Placental Abnormalities and Complications Flashcards
What is the placenta accreta spectrum?
Range of pathologic adherence of the placenta (accreta, increta, percreta)
What does placenta accreta spectrum include?
Accreta, increta, percreta
What is placenta accreta?
abnormal invasion of the placental villi through the decidua leading to adherence to the myometrium.
What is placenta increta?
abnormal invasion of the placental villi through the decidua and into the myometrium, through to the outer serosa.
What is placenta percreta?
abnormal invasion of the placental villi through the entire uterine wall; it may then invade other organs.
What causes defective endometrial-myometrial interface in placenta percreta?
Scarring
What does defective endometrial-myometrial interface in placenta percreta cause?
Defective endometrial-myometrial interface causes failure of normal decidualisation - this allows the placental villi (trophoblast) to invade further
What leads to massive obstetric haemorrhage in placenta percreta?
Failure to detect and manage placenta accreta
Common risk factor for placenta percreta?
Previous caesarean section
Name 2 other risk factors for placenta percreta?
Other uterine surgery + Increased maternal age
Presentation of placenta percreta
Typically detected in antenatal period: ○ Women with previous CS found to have low-lying placenta are specifically screened with ultrasound scanning
What is the management for placenta percreta?
Caesarean section at 35-37 weeks (This may be uterus-preserving if the accreta is limited and placenta can be safely
separated.
○ Otherwise, RCOG guidelines recommend caesarean section hysterectomy with
placenta left in situ in the uterus.
)
When is the caesarean section performed?
35-37 weeks
What does RCOG recommend if placenta cannot be separated?
Hysterectomy
What is placenta praevia?
Placenta covers internal os of the cervix
What defines a low-lying placenta?
Within 20 mm of internal os (placenta lies within 20 mm of the internal os (but does not cover it)
What is aetiology of placenta praevia?
Blastocyst implants in the lower segmentof the uterus
Causes of bleeding due to placental trauma?
Placental Trauma (or spontaneous) : sexual intercourse, vaginal examination, cervical dilation in labour
What are risk factors for bleeding due to placental trauma?
Previous C-section, IVF, previous placenta praevia
When is antepartum haemorrhage diagnosed?
> 24 weeks
If bleeding < 24 weeks - what do you suspect?
Threatened miscarriage
What is the presentation of antepartum haemorrhage?
Painless bleeding, soft, non-tender uterus
When is bleeding usually diagnosed without symptoms?
20 week anatomy scan
When is a follow up scan indicated for if praevia/ low lying?
At 32 weeks
When is a follow up scan indicated for if not resolved?
36 weeks
What is used to diagnose antepartum haemorrage when symptomatic?
Transvaginal ultrasound
Investigation of antepartum haemorrhage steps?
- Full blood count, group + save
- Kleihauer test
- Transvaginal / transabdominal ultrasound 4. CTG for foetal monitoring
Kleihauer test is for?
Fetomaternal haemorrhage in Rhesus -ve women
Differentials for antepartum haemorrhage?
Placental abruption, onset of labour, cervical ectropion, vasa praevia
Management for placenta praevia antenatally?
Conservative follow-up, oral corticosteroids (Conservative management with follow up scanning as described above. PP often spontaneously resolves as the uterus grows and lower pole
stretches in later pregnancy.
○ Single course of oral corticosteroids is indicated between 34 and 36 weeks.)
Management for placenta praevia via delivery?
Placenta praevia: Aim to deliver by caesarean section at 36-37 weeks for uncomplicated placenta praevia. ■ High risk of massive obstetric haemorrhage (12x background risk). ○ Low-lying placenta: trial of labour is offered, particularly if 10-20mm from os; caesarean section is also offered.
When is delivery by caesarean section recommended for uncomplicated placenta praevia?
36-37 weeks
What is the risk associated with massive obstetric haemorrhage?
12x background risk
What is offered for low-lying placenta?
Trial of labour or caesarean (particularly if 10-20mm from os;
caesarean section is also offered)
What is Placenta Praevia?
The placenta overlies the cervical os. It can present with OR without bleeding, and may be completely asymptomatic.
→ Bright red vaginal bleeding during pregnancy
Risk Factors for Placenta Praevia
● Multiparity and multiple pregnancies
● Previous C-Section
● Uterine scarring and abnormalities
● Previous placenta praevia (increases risk to 4-8% of subsequent pregnancies)
● Advanced maternal age
Ix for Placenta Praevia
● Typically, placenta praevia is detected around 20 weeks during a routine anomaly scan.
If low-lying placenta at the 20-week scan do another scan at:
● 32 weeks gestation
If placenta praevia detected then scan at:
● 36 weeks gestation (to guide decisions about delivery)
● elective caesarean section for grades III/IV between 37-38 weeks
● if grade I then a trial of vaginal delivery may be offered
Management of Placenta Praevia
Placenta praevia with bleeding:
● admit!
● ABC approach to stabilise the woman
● if not able to stabilise → emergency caesarean section
Placenta praevia with no bleeding and not in labour:
● Monitor with ultrasound scans
● Aim for caesarean at 37-38 weeks
What is placental abruption?
Premature separation of the placenta from the decidua
What causes the placental abruption?
Chronic processes & acute trigger
What are chronic processes involved in placental abruption?
Placental thrombosis & infection
What does chronic processes like placental thrombosis and infection lead to?
Hypoperfusion & infarction, and shallow trophoblast invasion
What predisposes the placenta to premature separation ?
Chronic processes such as placental thrombosis and infection cause hypoperfusion, placental infarction, and shallow trophoblast invasion.
What happens after the placenta is predisposed to separation?
This is followed by a non-specific acute trigger (mechanical force within the abdomen) which causes the poorly adherent placenta to separate from underlying decidua.
What does separation of the placenta from the decidua cause?
Maternal decidual vessels rupture
What accumulates between placenta and decidua?
Blood
What does normal placental separation depend on?
Placental contraction (- In normal placental separation, bleeding is stemmed by placental contraction; this
is not possible when the foetus is in situ and the myometrium is stretched.)
What does decidual bleeding cause?
Excess thrombin production (due to tissue factor AKA clotting factor 3-mediated activation of the extrinsic clotting pathway). This leads to enhanced matrix metalloproteinase expression and endothelial injury, alongside release of proinflammatory cytokines.
What effects does thrombin have?
Uterotonic effects - this would explain uterine contraction and rupture of membraines in response to abruption
High levels of systemic thrombin can lead to?
consumptive coagulopathy i.e. disseminated intravascular coagulation.
Strongest risk factor for abruption?
Previous abruption
Name 3 other risk factors for abruption?
Pre-eclampsia, trauma, smoking, cocaine
Types of abruption?
Concealed, Revealed, Mixed
What is concealed placental abruption?
- blood remains behind the placenta, preventing a PV bleed
What is revealed placental abruption?
blood escapes from behind the placenta, causing a PV bleed.
What is mixed placental abruption?
- clot forms behind placenta alongside PV bleed.
Presentation of abruption?
Antepartum haemorrhage , abdominal pain, woody hard, contracilte uterus
Is ultrasound reliable for diagnosis placental abruption?
No
How is the placental abruption diagnosed?
Clinically
What is the first line management of placental abruption?
Category 1 caesarean section
Placental Abruption
● Placenta separates from the wall of the uterus during pregnancy
● Site of attachment can bleed extensively after placenta separates
● Oxygen supply to foetus is compromised and maternal blood loss may be significant
Risk Factors for Placental Abruption
● Previous placental abruption
● Pre-eclampsia
● Bleeding early in pregnancy
● Trauma (consider domestic violence)
● Multiple pregnancy
● Foetal growth restriction
● Multigravida
● Increased maternal age
● Smoking
● Cocaine or amphetamine use
Ix for Placental Abruption
● A tense, tender uterus with a ‘woody’ feel
● Ultrasound is not reliable
● Heart rate abnormalities on CTG
● Platelet count
● Coagulation screen
→ Depending on the degree of detachment and the amount of blood loss, the mother may collapse, the foetus can become hypoxic and potentially die.
Management of Placental Abruption
● First line: Emergency CS
- Increased risk of PPH
● Urgency depends on
- Amount of placental separation
- Extent of bleeding
- Haemodynamic stability
- Condition of foetus
● Ultrasound
- Exclude placenta praevia
● Antenatal steroids- dexamethasone
- Between 24 and 34+6 weeks
● Anti-D prophylaxis for rhesus negative women
Management of Placental Abruption if Fetus is alive and < 36 weeks (fetal distress/ no distress)
fetal distress: immediate caesarean
no fetal distress: observe closely, steroids, no tocolysis, threshold to deliver depends on gestation
What is Vasa Praevia?
Malformation of foetal vessels (umbilical vein + arteries), leading them to run through placental membranes instead of the umbilical cord.
What happens to exposed foetal vessels in Vasa Praevia during labour?
Rupture and haemorrhage (Exposed foetal vessels are liable to rupture and haemorrhage in labour due to cervical
dilatation or movement of the presenting part, particularly if they overlie the cervical os)
Risk of vasa praevia in pregnancies?
uncommon, estimated between 1 in 1200 to 1 in 5000 pregnancies
Mortality rate if undiagnosed vasa praevia and SROM occurs?
Foetal mortality is 60%
Presentation of vasa praevia before birth?
Antepartum haemorrhage ; resulting in antenatal dx
Presentation of vasa praevia during labour?
Vaginal bleeding after SROM at onset of labout with foetal distress
What scan is used in antenatal detection of vasa praevia?
Transvaginal ultrasound
What Ix is used for vasa praevia during labour?
Vaginal examinations (palpable foetal vessels overlying os)
What is given at 32 weeks for high risk of prematurity post antenatal detection?
Corticosteroids
What is the recommended timing for elective CS?
34-36 weeks, although optimal timing is contested
If the vasa praevia were undetected, what is the management?
Category 1 caesarean section
What is the classification of vasa praevia?
split into either type 1 or type 2
What classification of vasa praevia type involves foetal vessels connected to velamentous umbilical cord)?
Type 1
What is the type 2 classfication of vasa praevia?
Foetal vessel connected to succenturiate** placental lobe
What is the velamentous cord?
cord inserted into foetal membranes, not placenta
What is the succenturiate lobe?
accessory lobe connected to the main body of the placenta
