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
Risk factors for acceta?
Prev hx of accreta
Prev LSCS
risk of accreta increases 7X after 1 prev LSCS
More caesareans, the higher the risk
Prev uterine surgery including repeat endometrial currette, MROP, myomectomy, post partum endometritis
OR for accreta after previous uterine surgery is 3.4
Also increased risk is anatomic uterine abnormality eg bicornuate uterus, adeomyosis, submucous fibroids, myotonic dystrophy
Short CS to conception interval
increased maternal age
ART
AMA - 35 or more
3% of praevia is accreta (deficient endometrium in lower segment) if no previous LSCS
50-70% if 3 or more LSCS
Who should we discuss the risk of accretas with?
RCOG
Women requesting elective caesarean delivery for non‐medical indications should be informed of the risk of placenta accreta spectrum and its consequences for subsequent pregnancies
Risk factors for abruption (18)
Previous abruption - 4.4% incidence of recurrent abruption 2 prev abruptions recurrence 25% PET FGR non vertex presentation Polyhydramnios AMA Multiparity Low BMI ART Intrauterine infection Prenatal rupture of membranes Abdominal trauma Smoking Drug use – cocaine and amphetamines First trimester bleeding (increased 1% to 1.4%) Intrauterine haematoma – increases the risk abruption 5.6X Maternal thombophilias - Heterozygous factor V leiden, heterozygous prothrombin 2021-A
how common is APH in pregnancy ?
How does it contribute to global mortality
APH is bleeding from or into the genital tract occurring from 24 weeks
3-5% pregnancies
20% very preterm babies are associated with APH (explains associated with preterm delivery)
Obstetric hemorrhage world wide is associated with 50% mortalities
praevia risk factors
rates of increased risk iwth prev LSCS
Previous praevia OR 9.7 Previous caesarean general 2.2 1 prev LSCS2.2 2 prev LSCS 4.1 3 prev LSCS 22.4 Prev TOP Multip Multiple pregnancy AMA over 40 Smoking Deficient endometrium due to presence of Uterine scar Endometritis Manual removal of placenta Curettage Submucosa fibroid Assisted conception
** consider domestic violence
What does not help praevia management / what do we avoid?
Avoid vaginal and rectal exams
Advise woman to avoid penetrative sexual intercourse
Cervical cerclage is not supported by evidence
No role in prophylactic tocolytics for praevia to prevent bleeding
Maternal complications of APH
Anaemia Infection Maternal shock Renal tubular necrosis Consumptive coagulopathy PPH Prolonged hospital stay Psychological sequelae Complications of blood transfusion Maternal mortality
Fetal complications of APH
Fetal hypoxia
SGA and FGR
Prematurity
Fetal death
What increases the likelihood of complications with an APH?
Heavy bleeding
placental in origin
earlier gestation
What Ix for APH
Investigations
Need to assess the extent and physiological consequence of the bleeding
Kleihauer is not a sensitive test to diagnose abruption
It must be done in Rh neg woman to quantify the amount of anti D to give
Abruption is a clinical diagnosis
Bloods
If major or massive obstetric haemorrhage – FBC, coags, 4U X match urea, electrolytes, LFTs
Minor do FBC and G+H – if low platelets then do a coag
USS
Placental location
Poor sensitivity for dx of retroplacental clot
Sensitivity 24%
Fetal Ix
CTG once resuscitation has commenced
Monitor CTG if it will influence delivery
USS if no FHB auscultated
The British association for perinatal medicine states if the fetus is pre viable then continuous monitoring not advised
Evidence is lacking for point of care testing to differentiate fetal from materal blood
Steroids and tocolysis wit hAPH
Steroids
Clinicians should offer a single course of antenatal corticosteroids to women between 24+0 and 34+6 weeks of gestation at risk of preterm birth.
In women presenting with spotting, where the most likely cause is lower genital tract bleeding, where imminent delivery is unlikely, corticosteroids are unlikely to be of benefit, but could still be considered.
Tocolytics
Should not be used to delay delivery in a woman presenting with major APH, unstable or there is fetal compromise
A Snr obstetrician should make any decision regarding tocolysis
Benefits are very preterm, requiring hospital transfer, not steroid complete
If use nifedipine is probably best avoided as it is associated with maternal hypotension
What intrapartum monitoring? massive APH Major APH Minor APH Spotting a few weeks ago
Monitoring in labour
Women in labour with active vaginal bleeding require continuous electronic fetal monitoring.
In women who are in preterm labour whose pregnancies have been complicated by major APH or recurrent minor APH, or if there has been any clinical suspicion of an abruption, then continuous electronic fetal monitoring should be recommended.
In women who have experienced one episode of minor APH, in which there have been no subsequent concerns regarding maternal or fetal wellbeing, intermittent auscultation is appropriate.
Women with minor APH with evidence of placental insufficiency (such as fetal growth restriction or oligohydramnios) should be recommended to undergo continuous electronic fetal monitoring
How to manage third stage?
Postpartum haemorrhage (PPH) should be anticipated in women who have experienced APH.
Women with APH resulting from placental abruption or placenta praevia should be strongly recommended to receive active management of the third stage of labour.
Consideration should be given to the use of ergometrine-oxytocin (Syntometrine® [Alliance, Chippenham, Wilts]) to manage the third stage of labour in women with APH resulting from placental abruption or placenta praevia in the absence of hypertension (see Green-top Guideline No.52)
How to manage anti D for recurrent APHs
Anti-D Ig should be given to all non-sensitised RhD-negative women after any presentation with APH, independent of whether routine antenatal prophylactic anti-D has been administered.
In the non-sensitised RhD-negative woman in the event of recurrent vaginal bleeding after 20+0 weeks of gestation, anti-D Ig should be given at a minimum of 6-weekly intervals.
In the non-sensitised RhD-negative woman for all events after 20+0 weeks of gestation, at least 500 iu anti-D Ig should be given followed by a test to identify FMH greater than 4 ml red blood cells; additional anti-D Ig should be given as required.
What blood products should be offered?
What to give in a massive APH while waiting for the bloods?
In women who have experienced a massive blood loss or a major abruption, the development of a disseminated intravascular coagulation (DIC) should be considered. Clotting studies and a platelet count should be urgently requested and advice from a haematologist sought. Up to 4 units of FFP and 10 units of cryoprecipitate may be given whilst awaiting the results of the coagulation studies
Post natal care
Post natal care
Thrombophophylaxis Debriefing 4-6 weeks post natally Contract numbers for support Clinical incident reporting
What is the incidence of praevia?
Incidence of accreta?
praevia 1/200
accreta 1/300 - 1/2500 (depending on definitions)
Risk factors for praevia
Prev LSCS 1 prev RR 4.5 2 prev 7.4 3 prev 6.5 4 prev 45
Risk 1 prev LSCS 1% to 2.8% with 3+ prev LSCS
Short time from LSCS to conception increases risk RR 1.7
EL LSCS - increases risk praevia next pregnancy OR 2.6
Smoking OR 1.42
ART - RR 3.7 for praevia - confirmed on metaanalysis
Contradicting reports about twins and praevia
AMA may have a slight increase in risk but may be parity related
Do we screen for praevia?
How many move from the anatomy scan?
When to rescan?
how to rescan
RCOG
Midpregnancy scan include pregnancy localisation
Terms praevia or low lying can be used after 16 weeks
FU USS at 32 weeks then again at 36 weeks to plan delivery
Exact timing depends on extent based on perceived risk - if prev LSCS earlier to R/o accreta
at 32 weeks 90% of placentas will have moved
after 32 weeks 50% of placentas move
no further changes after 36 weeks
TV USS is beneficial if posterior placenta, obscured view due to fibroids, or obesity
It is safe
TVS at anatomy will reclassify 25-60% low lying as normal
RCOG GL
What is the role in cervical length measurement in woman with praevia
CL is a predictor of APH and EMLSCS preterm for woman with praevia
a CL less then 31 mm identifies woman with a higher risk of LSCS before 34 weeks and 16X more likely to have a EMLSCS due to massive haemorrhage
Placental edge more then 10mm and Cx less then 30 for massive haemorrhage
Woman with cx length less then 25 have a RR of 7.2 for massive haemorrhage at LSCS
Serial cx length may have a role for assessing risk of haemorrhage
Where is it best to manage woman with praevia?
In or outpatient
What factors may you use to make a decision
Decision make case by case IP vs OP management
Factors
Womans needs
social factors - distance from hospital, availability of transport, previous bleeding episodes, Hb, acceptable of donor blood,
Risks below increase chance of emergency delivery and massive haemorrhage
Gestation of first bleed (increased risk if before 29 weeks) Number of APH 1 prev APH risk of EM delivery OR 7.5 2 - OR 14 3 OR 27
Prev LSCS
APH requiring blood transfusion
Can use this to decide who gets steroids and when, who gets admitted and when to deliver
What are the neonatal morbidites for praevia?
increased risk of lower 5‐minute Apgar scores, neonatal intensive care unit (NICU) admission, anaemia, respiratory distress syndrome, mechanical ventilation intraventricular haemorrhage.
What is the recommendation of tocolysis and praevia if TPTL with MI ?
If need to deliver for mum or baby then deliver
There is no evidence that tocolysis is harmful so a snr ob can consider it to get the steroids in
What is the risk of bleeding for different gestations with praevia
What is the RCOG advice for planning delivery timing
35 5%
36 15%
37 30%
38 60%
Delivery - tailored to situation:
Asymptomatic praevia 36-37 weeks
Symptomatic praevia 34-36+6
Is it possible to have a vaginal delivery with a low lying placenta?
Are there any factors that can help this decision making?
Poor evidence
The further away the thinner from the os the better (edge less then 10 mm)
Increased risk of LSCS is sponge like echo or marginal sinus
What are the factors associated with failure of a bakri to manage PPH from Praevia?
Prev LSCS
Anterior placenta
Thrombocytopenia / Coagulopathy at time of insertion
PPH of more then 500 mls within 1 hour of placement
Bakri works 75-88% of the time
Unexplained APH
Associated risks?
An epidemiological study of women with unexplained APH demonstrated an increased risk of oligohydramnios (OR 6.2), premature rupture of membranes (OR 3.4), fetal growth restriction (OR 5.6), preterm labour and caesarean delivery (OR 4.0). The authors concluded that women who have experienced APH should have increased fetal surveillance
throughout the pregnancy
What are the ways to categorise praevia?
Grade 1-4
1 - minor - low edge inside the lower segment
2 - marginal - lower edge reaching the os
3- partial - partially covering the os
4 - complete - coving the cx
Or From 16 weeks
low lying (less then 2cm from the cx)
or praevia - covering the cx
What are USS signs of accreta
A 2017 systematic review and meta‐analysis using the standardised ultrasound signs (see Appendix III) has shown that in women presenting with placenta praevia and history of prior caesarean section, the performance of ultrasound for the antenatal detection of placenta accreta spectrum is even higher with a sensitivity of 97.0% (95% CI 93.0–99.0), specificity of 97.0% (95% CI 97.0–98.0) and diagnostic OR of 228.5 (95% CI 67.2–776.9) in prospective studies.
Placental lacunae give the placenta a ‘moth‐eaten’ appearance on greyscale imaging and the increased vascularity of the placental bed with large feeder vessels entering the lacunae are the most common ultrasound signs associated with placenta accreta spectrum
Among the different ultrasound signs, abnormality of the uterus–bladder interface had the best specificity of 99.75% (95% CI 99.5–99.9) for the prediction of placenta accreta. Abnormal vasculature on CDI had the best predictive accuracy with a sensitivity of 90.74% (95% CI 85.2–94.7), specificity of 87.68% (95% CI 84.6–90.4) and diagnostic OR of 69.02 (95% CI 22.8–208.9)
What are the MRI signs of accreta
MRI has been increasingly used for the prenatal diagnosis of placenta accreta.145-149 The main MRI features of placenta accreta include abnormal uterine bulging, dark intraplacental bands on T2‐weighted imaging, heterogeneous signal intensity within the placenta, disorganised vasculature of placenta and disruption of the uteroplacental zone. A systematic review has found that most studies are of a small sample size and thus, sensitivity and specificity of MRI in diagnosing placenta accreta varies widely between 75% and 100%, and 65% and 100%, respectively
unexplained APH what are the fetal risks?
Still birth IUGR Oligo PTB Fetal anomalies Increased risk NICU admission PPROM LSCS
Incidence of cervical cancer in pregnancy?
1:10 000 woman
Provoked APH / vaginal discharge
