOD

TVUSS superior to TA and safe

Consider measuring cervical length before 34/40 in women with praevia- shortened cervix and praevia = more likely to go into labour early and have massive haemorrhage at CS

Question 3

Definition of placenta praevia (AIUM)

Answer 3

> 16/40
Placenta lying directly over the internal os- praevia
Placenta lying within 20mm of internal os- low lying placenta
Placenta >20mm from internal os = normal (someone should tell Waitakere Hospital…)

Question 4

Management of LLP/praevia at home versus hospital

Answer 4

Take into account:

• asymptomatic vs episodes of bleeding
• Timing of first bleed (<29/40 highest risk)
• Social circumstances
• Access to transport/emergency services
• acceptance of receiving blood products

If managed at home- ensure they have access to transport, safety precautions in place, help and know TCI if any vaginal bleeding/pain etc

Question 5

Use of steroids

Answer 5

Between 34+0 and 35+6/40, prior to 34/40 if at risk of preterm birth

Question 6

Timing of delivery

Answer 6

If bleeding/or other risk factors for preterm birth- aim for 34+0-36/40

If asymptomatic aim for 36+0-37+0 (RCOG)

Question 7

Vaginal delivery and LLP

Answer 7

Can be considered based on woman’s risk factors, obstetric hx, location of placental edge in relation to fetal head

Question 8

Steps to optimise delivery

Answer 8

Access to blood products and have available (consider cell salvage if JW or particular risk for haemorrhage)
Discussion in advance re acceptance of blood products
Discussion re hysterectomy/risk of major obstetric haemorrhage
Large bore IV access x2
X-match blood
Optimise Hb antenatally
Senior staff (e.g. SMO obs/anaesthetic) should be immediately available e.g. in OT or performing procedure

Question 9

Surgical approach to delivery

Answer 9

Consider vertical skin/uterine incisions when fetus transverse lie, particularly before 28/40
Consider pre-op/intra-op USS to identify exact location of placenta and optimal location for uterine incision
If placenta transected during uterine incision immediately clamp umbilical cord to minimise fetal blood loss
Manage PPH with ecbolics, early use of surgical techniques/tamponade and consider early embolisation.
Early recourse to hysterectomy if needed

Question 10

Incidence of placenta praevia

Answer 10

1:200 pregnancies

Risk increases with number of CS and with previous multiple births

Question 11

% of placenta praevia/LLP that has resolved by term?

Answer 11

90%

Although figure lower for women who have had a previous CS

Question 12

Risks of bleeding according to gestation

Answer 12

4.7% by 35 weeks of gestation,
15% by 36 weeks of gestation,
30% by 37 weeks of gestation
59% by 38 weeks of gestation

Question 13

RANZCOG:

a. List six risk factors for placenta previa. (3 marks)

Answer 13

• Multiparity
• Previous CS
• Smoking
• ART
• Multiple pregnancy
• Previous uterine surgery e.g. D+C

Question 14

RANZCOG:

A 25 year old woman, at 20 weeks gestation in her second pregnancy, has a low-lying placenta on her routine morphology scan. You are seeing her to discuss this finding in a rural location and she wants to know her likelihood of having a placenta previa in the third trimester. She has not had any bleeding during this pregnancy.

b. What information at this point is useful to predict the likelihood that her placenta will remain low lying in the third trimester? Discuss three prognostic features in detail. (8 marks)

Answer 14

1. Anterior vs posterior – posterior placenta is more likely to remain low lying – anterior lower uterine segment grows more in third trimester
2. Previous CS – less likely to migrate. Also risk factor for accreta/increta/percreta - if the placenta is pathologically adherent to, or invasive of, the myometrium it is highly likely to remain that way
3. Whether covering the os completely or just low – significant migration unlikely if placenta substantially overlaps the so by >25mm

Question 15

RANZCOG:

At 36 weeks gestation, her anterior placenta is found to cover the internal os on ultrasound scan. She has no antepartum haemorrhage and there is no evidence of placenta accreta.

c. List at least eight aspects of this delivery you will consider to optimise the outcome. (4 marks)

Answer 15

Pre-operative
• Planned elective procedure in tertiary centre with MDT involvement - obstetric, anaesthetics, blood bank, NICU, midwifery +/- interventional radiology
• Good quality images to determine likelihood of placenta accreta
• Optimise Hb
• Consider elective admission particularly as she is in a rural location
• Plan pre-labour CS – consider delivery during 38th week to minimize the risk of spontaneous labour (RCOG states 36-37/40)
• Discussion and planning re: blood products – and plans in place if blood products declined, e.g. cell-saver, iron infusion
• Pre-operative discussion and consent include possibility of hysterectomy or interventional radiology if uncontrolled blood loss, and leaving placenta in situ if accreta. Discuss implications for future fertility.

Intra-operatively
• Valid G&S and X-matched blood available, consider cell saver
• Senior obstetrician
• Avoid incision of placenta if possible
• Anticipate PPH – active management of third stage and swiftly secure haemostasis
• Quick recourse to hysterectomy if excessive bleeding

Question 16

Incidence of placenta praevia?

Answer 16

1:200