Obstetrics: Antenatal Care- Placenta Complications Flashcards
Define antepartum haemorrhage
State some possible causes of PV bleeding in 1st, 2nd and 3rd trimester
Bleeding after 24 weeks gestation
State some causes of antepartum haemorrhage
- Placenta praevia
- Vasa praevia
- Placental abruption
- Benign or malignant lesions – e.g. polyps, carcinoma. cervical ectropion (common)
- Infections – e.g. candida, bacterial vaginosis and chlamydia.
Should vaginal examination be performed in antepartum haemorrhage?
*vaginal examination should not be performed in primary care for suspected antepartum haemorrhage - women with placenta praevia may haemorrhage
How does RCOG define severity of antepartum haemorrhage?
*HINT: there are 4 categories
- 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 placenta praevia?
How common in placenta praevia?
- Placenta praevia is where the placenta is fully or partially attached to the lower uterine segment
- 1% pregnancies
RCOG recommend using the descriptions ‘low-lying placenta’ and ‘placenta praevia’; however, traditionally there are 4 grades of placenta praevia- describe these
- Minor praevia/grade I = the placenta is in the lower uterus but not reaching the internal cervical os
- Marginal praevia/grade II = the placenta is reaching, but not covering, the internal cervical os
- Partial praevia/grade III = the placenta is partially covering the internal cervical os
- Complete praevia/grade IV = the placenta is completely covering the internal cervical os
****The RCOG guidelines (2018) recommend against using this grading system, as it is considered outdated.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
What is a low-lying placenta?
Placenta is within 20mm of internal cervical os
State some risk factors for placenta praevia
- Previous caesarean sections (embryo more likely to implant in scar)
- Previous placenta praevia
- Multiparity
- Multiple pregnancy
- Older maternal age (>35/40yrs)
- Maternal smoking
- Structural uterine abnormalities (e.g. fibroids)
- Assisted reproduction (e.g. IVF)
Describe how placenta praevia may present
- Many are asymptomatic and it is detected on 20-week anomaly scan
- May present with painless vaginal bleeding in pregnancy (antepartum haemorrhage)- usually occurs later in pregnancy ~36 weeks or after
Discuss the management of placenta praevia and low-lying placenta
If have low-lying placenta or placenta praevia diagnosed in early pregnancy (e.g. 20 week anomaly scan):
- Repeat transvaginal ultrasound at 32 weeks gestation and again at 36 weeks gestation if still present on 32 week scan
If still have low-lying placenta or placenta praevia later in pregnancy:
- Corticosteroids between 34 and 35+6 weeks to mature fetal lungs given the risk of preterm delivery
- Planned caesarean section between 36 and 37 weeks gestation
- Ultrasound performed at time of delivery to check position of placenta and fetus as different incisions may have to be made
- If woman has premature labour or antenatal bleeding then may have to do emergency caesarean section (PassMed says if goes into premature labour must do C-section to prevent post-partum haemorrhage)
Why is delivery planned early (between 36 and 37 weeks) in placenta praevia?
To reduce risk of spontaneous delivery & bleeding
State some potential complications of placenta praevia
- Haemorrhage (before, during and after delivery)
Main complication of placenta praevia is haemorrhage. Discuss potential management options of haemorrhage
A-E assessment and:
- Emergency caesarean section
- Blood transfusions
- Intrauterine balloon tamponade
- Uterine artery occlusion
- Emergency hysterectomy
Notes from Teachmeobygyn about antepartum haemorrhage questions
The following questions are useful to ask in the assessment of antepartum haemorrhage:
- How much bleeding was there and when did is start?
- Was it fresh red or old brown blood, or was it mixed with mucus?
- Could the waters have broken (membranes ruptured?)
- Was it provoked (post-coital) or not?
- Is there any abdominal pain?
- Are the fetal movements normal?
- Are there any risk factors for abruption? e.g. smoking/drug use/trauma – domestic violence is an important cause.
If the bleed is ongoing, or if there has been a significant vaginal bleed, ABC assessment and resuscitation is vital. If the woman is clinically stable, proceed to examination.
General Examination
On general examination, the following should be assessed:
- Pallor, distress, check capillary refill, are peripheries cool?
- Is the abdomen tender?
- Does the uterus feel ‘woody’ or ‘tense’ (which may indicate placental abruption)?
- Are there palpable contractions?
- Check the lie and presentation of the fetus/fetuses. Ultrasound can be used to help.
- Check fetal wellbeing with a cardiotocograph (CTG) at 26 weeks gestation or above: (otherwise auscultate the fetal heart only).
- Read the hand-held pregnancy notes: are there scan reports? This will be helpful in establishing whether there could be placenta praevia
Assessment of Bleeding
Lastly, the bleeding itself should be assessed:
- Externally e.g. by looking at pads.
-
Cusco speculum examination: avoid this until placenta praevia has been excluded by USS.
- Look for whether blood is fresh red or dark. How much blood is there? Are there clots? Are there any cervical lesions? Is there any cervical dilatation, or any chance that the membranes have ruptured?
- Take triple genital swabs to exclude infection if the bleeding is minimal
-
Digital vaginal examination: A digital vaginal examination with known placenta praevia should NOT be performed as it could cause massive bleeding.
- In minor bleed, when placenta praevia is excluded, it can help to establish whether the cervix is beginning to dilate.
- Avoid digital VE if the membranes have ruptured.
What is vasa praevia?
Condition in which fetal vessels (umbilical arteries & vein) are within the fetal membranes (chorioamniotic membranes)- hence are unprotected- and travel across internal cervical os
Discuss the pathophysiology of vasa praevia- include the two types
- Normally, umbilical cord inserts directly into placenta and hence fetal vessels are always protected by either umbilical cord or the placenta
- There are two types of vasa praevia:
- Type I: fetal vessels are exposed as a velamentous umbilical cord (umbilical cord inserts into chorioamniotic membrane and then fetal vessels travel unprotected through membranes before joining the placenta)
- Type II: fetal vessels are exposed as they travel to an accessory placental lobe (accessory lobe is connected to placental lobes by fetal vessels which travel through chorioamniotic membrane)
Remind yourself of the 3 layers of the uterine wall
- Endometrium: inner layer that contains connective tissue (stroma), epithelial cells and blood vessels
- Myometrium: middle layer that contains smooth muscle
- Perimetrium: outer layer, which is a serous membrane similar to the peritoneum (also known as serosa)
When talking about placenta accreta we use different definitions to describe the depth of invasion; define the following:
- Superficial placenta accreta
- Placenta increta
- Placenta percreta
- Superficial placenta accreta: the placenta implants in the surface of the myometrium, but not beyond
- Placenta increta: the placenta attaches deeply into the myometrium
- Placenta percreta: the placenta invades past the myometrium and perimetrium, potentially reaching other organs such as the bladder
What is placental abruption?
Part or all of placenta separates from wall of uterus during pregnancy; site of attachment can bleed extensively after placenta separates hence it is a cause of antepartum haemorrhage
