Antenatal - Placenta praevia, acreta, abruption and vasa praevia

Question 1

what is placenta praevia?

Answer 1

where the placenta is attached in the lower portion of the uterus, lower than the presenting part of the fetus

Question 2

define low-lying placenta and placenta praevia

Answer 2

low lying placenta = when placenta is within 20mm of the internal cervical os

placenta praevia is used only when the placenta is over the internal cervical os

Question 3

what are the 3 most important causes of antepartum haemorrhage?

Answer 3

placenta praevia

placental abruption

vasa praevia

Question 4

what are the risks/complications associated with placenta praevia?

Answer 4

• Antepartum haemorrhage
• Emergency caesarean section
• Emergency hysterectomy
• Maternal anaemia and transfusions
• Preterm birth and low birth weight
• Stillbirth

Question 5

what are the grades of placenta praevia? RCOG recommend against using this grading system as it is considered outdated

Answer 5

• Minor praevia, or grade I – the placenta is in the lower uterus but not reaching the internal cervical os
• Marginal praevia, or grade II – the placenta is reaching, but not covering, the internal cervical os
• Partial praevia, or grade III – the placenta is partially covering the internal cervical os
• Complete praevia, or grade IV – the placenta is completely covering the internal cervical os

Question 6

what are the risk factors for having placenta praevia?

Answer 6

• Previous caesarean sections
• Previous placenta praevia
• Older maternal age
• Maternal smoking
• Structural uterine abnormalities (e.g. fibroids)
• Assisted reproduction (e.g. IVF)

Question 7

when is the position of the placenta assessed?

Answer 7

20 week anomaly scan

Question 8

how may placenta praevia present?

Answer 8

painless vaginal bleeding - APH

usually occurs later in pregnancy, around/after 36 weeks

Question 9

how is placenta praevia managed?

Answer 9

in women who have bean diagnosed at 20 week anomaly scan it is recommended that they have a repeat transvaginal ultrasound scan at 32 weeks gestation and then at 36 weeks if present on the 32 week scan to guide delivery decisions

corticosteroids given between 34 and 35+6 weeks gestation to mature fetal lungs

planned delivery is considered between 36 and 37 weeks

planned early to reduce risk of spontaneous labour and bleeding - C section

depending on the position of the fetus and placenta different incisions may be made in the skin and uterus

may require ultrasound around time of procedure to locate placenta

Question 10

what is the major complication of placenta praevia and how is it managed?

Answer 10

haemorrhage before during or after delivery

manage with:

• emergency c section
• blood transfusions
• intrauterine balloon tamponade
• uterine artery occlusion
• emergency hysterectomy

Question 11

what is vasa praevia?

Answer 11

condition where the fetal vessels are within the fetal membranes and travel across the internal cervical os. normally the umbilical cord containing the fetal vessels inserts directly into the placenta so they are either protected by the cord or placenta at all times.

Question 12

what are the 2 occasions where the fetal vessels are exposed?

Answer 12

type 1 = velamentous umbilical cord where the cord inserts into the chorioamniotic membranes and the fetal vessels travel unprotected through the membranes before joining the placenta

type 2 = accessory lobe of the placenta is connected by fetal vessels that travel through the chorioamniotic membranes between placental lobes

Question 13

what are some risk factors for vasa praevia?

Answer 13

low lying placenta

IVF pregnancy

multiple pregnancy

Question 14

how might vasa praevia present?

Answer 14

may be diagnosed by ultrasound allowing for planned ceserean section due to risk of haemorrhage (not always possible to diagnose antenatally)

APH - bleeding in second or third trimester

may be seen on vaginally exam during labour with pulsating fetal vessels seen in the membranes through a dilated cervix

may be detected during labour when fetal distress and dark-red bleeding occur following rupture of the membranes - very high fetal mortality even with c section

Question 15

how is vasa praevia managed?

Answer 15

corticosteroids from 32 weeks gestation to mature fetal lungs

elective caesarean section planned for 34-36 weeks gestation

when APH - emergency section is requires to deliver fetus before death occurs

Question 16

what is placental abruption?

Answer 16

when the placenta separates from the wall of the uterus during pregnancy

Question 17

risk factors for placental abruption?

Answer 17

• Previous placental abruption
• Pre-eclampsia
• Bleeding early in pregnancy
• Trauma (consider domestic violence)
• Multiple pregnancy
• Fetal growth restriction
• Multigravida
• Increased maternal age
• Smoking
• Cocaine or amphetamine use

Question 18

how does placental abruption present?

Answer 18

• Sudden onset severe abdominal pain that is continuous
• Vaginal bleeding (antepartum haemorrhage) - may be no bleeding if it is concealed
• Shock (hypotension and tachycardia)
• Abnormalities on the CTG indicating fetal distress
• Characteristic “woody” abdomen on palpation, suggesting a large haemorrhage

Question 19

how does RCOG define severity of antepartum haemorrhage?

Answer 19

• 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 20

what is a concealed abruption?

Answer 20

where the cervical os remains closed and any bleeding that occurs remains within the uterine cavity. severity of bleeding can be significantly underestimated in concealed haemorrhage

(opposed to a revealed abruption where blood loss is observed via the vagina)

Question 21

how is placental abruption managed?

Answer 21

clinical diagnosis based on presentation

Emergency - urgency depends on amount of separation, extent of bleeding, haemodynamic stability of mother and condition of fetus

MUST CONSIDER CONCEALED HAEMORRHAGE

manage as major/massive haemorrhage

uss - excluding placenta praevia (not good for assessing abruption)

antenatal steroids betwen 24 and 34+6

rhesus D neg women require anti-D prophylaxis when bleeding occurs and kleihauer test to determine the dose of anti-D

emergency section

Question 22

initial steps with major or massive haemorrhage:

Answer 22

• 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

Question 23

what is there an increased risk of following placental abruption?

Answer 23

postpartum haemorrhage after delivery

active management of third stage is recommended

Question 24

what is placenta accreta?

Answer 24

when the placenta implants deeper through and past the endometrium into the myometrium and further, making it difficult to separate the placenta after delivery of the baby - referred to as placenta accreta spectrum as there is a spectrum of severity in how deep and broad the abnormal implantation extends

Question 25

what are some risk factors for developing placenta accreta?

Answer 25

• 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

Question 26

describe 3 classifications fo placenta accreta?

Answer 26

• Superficial placenta accreta is where the placenta implants in the surface of the myometrium, but not beyond
• Placenta increta is where the placenta attaches deeply into the myometrium
• Placenta percreta is where the placenta invades past the myometrium and perimetrium, potentially reaching other organs such as the bladder

Question 27

how does placenta accreta present?

Answer 27

doesn’t usually cause any symptoms during pregnancy - can present as APH in 3rd trimester

may be diagnosed on antenatal ultrasound scans - particular attention given to women with previous placenta accreta or Caesarean

may be diagnosed at birth when it becomes difficult to deliver - significant cause of postpartum haemorrhage

Question 28

how is placenta accreta managed?

Answer 28

ideally dx by antenatal uss - allows planning for birth

MRI scan can be used to assess depth and width of invasion

MDT approach as require additional management at birth due to risk of bleeding and difficulty separating the placenta (complex uterine surgery, blood transfusions, ITU)

delivery is planned between 35 to 36+6 to reduce risk of spontaneous labour and delivery

Question 29

what options are there during c section for the management of placenta accreta?

Answer 29

• Hysterectomy with the placenta remaining in the uterus (recommended)
• Uterus preserving surgery, with resection of part of the myometrium along with the placenta
• Expectant management, leaving the placenta in place to be reabsorbed over time

Question 30

RCOG guidelines on placenta accreta

Answer 30

if placenta accreta is seen when opening the abdomen for an elective caesarean section, the abdomen can be closed and delivery delayed whilst specialist services are put in place. If placenta accreta is discovered after delivery of the baby, a hysterectomy is recommended.