Placental development / Pathology Flashcards
What is vasa praevia
Vasa praevia occurs when exposed fetal vessels within the amniotic membranes cover or are in close proximity to the internal cervical os.
What are the 2 types of vasa praevia
Type 1 vasa praevia occurs with velementous insertion of the umbilical cord into the placenta
Type II vasa praevia occurs with a velamentous fetal vessel connecting the placenta to a succinuriate placental lobe
What is the incidence?
1:2500 pregnancies
What is the affect of antenatal diagnosis?
What is the perinatal mortality
with antenatal dx
without antenatal dx?
Diagnosing vasa praevia prenatally is associated with a significant reduction in perinatal mortality and morbidity
Dx 97% survival
No dx 44% survival
What limits prenatal dx?
Limited by: Abdominal wall scarring Obesity Empty bladder Direct of the fetal vessels
What causes false positives?
Not uncommon
Motion artifacts
Umbilical cord presentation
Marginal placental sinus
How is it diagnosed?
Transvaginal ultrasound using colour and pulse-wave Doppler to evaluate the internal os and lower uterine segment is the most accurate means to diagnose vasa praevia.
Diagnostic criteria for vasa praevia?
Visualising aberrant linear or tubular echolucent structures with 2D imaging
Demonstrating blood flow in these structures using colour or power Doppler
Demonstrating umbilical arterial/venous Doppler waveforms using pulse wave Doppler
Aberrant vessels located over or within 2cm of the internal os attached to the inner perimeter of the fetal membranes
Should vasa praevia be screened for with TV USS?
Why not?
Uncommon
No evidence that universal screening of the general population would be accurate, practical or improve perinatal outcomes
Not cost effective
What is the association between velamentous cord insertion and vasa praevia? When? What do we look for? How accurate is it? What signs encourage further Ix?
Where possible, universal screening at the routine mid-trimester scan to locate the placental cord insertion using transabdominal ultrasound and colour Doppler is recommended
Occurance of vasa praevia in the absence of a velamentous cord insertion is negligable
Screening TA USS for velamentous cord insertion or the presence of a multilobed placenta has been proposed
Velamentous insertion occurs in 1% pregnancies
Vasa praevia occurs in 2% of velamentous cord insertions
Accuracy for 20 weeks USS for velamentous insertions: Sensitivity 62% PPV 100% NPV 99.5%
What increases your risk of a vasa praevia ?
What are the biggest risk factors?
Bilobed placenta OR 22 Succinturate lobes OR 22 Praevia Hx low lying placenta in T2 OR 22 IVF (increases risk to 1:200) Multiple pregnancy
So what do we use for targeted screening?
Targeted screening
TA T2 USS for placental location, and CI
If the placenta is more then 2 cm from the internal ox no further Ix is needed
If the placenta is within 2 cm, succenturiate or bilobed, velamentous cord insertion, IVF or multiple pregnancy then TA scan of the Cx with colour doppler
If there are suspicious findings or poor visualisation then a TVs can is performed to optimize the diagnosis
How to managed a patient with vasa praevia and no bleeding:
Admission to hospital from 30 weeks gestation until the time of delivery to expedite urgent emergency delivery in the event of membrane rupture, vaginal bleeding or preterm labour;
Administration of corticosteroids for fetal lung maturation in anticipation of preterm delivery;
Admission and delivery in a hospital with paediatric expertise and appropriate level of neonatal care;
Delivery by elective caesarean section prior to the onset of labour. consider del by 35 weeks
Are there any other approaches to managing the stable non bleeding patient other then admission?
Other options include:
Outpatient management of select asymptomatic singleton cases with a long closed cervix on serial transvaginal ultrasound scans and a negative fetal fibronectin - This option is supported by a retrospective cohort study published in 2013 which reported a 4% risk of preterm emergency delivery in singleton pregnancies diagnosed prenatally.
The optimal gestation at which to admit patients with a prenatal diagnosis of vasa praevia may depend on the circumstances of the patient and availability of the appropriate inpatient facilities.
Transvaginal ultrasound with colour Doppler to map fetal vessels preoperatively to avoid iatrogenic laceration and intraoperative fetal haemorrhage
Emergency management
for vasa praevia
When to suspect?
What is the emergency management?
Vasa praevia should be suspected in pregnancies with fresh vaginal bleeding (+/- membrane rupture) and acute fetal compromise with heart rate abnormalities such as progressive tachycardia, prolonged bradycardia or sinusoidal pattern.
In the presence of bleeding from suspected vasa praevia, delivery by urgent Caesarean section is appropriate with paediatric support for neonatal resuscitation including possible immediate transfusion with O Rh negative blood. Those responsible for care of the neonate should be advised of the suspected fetal blood loss prior to caesarean section.
What is a placenta accreta?
increta?
percreta?
Accreta: Morbid adherence of the placenta to the uterine wall
Increta: Deep invasion into the myometriumn
Percreta: invasion through the uterus to the serosa +/- to surrounding structures
How to manage a pregnancy with accreta antenatally?
Encouraged to remain close to the planned hospital of confinement for T3
Deliver earlier gestation then uncomplicated ELLSCS / praevias due to the desire to avoid acute delivery
How to diagnose an accreta?
TV USS dx
MRI does not demonstrate superiority over TVUSS
Difficult dx – if there is a suspicion, management should be planned on the assumption that placetna accreta is present.
How to prepare for delivery?
Who is involved?
What is required?
Optimisation of maternal haemaglobin + iron stores
Patient consented and prepared for blood transfusion and hysterectomy
Surgical team should be ready for rapid escalation
Appropriate expertise
Obstetric, neonatal, anaesthetic, haematological, ICU
MDT approach with possible prior consultation with urology, gynae onc, vascular, interventional radiologists
MTP that everyone is familiar with with the ability to give high volume blood transfusions, and avaliability of other blood products
Cell saver
What are the surgical approach options for accreta?
- Delivery of the baby and attempted delivery of the placenta. This is associated with a high likelihood of hysterectomy.
- Delivery of the baby via a uterine incision distant from the placenta, quick repair of the uterus and en bloc hysterectomy.
- Delivery of the baby via a uterine incision distant from the placenta, trimming of the cord close to insertion site, full repair of the uterus and conservative management.
2/3 avoid hysterectomy
1/3 still need a hysterectomy
because of uncontrollable bleeding, which may be delayed up to several weeks, and this approach also has a significant risk of infectious morbidity.
Reasonably good future fertility rates and pregnancy outcomes but with an increased rate of recurrent placenta accreta 17-29%
Can consider ureteric stenting – especially if a percreta
Interventional radiology can have a role
The role of placement of balloon catheters prior to delivery in placenta accreta requires further evaluation
