Placenta accreta spectrum

Question 1

Risk factors for accreta

Answer 1

• Previous history of accreta
• Previous caesarean delivery/ other uterine surgery. Risk increases as the number of prior CS increases.
• AMA
• ART

Previous caesarean delivery and the presence of an anterior low-lying placenta or placenta praevia should alert the antenatal care team of the higher risk of placenta accreta spectrum and women should be specifically screened for accreta

Question 2

Accuracy of USS for diagnosing accreta?

Answer 2

Highly accurate when TV scan performed by a skilled operator with experience in diagnosing placenta accreta spectrum

Should be scanned in a unit with scanning expertise

Under these circumstances it is comparable to MRI

Question 3

Management of accreta

Answer 3

Antenatal diagnosis crucial

Optimise Hb antenatally

Consent:

• General caesarean section risks
• Specific risks: massive obstetric haemorrhage, lower urinary tract damage, blood transfusion, hysterectomy

Discuss blood products and consider cell salvage and interventional radiology

Delivery- most senior team available

Question 4

Role of MRI in accreta

Answer 4

The diagnostic value of MRI and ultrasound imaging is similar when performed by experts.

MRI can complement ultrasound by assessing:

1. Depth of invasion
2. Lateral extension of myometrial invasion, especially with posterior placentation and/or in women with ultrasound signs suggesting parametrial invasion.

Question 5

Timing of delivery

Answer 5

If no risk factors for preterm delivery aim for 35+0 to 36+6

A contingency plan for emergency delivery should be developed

Delivery in a centre with facilities for complex surgery and peripartum hysterectomy

Question 6

Consenting for CS for accreta

Answer 6

Massive obstetric haemorrhage, 
increased risk of lower urinary tract damage, 
blood transfusion 
hysterectomy.
Talk about cell salvage and IR

Question 7

Surgical approach to CS

Answer 7

• Skilled operator
  3 options:
  1. Delivery of the baby and attempted delivery of the placenta. High likelihood of hysterectomy and bleeding.

2. Delivery of the baby via a uterine incision distant from the placenta, quick repair of the uterus and en bloc hysterectomy.
3. Delivery of the baby via a uterine incision distant from the placenta, repair the uterus and conservative management.
   - Preferable to perform hysterectomy and leave placenta in situ
   - Can consider ureteric stents. Not evidence based.

Question 8

Uterus conserving approach to management of accreta

What are the risks?

Answer 8

-Leave placenta in situ and close uterus

• Post op care: regular review, ultrasound examination
• Women need access to emergency care in case of complications such as bleeding or infection
• No evidence for methotrexate

Risks: secondary hysterectomy (30%), infection, bleeding, mortality (3.7%), in up to 70% of women (small study) they were able to conceive again

Question 9

Definition of accreta spectrum

Answer 9

Spectrum- ranges from morbidly adherent to deeply invasive placenta

Accreta: where the villi adheres superficially to the myometrium without interposing decidua;

Increta: where the villi penetrate deeply into the uterine myometrium down to the serosa

Percreta: the villous tissue perforates through the entire uterine wall and may invade the surrounding pelvic organs, such as the bladder

Question 10

Incidence of accreta

Answer 10

Between 1:300 and 1:2000

Question 11

USS features of placenta accreta

2D greyscale signs:

Answer 11

Loss of the ‘clear zone’ (i.e. abscence of decidua basalis)
Abnormal placental lacunae 
Placental bulge 
Myometrial thinning 
Bladder wall interruption
Focal exophytic mass

Doppler: hypervascularity and turbulent blood flow extending from placenta into surrounding tissues

Question 12

MRI features of placenta accreta

Answer 12

• Uterine bulging,
• intraplacental bands,
• Heterogeneous placenta,
• Disorganised vasculature of placenta
• Focal interruptions of the endometrial myometrial border

Question 13

Surgical management for percreta

Answer 13

1. Primary hysterectomy following delivery of the fetus, without attempting placental separation.
2. Delivery of the fetus avoiding the placenta, with repair of the incision leaving the placenta in situ
3. Delivery of the fetus without disturbing the placenta, followed by partial excision of the uterine wall (placental implantation site) and repair of the uterus.
4. Delivery of the fetus without disturbing the placenta, and leaving it in situ, followed by elective secondary
   hysterectomy 3–7 days following the primary procedure

No evidence to strongly support each method. Conservative approach not recommended due to very high (nearly 60% risk) of requiring secondary hysterectomy, and significant infectious morbidity.

Also consider cystoscopy and ureteric stents prior to surgery if suspicion of bladder invasion

Question 14

Risk of accreta spectrum with a known LLP/praevia by increasing number of CS?

Answer 14

CS increases the risk of placenta accreta spectrum 7 fold

0 CS = 3.3 - 4%
>/= 3 CS = 50 - 67%

Question 15

Risk of uterus conserving management

Answer 15

Risks:

secondary hysterectomy (30%),
infection,
bleeding,
mortality (3.7%),