[40] Placenta Praevia Flashcards
What is placenta praevia?
Where the placenta is fully or partially attached to the lower uterine segment
Why is placenta praevia clinically important?
Because it is an important cause of antepartum haemorrhage
What are the main types of placenta praevia?
- Minor
- Major
What is minor placenta praevia?
Placenta is low, but does not cover the internal cervical os
What is major placenta praevia?
Placenta lies over the internal cervical os
What is the problem with placenta praevia?
A low lying placenta is more susceptible to haemorrhage
Why is a low lying placenta more susceptible to haemorrhage?
Possibly due to defective attachment to the uterine wall
What can cause the bleeding in placenta praevia?
- Spontaneous
- Provoked by mild trauma, e.g. vaginal examination
- Damage as presenting part of the fetus moves into the lower uterine segment in preparation for labour
What is the main risk factor for placenta praevia?
Previous C-section
What is the incidence of placenta praevia with 1 previous C-section?
1 in 160
What is the incidence if placenta praevia with 2 previous C-sections?
1 in 60
What is the incidence of placenta praevia with 4 previous C-sections?
1 in 10
What are the other risk factors for placenta praevia?
- High parity
- Maternal age >40 years
- Multiple pregnancy
- Previous placenta praevia
- History of uterine infection (endometritis)
- Curettage of endometrium after miscarriage or termination
How might placenta praevia be detected if asymptomatic?
May be incidental finding on routine anomaly ultrasound
How does placenta praevia classically present?
Painless vaginal bleeding
How severe is the vaginal bleeding in placenta praevia?
Varies from spotting to massive haemorrhage
When might there be pain in placenta praevia?
If the woman is in labour
What might examination reveal in placenta praevia?
Risk factors pertinent to placenta praevia, e.g. c-section scar or multiple pregnancy
Is the uterus tender on palpation in placenta praevia?
Not usually
What are the differentials for placenta praevia?
- Placental abruption
- Vasa praevia
- Uterine rupture
- Local genital causes
What is vasa praevia?
Where fetal blood vessels run near the internal cervical os
What is vasa praevia characterised by?
Triad of;
- Vaginal bleeding
- Rupture of membranes
- Fetal compromise
When does the bleeding occur in vasa praevia?
Following the rupture of membranes
Why does the bleeding occur following the rupture of membranes in vasa praevia?
Because there is rupture of umbilical cord vessels
What does the rupture of umbilical cord vessels in vasa praevia lead to?
A loss of fetal blood and rapid deterioration in fetal condition
What local genital causes are differentials for placenta praevia?
- Benign or malignant lesions
- Infections
What benign or malignant lesions can be differentials for placenta praevia?
- Polyps
- Carcinoma
- Cervical ectropion
What infections can be differentials for placenta praevia?
- Candida
- BV
- Chlamydia
What should be done regarding investigations if major bleeding is suspected?
Perform investigations and resuscitate simultaneously
What investigations should be done in placenta praevia?
- Bloods
- Assess fetal wellbeing
- Imaging
What bloods should be done in placenta praevia?
- FBC
- Clotting profile
- Kleihauer test
- G&S
- Crossmatch
- U&Es and LFTs
Why should FBC be done in placenta praevia?
To asses for any maternal anaemia
When should Kleihauer test be done in placenta praevia?
If the woman is rhesus negative
What does the Kleihauer test determine?
The amount of feto-maternal haemorrhage
Why is it important to determine the amount of feto-maternal haemorrhage in rhesus negative women?
To determine the dose of anti-D required
When is crossmatch required in placenta praevia?
If clinical presentation is likely to warrant transfusion
Why are U7Es and LFTs done in suspected placenta praevia?
To exclude pre-eclampsia and HELLP syndrome, and any other organ dysfunction
How should an assessment of fetal wellbeing be made in women above 26 weeks?
CTG
How is the definitive diagnosis of placenta praevia made?
Ultrasound
What will be shown on ultrasound in placenta praevia?
Short distance between lower edge of placenta and internal os
How is minor placenta praevia managed?
Repeat scan at 36 weeks is recommended
Why is a repeat scan at 36 weeks recommended in minor placenta praevia?
As the placenta is likely to have moved
What repeat scanning is recommended in major placenta praevia?
Repeat at 32 weeks
Why is the scan repeated at 32 weeks in major placenta praevia?
As a plan for delivery is made at this time
What is required for delivery in placenta praevia?
C-section
What should women with major placenta praevia be advised not to do?
Have penetrative sexual intercourse
What decision has to made in women with major placenta praevia?
About location of care after 34 weeks gestation
Who can potentially receive outpatient care with major placenta praevia?
Women who remain asymptomatic, i.e. no bleeding
What do women with major placenta praevia who are considering outpatient care require to make their decision?
Careful counselling
What are the requirements for outpatient care for major placenta praevia after 36 weeks?
- Close proximity to the hospital
- Constant companion
- Fully informed consent of the woman
When should a woman receiving home-based care for major placenta praevia be advised to visit the hospital immediately?
If she experiences any bleeding, contractions, or pain
Which patients with major placenta praevia should be encouraged to stay in hospital from 34 weeks gestation?
Women who have experienced a bleed
When should C-section be performed for placenta praevia?
Where possible, should be deferred to 38 weeks
Why should the C-section be deferred to 38 weeks in placenta praevia?
To minimise neonatal morbidity
What should be considered when planning the timing of elective C-section in placenta praevia?
The benefits of additional maturity should be weighed against the risk of major haemorrhage and the possibility that repeated small haemorrhage can cause IUGR
What is placenta accreta?
Morbidly adherent placenta
Who has a high risk of placenta accreta?
Women with placenta praevia who have previously had a C-section
When should placenta accreta be considered as a possible diagnosis?
In any situation where any part of the placenta lies under the previous C-section scar, even if not praevia
How can a definitive diagnosis of placenta accreta be made?
Only at surgery
How should a C-section be performed if there is suspicion of placenta accreta?
The uterus should be opened at a site distant to the placenta, and the baby should be born without disturbing the placenta
Why should a C-section be performed without disturbing the placenta in placenta accreta
Because it allows either conservative management of the placenta, or hysterectomy if accreta is confirmed
What should you not do when there is acute bleeding associated with placenta praevia?
Perform a vaginal examination
Why should you not perform a vaginal examination when there is acute bleeding associated with placenta praevia?
As this may start torrential bleeding
What needs to be considered regarding blood loss in acute bleeding caused by placenta praevia?
Should assess blood loss and cross-match for possible transfusion
What is indicated in acute bleeding caused by placenta praevia?
Resuscitation
Who is the priority when resuscitating because of acute blood loss caused by placenta praevia?
The mother
What should be done as a result of the mother being the priority in resuscitation for acute blood loss caused by placenta praevia?
The mother should be stabilised before any assessment of the fetus
What surgical intervention may be required in acute bleeding caused by placenta praevia?
In severe bleeding, the baby is delivered urgently, whatever its gestational age
Hysterectomy may be required in severe cases
What should be done if the patient is bleeding due to placenta praevia, but immediate delivery is not likely?
Maternal steroids may be indicated
Why might maternal steroids be indicated when bleeding due to placenta praevia but immediate delivery not likely?
To promote fetal lung development and reduce the risk of respiratory distress syndrome and IV haemorrhage
What are the potential complications of placenta praevia?
- Potentially fatal hypovolaemic shock
- Fetal haemorrhage, prematurity, intrauterine asphyxia, or birth injury
