Bleeding: Placental Abruption & Praevia; Vasa praevia)

Question 1

Define what is meant by placental abruption [1]

Answer 1

Placental 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.

Question 2

TOM TIP: The three causes of antepartum haemorrhage to remember are [3]

Answer 2

TOM TIP: The three causes of antepartum haemorrhage to remember are placenta praevia, placental abruption and vasa praevia.

These are serious causes with high morbidity and mortality. Causes of spotting or minor bleeding in pregnancy include cervical ectropion, infection and vaginal abrasions from intercourse or procedures.

Question 3

The RCOG guideline (2011) defines the severity of antepartum haemorrhage as:

Spotting: [1]
Minor haemorrhage:[1]
Major haemorrhage: [1]
Massive haemorrhage: [1]

Answer 3

The RCOG guideline (2011) defines the severity of antepartum haemorrhage as:

Spotting:
- spots of blood noticed on underwear

Minor haemorrhage:
- less than 50ml blood loss

Major haemorrhage:
- 50 – 1000ml blood loss

Massive haemorrhage:
- more than 1000 ml blood loss, or signs of shock

Question 4

The typical presentation of placental abruption is with: [6]

Answer 4

• Sudden onset severe abdominal pain that is continuous
• Uterine contractions may cause additional pain
• Vaginal bleeding (antepartum haemorrhage) - DURING 2ND HALF OF PREGNANCY. Painful, dark-red, non-clotting and usually non recurrent vaginal bleeding
• Shock (hypotension and tachycardia)
• Abnormalities on the CTG indicating fetal distress
• Characteristic “woody” abdomen on palpation, suggesting a large haemorrhage

NB: The amount of vaginal bleeding can vary greatly, and doesn’t necessarily indicate how much of the placenta has separated from the uterus.

Question 5

Name some key risk factors for placental abruption [+]

Answer 5

• Previous abruption (8-10x) * Cocaine / amphetamines
• Cigarette smoking (2x)
• HTN (3x)/ PET(2x)
• Fetal growth restriction
• Bleeding in the first trimester (1.5x)
• Thrombophilia
• Advanced maternal age
• Multiparity
• Low BMI
• IVF
• Intrauterine infection * PPROM
• Multiple pregnancy
• Trauma
• Rapid uterine decompression

Answer 6

Concealed abruption is where the cervical os remains closed, and any bleeding that occurs remains within the uterine cavity.

The severity of bleeding can be significantly underestimated with concealed haemorrhage.

NB: Concealed abruption is opposed to revealed abruption, where the blood loss is observed via the vagina.

Question 7

Describe the difference between revealed and concealed placental abruptions

Answer 7

Question 8

Describe how you manage placental abruption

Answer 8

Placental abruption is an obstetric emergency:
* Urgent involvement of a senior obstetrician, midwife and anaesthetist
* 2 x grey cannula
* Bloods include FBC, UE, LFT and coagulation studies
* Crossmatch 4 units of blood
* Fluid and blood resuscitation as required
* CTG monitoring of the fetus
* Close monitoring of the mother
* Active management of stage 3 labour
* Corticosteroids for baby between 24th and 34th weeks of getation

NB: It is important to consider concealed haemorrhage, where the vaginal bleeding may be disproportionate to the uterine bleeding.

Question 9

How do you decide whether to deliver baby if has placental abruption? [4]

Answer 9

Women with antepartum haemorrhage and associated maternal and/or fetal compromise are required to be delivered immediately.

While RCOG does not recommend premature delivery of fetus in women with less than 37 weeks of gestation with no fetal and maternal compromise.

If gestational age is equal to or more than 37 weeks and the bleeding presents as spotting or mucus streaks of blood, active intervention is unlikely needed.

Minor or major antepartum bleeding, RCOG suggests inducing labour with the aim of achieving vaginal delivery to avoid serious complications related to placental abruption

Question 10

Abnormal vaginal bleeding during the second half of pregnancy is usually due to either [2].

It is important to differentiate these two conditions.

Answer 10

Placental abruption:
- placenta partially or completely detaches itself from the uterine wall before delivery.
- Haemorrhage may be visible or concealed
- abdominal pain are intense and acute
- Fetal hearts sounds are absent or may show distress

placenta praevia:
- the placenta is located over or near the cervix, in the lower part of the uterus
- haemorrhage external and visible with placenta praevia
- less abdominal pain
- fetal heart sounds normal

Question 11

Define placental praevia [1]

Answer 11

Definition: Abnormal implantation of the placenta in the lower uterine segment with different grades of encroachment on the cervix.

Question 12

What is the most likely cause of placental praevia? [1]

Answer 12

previous uterine scarring:
- typically from c-section
- scarring leads to placenta implanting into the lower uterine segment
- this causes decreased vascularisation in the top, so implants below

Question 13

Describe the pathophysiology of placenta praevia [+]

Answer 13

• abnormal trophoblastic invasion of the endometrium. Normally, implantation occurs within the upper uterine segment, where a rich blood supply supports fetal development.
• Instead, as gestation progresses and lower uterine segment elongates and thins during third trimester - leads to: vascular disruption can cause bleeding as maternal vessels are torn away from the anchoring points; ineffective haemostasis; cervical effacement and dilatation
• Anatomically, placenta praevia impedes normal labour progression by obstructing the birth canal

Question 14

What are the 4 classifications of placenta praevia [4]

Answer 14

Grade 1
- also known as a low lying placenta
- The placenta is in the lower uterine segment
- The lower edge of the placenta is 0.5-2cm from the internal cervical os

Grade 2
- also known as marginal praevia
- The lower edge of the placenta reaches the internal cervical os
- The placenta extents to the margin of the os but does not cover it

Grade 3
- also known as partial praevia
- The placenta partially covers the internal cervical os

Grade 4
- also known as complete praevia
- The placenta completely covers the internal cervical os

NB: The RCOG guidelines (2018) recommend against using this grading system, as it is considered outdated. The two descriptions used are low-lying placenta and placenta praevia.

Question 15

What are the clinical features of placenta praevia? [+]

Answer 15

Often identified before symptoms develop during a routine ultrasound appointment.

Main symptoms:
- Painless vaginal bleeding from 30+ weeks
- uterus is not typically painful, unless in labour

Question 16

What is the definitive dx of placenta praevia? [1]

Answer 16

ultrasonography at 20 week routine anamoly scan

Question 17

What is the difference in timelines with regards to placenta praevia c.f miscarriage? [1]

Answer 17

Miscarriage is more common in the 1st and 2nd trimesters - placenta praevia often causes symptoms in the 3rd trimester

Question 18

How do you manage placenta praevia?

Answer 18

Diagnosed early in pregnancy (e.g. at the 20-week anomaly scan):
- Repeat scan at 32. If still present..
- Repeat at 36 weeks gestation

Corticosteroids are given between 34 and 35 + 6 weeks gestation to mature the fetal lungs, given the risk of preterm delivery.

Planned delivery is considered between 36 and 37 weeks gestation. It is planned early to reduce the risk of spontaneous labour and bleeding
- Planned cesarean section is required with placenta praevia and low-lying placenta (< 20mm from the internal os).

Question 19

What advice do you give to patients who have placental abruption during the pregnancy [3]

Answer 19

Recommend pelvic rest:
* No penetrative intercourse
* No vaginal douching
* Avoid vaginal examination unless completely necessary

Question 20

Describe the differences between placental praevia and abruption between the following:

• Bleeding
• Painful
• Abdominal pain
• General conditions
• Height and feel of uterus
• DIC
• Fetal distress

Answer 20

Question 21

Define vasa praevia [1]

What are the two types? [2]

Answer 21

Fetal vessels coursing through the membranes over the internal cervical orifice and below the fetal presenting part, unprotected by placental tissue or the umbilical cord.
- The fetal vessels consist of the two umbilical arteries and single umbilical vein.

Type 1 (A): Velamentous cord insertion in single or bilobed placenta.

Type 2 (B): Fetal vessels running between accessory lobes.

NB: Vasa translates from Latin as vessel. Praevia translates from Latin as “going before”. Vasa praevia is where the vessels are placed over internal cervical os, before the fetus.

Question 22

Describe the pathophysiology of vasa praevia (describe normal vs abnormal formations)

Answer 22

Normally:
- umbilical cord containing the fetal vessels (umbilical arteries and vein) inserts directly into the central portion of the placenta.
- The fetal vessels are always protected, either by the umbilical cord or by the placenta.
- The umbilical cord contains Wharton’s jelly. Wharton’s jelly is a layer of soft connective tissue that surrounds the blood vessels in the umbilical cord, offering protection.

Vasa praevia:
- Eccentric or marginal insertion of the umbilical cord. Get either:
- Velamentous cord insertion: umbilical cord inserts into the chorioamniotic membranes rather than centrally into the placental mass. The blood vessels branch out from this point and travel within these membranes before reaching their connection with the placenta. OR
- Bilobed or succenturiate-lobed placentas: variations in placental morphology where there’s more than one lobe to a placenta. If a blood vessel connects two lobes across fetal membranes that traverse overlying cervical os, it can lead to vasa praevia.

Question 23

Further subclassification of vasa praevia can be made based on clinical presentation:

What are they? [2]

Answer 23

Ramified Vasa Praevia:
- Also known as branching vasa praevia, it involves multiple small-calibre vessels crossing over the internal os.

Funic Presentation Vasa Praevia:
- Characterised by a single large vessel running over or near the internal os, often associated with a funic presentation of umbilical cord.

Question 24

Describe the clinical features of vasa praevia [5]

Answer 24

Painless PV Bleeding:
- Most common
- Often sudden and can be heavy

Abnormal Fetal Heart Rate Patterns:
- Due to compromise in fetal blood supply
- Most commonly bradycardia

Rupture of membranes:
- The membrane rupture exposes the unprotected vessels causing them to tear and bleed.

Fetal Anemia
- In cases where there has been chronic slow leakage from the vasa praevia, fetal anemia may occur due to gradual loss of fetal blood.

Fetal Distress or Death:
- If not promptly diagnosed and managed, vasa praevia can lead to severe fetal distress due to hypoxemia and even intrauterine death.

Question 25

Describe the management of suspect vasa praevia [3] and emergency vasa praevia [2]

Answer 25

Suspected vasa praevia: hospital admission between 28-32w, antenatal steroids, elective CS between 35-37w

Undiagnosed vasa praevia: emergency cat 1 CS and aggressive fetal resuscitation

Question 26

How do you differentiate vasa praevia from premature rupture of membranes? [1]

Answer 26

While both conditions can lead to membrane rupture, vasa praevia is associated with blood-stained amniotic fluid and significant changes in fetal heart rate patterns following rupture.

In contrast, PROM typically presents with clear amniotic fluid and does not directly cause changes in fetal heart rate unless it leads to complications such as cord prolapse or chorioamnionitis.