Antenatal - Placenta praevia, acreta, abruption and vasa praevia Flashcards
what is placenta praevia?
where the placenta is attached in the lower portion of the uterus, lower than the presenting part of the fetus
define low-lying placenta and placenta praevia
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
what are the 3 most important causes of antepartum haemorrhage?
placenta praevia
placental abruption
vasa praevia
what are the risks/complications associated with placenta praevia?
- Antepartum haemorrhage
- Emergency caesarean section
- Emergency hysterectomy
- Maternal anaemia and transfusions
- Preterm birth and low birth weight
- Stillbirth
what are the grades of placenta praevia? RCOG recommend against using this grading system as it is considered outdated
- 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
what are the risk factors for having placenta praevia?
- Previous caesarean sections
- Previous placenta praevia
- Older maternal age
- Maternal smoking
- Structural uterine abnormalities (e.g. fibroids)
- Assisted reproduction (e.g. IVF)
when is the position of the placenta assessed?
20 week anomaly scan
how may placenta praevia present?
painless vaginal bleeding - APH
usually occurs later in pregnancy, around/after 36 weeks
how is placenta praevia managed?
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
what is the major complication of placenta praevia and how is it managed?
haemorrhage before during or after delivery
manage with:
- emergency c section
- blood transfusions
- intrauterine balloon tamponade
- uterine artery occlusion
- emergency hysterectomy
what is vasa praevia?
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.
what are the 2 occasions where the fetal vessels are exposed?
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
what are some risk factors for vasa praevia?
low lying placenta
IVF pregnancy
multiple pregnancy
how might vasa praevia present?
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
how is vasa praevia managed?
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
what is placental abruption?
when the placenta separates from the wall of the uterus during pregnancy
risk factors for placental abruption?
- 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
how does placental abruption present?
- 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
how does RCOG define severity of antepartum haemorrhage?
- 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
what is a concealed abruption?
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)
how is placental abruption managed?
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
initial steps with major or massive haemorrhage:
- 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
what is there an increased risk of following placental abruption?
postpartum haemorrhage after delivery
active management of third stage is recommended
what is placenta accreta?
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
what are some risk factors for developing 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
describe 3 classifications fo placenta accreta?
- 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
how does placenta accreta present?
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
how is placenta accreta managed?
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
what options are there during c section for the management of placenta accreta?
- 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
RCOG guidelines on placenta accreta
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.
