Antenatal Care: Placenta Praevia & Plancetal Abruption Flashcards
What is placenta praevia?
Where the placenta is attached in the lower portion of the uterus, overlying the cervical os (lower than the presenting part of the fetus).
What is the most common a type of abnormal placental location?
Placenta praevia
Placenta praevia affects what % of pregnances?
0.5% - however incidence is rising.
What % of placenta praevia will resolve spontaneously?
Up to 90% of cases resolving spontaneously before becoming symptomatic - as the uterus grows and the placenta migrates upwards relative to the cervical os.
Risk of placenta praevia?
The condition is a major cause of maternal and fetal mortality and morbidity: cause of antepartum haemorrhage, vaginal bleeding in the 3rd trimester and indication for caesarean section
Definition of low lying placenta vs placenta praevia?
Low lying placenta: when the placenta is within 20mm of the internal cervical os
Placenta praevia: used only when the placenta is over the internal cervical os
What are the 3 causes of antepartum haemorrhage?
1) Placenta praevia
2) Placenta abruption
3) Vasa praevia
What are some causes of spotting or minor bleeding in pregnancy?
1) Cervical ectropion
2) Infection
3) Vaginal abrasions from intercourse or procedures.
Risks of placenta praevia?
1) Antepartum haemorrhage
2) Emergency C section
3) Emergency hysterectomy
4) Maternal anaemia and transfusions
5) Preterm birth and low birth weight
6) Stillbirth
What is the most important risk factor for placenta praevia?
Previous uterine scarring: typically the result of a C section (but other causes possible).
Risk factors for placenta praevia?
1) previous uterine scarring e.g. previous caesarean sections, previous placenta praevia
2) older maternal age
3) multiple pregnancies
4) large number of previous pregnancies
5) smoking
6) assisted reproduction (e.g. IVF)
7) structural uterine abnormalities (e.g. fibroids)
At what scan is the position of the placenta assessed in pregnancy?
20 week anomaly scan: assess the position of the placenta and diagnose placenta praevia.
Pathophysiology of placenta praevia?
1) Occurs when the blastocyst, which later develops into the placenta, implants into the lower uterine segment.
2) This can result in the placenta overlying the cervical os and obstructing the pathway of the fetus during labour.
Cause of bleeding in placenta praevia?
Number of reasons:
1) As the placenta is in a vulnerable location, bleeding can be triggered by pressure around the cervix causing minor placental trauma e.g. penetrative sex, vaginal exam
2) Labour & delivery:
- The placenta is at risk of rupture because it is blocking the path of the fetus
- This may results in massive haemorrhage from both the mother and fetus, leading to death
What is the classification of placenta praevia based on?
Based the relationship and distance between the placenta and the cervical os.
What are the 4 grades of placenta praevia?
Grade I: low lying placenta
Grade II: marginal praevia
Grade III: partial praevia
Grade IV: complete praevia
Describe grade I of placenta praevia
Low lying placenta:
a) The placenta is in the lower uterine segment but NOT reaching the internal cervical os
b) The lower edge of the placenta is 0.5-2cm from the internal cervical os
How far is the lower edge of the placenta from the internal cervical os in Grade I placenta praevia?
0.5 - 2cm
Describe grade II of placenta praevia
Marginal praevia:
a) The lower edge of the placenta reaches the internal cervical os
b) The placenta extents to the margin of the os but does not cover it
describe grade III of placenta praevia
Partial praevia: the placenta is partially covering the internal cervical os
Describe grade IV of placenta praevia
Complete praevia: the placenta completely covers the internal cervical os
How does the grade of placenta praevia affect prognosis?
Prognosis worsens with higher grades.
- Low lying placentas are found in 4-6% of pregnancies before 20 weeks, however up to 90% of these spontaneously resolve
- However, only 10% of complete praevias resolve.
What do all unresolved cases of complete praevia require?
Cesarean delivery
The RCOG guidelines (2018) recommend against using this grading system for placenta praevia now.
What 2 descriptions are more commonly used?
1) low-lying placenta
2) placenta praevia
Presentation of placenta praevia?
- Most asymptomatic
- Painless vaginal bleeding (antepartum haemorrhage): usually later in pregnancy (around or after 36 weeks)
How is placenta praevia often identified?
Placenta praevia is often identified before symptoms develop during a routine ultrasound appointment: anomaly scan.
When symptoms do present in placenta praevia, when do they typically occur?
3rd trimester
What is the main clinical feature of placenta parevia?
Painless vaginal bleeding: can range from spotting to life-threatening haemorrhage
Examination findings in placenta praevia?
- no evidence of a vaginal or cervical cause of the bleeding
- the uterus is not typically painful, unless in labour
What should be avoided in placenta praevia?
1) vaginal & rectal exams
2) intercourse
What investigation is used to diagnose placenta praevia?
Ultrasonography:
1) Transabdominal ultrasound detects placenta praevia in approximately 95% of cases
2) Transvaginal ultrasound detects the condition in almost 100% of patients.
What date is the routine anomaly scan?
Around 20 weeks
If placenta praevia/low lying uterus is found at anomaly scan, what is next step?
1) Follow-up transvaginal ultrasound at 32 weeks: to identify if case has resolved or not
2) If persisent: follow up subsequent transvaginal ultrasound to plan delivery at 36 weeks
If persistent placenta praevia is then identified at follw up transvaginal ultrasound at 32 weeks, what is next step?
Follow up at 36 weeks for a subsequent transvaginal ultrasound to plan delivery.
Depending on severity of bleeding in placenta praevia, what further investigations can be done?
1) FBC: maternal anaemia or platelet disorder
2) Clotting studdies: may aid in identifying bleeding disorders, but are only indicated if the platelet count is abnormal
3) Blood type and cross-match: required in preparation for surgery
4) The Kleihauer test: used in rhesus-negative mothers to determine the dose of anti-D required
5) Fetal cardiotocography (CTG): recommended for patients admitted to hospital to assess fetal wellbeing and aid in decision making
6) Biochemistry such as liver function tests and urea & electrolyte levels: can help rule out hypertensive disorders such as pre-eclampsia
Define antepartum haemorrhage
Bleeding after 28 weeks gestation
Give some differentials for placenta praevia
Other causes of antepartum haemorrhage and other placenta abnormalities:
1) Placental abruption
2) Miscarriage
3) Placenta accreta
4) Local causes of antepartum haemorrhage e.g. genital lesions (benign and malignant), genital lacerations and trauma, cervical ectropion and local infections.
Differentiating factors between placenta praevia and placental abruption:
a) pain
b) volume of bleeding
c) uterus on exam
d) US assessment
a)
placenta praevia: painless
placental abruption: painful
b) in both cases, volume of bleeding is incredibly variable
c) placental abruption: uterus more likely to be tense on examination
d) placental abruption: will show separation of the placenta from the uterine wall
Can placenta praevia and abruption co-exist in the same patient?
Yes
What is placental abruption?
Occurs when the placenta detaches from the endometrium and results in haemorrhage at the site of detachment.
Differentiating factors between placenta praevia and miscarriage:
a) bleeding
b) pain
c) when?
a)
miscarriage: sometimes accompanied by expulsion of products of conception
b)
placenta praevia: painless
miscarriage: often occurs alongside cramp-like abdominal pain
c)
placenta praevia: 3rd trimester
miscarriage: more common in 1st and 2nd trimesters
What examination signs of miscarriage may be present?
1) Cervical os may be open
2) Identification of products of conception
3) Uterine changes
Management of placenta praevia?
1) ABCDE if serious haemorrhage
2) Planned delivery with C section
3) Emergency caesarean section may be required with premature labour or antenatal bleeding.
4) Corticosteroids: where the gestational age is below 34 weeks
5) Tocolytics
6) Anti-D should be given with 72 hours of onset of bleeding in any resus negative mother
When should corticosteroids be given in placenta praevia?
Why?
Corticosteroids are given between 34 and 35 + 6 weeks gestation to mature the fetal lungs, given the risk of preterm delivery.
When is planned delivery considered in placenta praevia?
Planned delivery is considered between 36 and 37 weeks gestation.
It is planned early to reduce the risk of spontaneous labour and bleeding.
Purpose of given tocolytics in placenta praevia?
Tocolytics may be used to delay labour to provide maximum benefit from corticosteroids therapy
When should anti-D be given in any resus negative mother?
Anti-D should be given with 72 hours of onset of bleeding
Delivery in patients with minor placenta praevia (e.g. low lying placenta)?
Close monitoring - can deliver normally, however there is an increase risk of a requiring cesarean delivery.
What is the main complication of placenta praevia?
Haemorrhage: before, during and after delivery.
Management options of haemorrhage in placenta praevia?
1) Emergency caesarean section
2) Blood transfusions
3) Intrauterine balloon tamponade
4) Uterine artery occlusion
5) Emergency hysterectomy
Complications of placenta praevia?
1) Haemorrhage: risk increased by low pre-bleed maternal haemoglobin and iron stores.
2) Pre-term birth
3) Risks of c section
4) Foetal death
5) Intrauterine growth restriction
What is placenta abruption?
Refers to when the placenta separates from the wall of the uterus during pregnancy.
The site of attachment can bleed extensively after the placenta separates.
Placental abruption is a significant cause of antepartum haemorrhage.
What happens in placental abruption?
There is a compromise of the vascular structures supporting the placenta, which results in premature separation of the placenta from the normal lining of the uterus.
Onset of placenta praevia?
Often acute
Risk factors for placental abruption?
1) Chorioamnionitis: an infection of the placenta and the amniotic fluid
2) Alcohol ingestion
3) Pre-eclampsia
4) Overt HTN
5) Smoking
6) Advanced maternal age: happens more frequently in women >/= 35 BUT usually this has been attributed to multiparity (three or more deliveries) independent of age.
7) Cocaine use during pregnancy
8) Abdominal trauma: consider domestic violence
9) Previous placental abruption
How can chorioamnionitis lead to abruption of the placenta?
Bacterial colonisation at decidua may initiate inflammation of placental tissues and finally leads to the abruption of the placenta.
How can alcohol lead to abruption of the placenta?
It accumulates on the fetus and amniotic fluid after crossing the placenta. It causes vasospasm in the placenta and umbilical cord, which may lead to abruption.
How can pre-eclampsia lead to abruption of the placenta?
It is primarily a disease of the placenta and results in persistence of high resistance spiral arteries that impede placental perfusion.
This compromised placental perfusion leads to a decrease in blood flow to the developing foetus and results in complications such as placental abruption.
How can overt HTN lead to abruption of the placenta?
Causes potential changes in the vasculature of the placenta and leads to placental dysfunction.
How can smoking lead to abruption of the placenta?
Smoking and smoking by the partner are also an independent risk factor for abruption.
How can cocaine use lead to abruption of the placenta?
The high blood pressure and increased levels of catecholamines released by cocaine are considered to be responsible for the vasoconstriction in the uterine blood vessels that causes placental separation and abruption.
How can abdo trauma lead to abruption of the placenta?
Injuries cause separation of the placental attachment from decidua.
What to ask about in possible placental abruption history?
1) Previous pregnancies & problems (any placental abruption)
2) Smoking
3) Alcohol
4) Drug use (particularly cocaine or amphetamine)
5) Trauma: consider domestic violence
Presentation of placental abruption?
1) Sudden onset severe abdominal pain that is continuous
2) Vaginal bleeding (antepartum haemorrhage)
3) Shock (hypotension and tachycardia, faintness)
4) Abnormalities on the CTG indicating fetal distress
5) Characteristic “woody” abdomen on palpation, suggesting a large haemorrhage
6) May have back pain
What is the most common presentation of placental abruption?
Abnormal vaginal bleeding in the 2nd half of pregnancy.
N.B. In 20% of cases it is possible for the blood to become trapped inside the uterus (concealed), so even with a severe placental abruption, there might be no visible bleeding.
Describe the pain in placental abruption
1) Sudden onset abdo pain (over the uterus)
2) Continuous
How might the uterus feel on palpation in placental abruption?
Extremely hard and tender, and it does not relax.
‘Woody’ feel to the uterus on abdominal palpation indicates a significant placental abruption.
How can the severity of antepartum haemorrhage be defined?
1) Spotting: spots of blood noticed on underwear
2) Minor haemorrhage: less than 50ml blood loss
3) Major haemorrhage: 50 – 1000ml blood loss
4) Massive haemorrhage: more than 1000 ml blood loss, or signs of shock
How much blood is lost in a ‘minor’ haemorrhage?
Less than 50ml
How much blood is lost in a ‘major’ haemorrhage?
50-1000ml
How much blood is lost in a ‘massive’ haemorrhage?
> 1000ml or signs of shock
Investigations in placental abruption?
There’s no laboratory test or intervention to definitely diagnose placental abruption.
1) Abdo exam for signs of acute abdomen, or ‘woody’ feel to uterus
2) Supportive investigations should be performed to assess the extent and physiological consequences of vaginal bleeding.
3) In severe bleeding: full blood count and coagulation screen and 4 units of blood cross-matched.
4) U&Es
5) LFTs
6) Cardiotocograph to assess foetal heart (after stabilising mother)
7) Kleihauer-Betke test
8) US: can be used to diagnose placenta praevia but does not exclude abruption (can co-exist)
How can major haemorrhage associated with placental abruption affect the foetus?
1) Fetal hypoxia
2) May show repetitive late or variable decelerations, decreased beat‐to‐beat variability or bradycardia
What is a Kleihauer-Betke test?
Detects fetal blood cells in maternal circulation (does not diagnose the presence of placental abruption, but it quantifies the presence of fetal blood into the maternal circulation).
If significant fetal-maternal bleed is present, who can the Kleihauer-Betke test be useful?
The Kleihauer-Betke test results will help to determine the dose of anti-D immunoglobulin (anti-D Ig) to prevent isoimmunisation.
What is a concealed abruption?
Where the cervical os remains closed, and any bleeding that occurs remains within the uterine cavity.
Risk of concealed abruption?
The severity of bleeding can be significantly underestimated with concealed haemorrhage.
What is a revealed abruption?
where the blood loss is observed via the vagina.
Differentials for abnormal vaginal bleeding during the 2nd half of pregnancy?
Usually due to either placental abruption or placenta praevia.
It is important to differentiate these two conditions.
Onset of symptoms of placental abruption vs placenta praevia?
Placental abruption: onset is acute and severe
Placenta praevia: onset is quiet and insidious
Haemorrage in placental abruption vs placenta praevia?
Placental abruption: Haemorrhage may be visible or concealed
Placenta praevia: Haemorrhage is external and visible
Is abdo pain seen in placental abruption or placenta praevia?
Placental abruption
Foetal heart sounds in placental abruption vs placenta praevia?
Abruption: Fetal hearts sounds are absent or may show distress
Praevia: Normal
Differentials for placental abruption?
1) Placenta praevia
2) Chorioamnionitis
3) Pre term labour
4) Uterine fibroid degeneration
Management of placental abruption?
Obstetric emergency.
1) Initial resuscitation with fluid & oxygen
2) Monitoring of mother and fetus
3) May require delivery of baby (given corticosteroids)
4) Active monitoring of the 3rd stage: increased risk of postpartum haemorrhage after delivery in women with placental abruption
What does the urgency of placental abruption depend on?
The urgency depends on the amount of placental separation, extent of bleeding, haemodynamic stability of the mother and condition of the fetus.
What is it important to consider when assessing the severity of placental abruption?
Consider concealed haemorrhage, where the vaginal bleeding may be disproportionate to the uterine bleeding.
If a major or massive haemorrhage occurs in placenta praevia/placental abruption, what are the steps?
1) Urgent involvement of a senior obstetrician, midwife and anaesthetist
2) 2 x grey cannula
3) Bloods include FBC, UE, LFT and coagulation studies
4) Crossmatch 4 units of blood
5) Fluid and blood resuscitation as required
6) CTG monitoring of the fetus
7) Close monitoring of the mother
When would delivery of baby de considered in placental abruption?
Women with antepartum haemorrhage and associated maternal and/or fetal compromise are required to be delivered immediately.
What should be given to all the non-sensitised RhD negative cases of antepartum haemorrhage independent of whether routine antenatal prophylactic anti-D has been administered?
Anti-D immunogobulin
When are antenatal steroids offer?
offered between 24 and 34 + 6 weeks gestation to mature the fetal lungs in anticipation of preterm delivery.
Purpose of US in antepartum bleeding?
Ultrasound can be useful in excluding placenta praevia as a cause for antepartum haemorrhage, but is not very good at diagnosing or assessing abruption.
What do Rhesus-D negative women require when bleeding occurs?
anti-D prophylaxis
What test is done to determine the dose of anti-D given to rhesus-D negative women?
A Kleihauer test
Maternal complications of placental abruption?
1) Increased risk of placental abruptions in future pregnancies
2) Increased risk of postpartum haemorrhage.
3) Severe haemorrhage leads to hypovolemic shock
4) Hysterectomy to control bleeding from the uterus
5) Maternal death
6) Transfusion-associated complications
7) Coagulopathy
What operation can be done to control bleeding from uterus in major haemorrhage?
Hysterectomy
Foetal complications of placental abruption?
1) Premature birth
2) Stillbirth
3) Low birth weight
What is vasa praevia?
Where the fetal vessels are within the fetal membranes (chorioamniotic membranes) and travel across the internal cervical os i.e. the vessels are placed over internal cervical os, before the fetus.
The fetal membranes surround the amniotic cavity and developing fetus.
What do the fetal vessels consist of?
Two umbilical arteries and a single umbilical vein.
‘Praevia’ in latin?
Going before
Under normal circumstances, where does the umbilical cord containing the fetal vessels (umbilical arteries and vein) insert?
Inserts directly into the placenta.
There are two instances when the fetal vessels can be exposed, outside the protection of the umbilical cord or placenta.
What are they?
1) Velamentous umbilical cord: where the umbilical cord inserts into the chorioamniotic membranes, and the fetal vessels travel unprotected through the membranes before joining the placenta.
2) An accessory lobe of the placenta (also known as a succenturiate lobe): is connected by fetal vessels that travel through the chorioamniotic membranes between the placental lobes .
What is velamentous umbilical cord?
Where the umbilical cord inserts into the chorioamniotic membranes, and the fetal vessels travel unprotected through the membranes before joining the placenta.
what is an an accessory lobe of the placenta?
The accessory lobe is connected by fetal vessels that travel through the chorioamniotic membranes between the placental lobes.
Pathophysiology of vasa praevia?
1) fetal vessels are exposed, outside the protection of the umbilical cord or the placenta.
2) fetal vessels travel through the chorioamniotic membranes and pass across the internal cervical os (inner opening of the cervix)
3) these exposed vessels are prone to bleeding, particularly when the membranes are ruptured during labour and at birth.
4) can lead to dramatic fetal blood loss and death.
What are the 2 types of vasa praevia?
1) Type I vasa praevia – the fetal vessels are exposed as a velamentous umbilical cord
2) Type II vasa praevia – the fetal vessels are exposed as they travel to an accessory placental lobe
What type of vasa praevia involved the fetal vessels exposed as a velamentous umbilical cord?
Type I
What type of vasa praevia involved the fetal vessels exposed as they travel to an accessory placental lobe?
Type II
risk factors for vasa praevia?
1) Low lying placenta
2) IVF pregnancy
3) Multiple pregnancy
Presenation of vasa praevia?
Rupture of membranes followed immediately by vaginal bleeding.
Fetal bradycardia is classically seen
How is vasa praevia diagnosed?
1) US during pregnancy: ideal as it allows a planned caesarean section to reduce the risk of haemorrhag
2) May present with antepartum haemorrhage: with bleeding during the second or third trimester of pregnancy.
3) May be detected by vaginal exam during labour: when pulsating fetal vessels are seen in the membranes through the dilated cervix.
4) May be detected during labour: fetal distress and dark-red bleeding occur following rupture of the membranes
Is US reliable for diagnosing vasa praevia?
No - and it is often not possible to diagnose antenatally.
How may vasa praevia be detected by vaginal examination during labour?
When pulsating fetal vessels are seen in the membranes through the dilated cervix.
How may vasa praevia be detected during labour?
When fetal distress and dark-red bleeding occur following rupture of the membranes.
Risk of detecting vasa praevia during labour?
This carries a very high fetal mortality, even with emergency caesarean section.
Management of asymptomatic women with vasa praevia?
1) Corticosteroids: given from 32 weeks gestation to mature the fetal lungs
2) Elective caesarean section: planned for 34 – 36 weeks gestation
When is elective C section planned for in vasa praevia?
34-36 weeks gestation
Management of antepartum haemorrhage in vasa praevia?
Emergency C section.
After stillbirth or unexplained fetal compromise during delivery, the placenta is examined for evidence of vasa praevia as a possible cause.
What is placenta accreta?
When the placenta attaches deeper (to the myometrium), due to a defective decidua basalis.
As the placenta does not properly separate during labour there is a risk of postpartum haemorrhage.
What are the 2 major risk factors for placenta accreta?
1) Previous cesarean section: can cause defect in endometrium
2) Placenta praevia
What are the 3 layers to the uterine wall?
1) Endometrium (inner layer): contains connective tissue (stroma), epithelial cells and blood vessels
2) Myometrium (middle layer): contains smooth muscle
3) Perimetrium (outer layer): serous membrane similar to the peritoneum (also known as serosa)
What does the placenta usually attach to?
Endometrium: this allows the placenta to separate cleanly during the third stage of labour, after delivery of the baby.
Define superficial placenta accreta
Where the placenta implants in the surface of the myometrium, but not beyond
Define placenta increta
where the placenta attaches deeply into the myometrium
Define placenta percreta
where the placenta invades past the myometrium and perimetrium, potentially reaching other organs such as the bladder
Other risk factors for placenta accreta?
- Previous placenta accreta
- Previous endometrial curettage procedures (e.g. for miscarriage or abortion)
- Previous caesarean section
- Multigravida
- Increased maternal age
- Low-lying placenta or placenta praevia
There are 3 different types of placenta accreta, depending on the degree of invasion.
What are they?
1) Accreta: attach to myometrium
2) Increta: invade into the myometrium
3) Percreta: invade through perimetrium
Presentation of placenta accreta?
1) does not typically cause any symptoms during pregnancy
2) can present with bleeding (antepartum haemorrhage) in the 3rd trimester.
Diagnosis of placenta accreta?
1) can be diagnosed on antenatal ultrasound scans (particular attention is given to women with a previous placenta accreta or caesarean during scanning)
2) may be diagnosed at birth, when it becomes difficult to deliver the placenta.
It is a cause of significant postpartum haemorrhage.
Management of placenta accreta?
1) Ideally diagnosed by US to allow planning for birth
2) Additional management at birth due to the risk of bleeding and difficulty separating the placenta
3) Planned delivery between 35 to 36 + 6 weeks gestation: give corticosteroids
What investigation may be used to assess the depth and width of the invasion in placenta accreta?
MRI scan
What are options during cesarean in placenta accreta?
1) Hysterectomy with the placenta remaining in the uterus (recommended)
2) Uterus preserving surgery, with resection of part of the myometrium along with the placenta
3) Expectant management, leaving the placenta in place to be reabsorbed over time
Danger of expectant management in placenta accreta?
Expectant management comes with significant risks, particularly bleeding and infection.
Describe bleeding in placenta praevia
Painless & bright red
What is the strongest risk factor for placental abruption?
Having had a previous abruption.
Risk factors for placental abruption?
1) Blunt trauma e.g. car crash, fall, DV
2) Drugs: cocaine & methamphetamine (these cause vasoconstriction & increased BP)
3) Multiparity
4) Age >35
5) Previous abruption (strongest risk factor)
How can uterus feel in placenta abruption?
Tense - as muscle layer contracts to reduce uterine bleeding.
Complications of placental abruption?
Maternal:
- hypovolaemic shock
- Sheehan syndrome
- renal failure
- DIC
Foetal:
- intrauterine hypoxia & asphyxia
- premature birth
How can placental abruption cause DIC?
Large release of thromboplastin, which causes widespread clotting.
1st line imaging in placental abruption?
US
What will an US show in placental abruption?
Retroplacental collection of blood
