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Flashcards in RANZCOG questions Deck (12)
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1

a. List six risk factors for placenta previa. (3 marks)

Maternal pre-pregnancy factors:
• Previous placenta praevia
• Previous CS
• ‘Deficient’ endometrium – D&C, endometritis, MROP
• AMA
• Smoking

Fetal/obstetric factors:
• IVF/ART
• Multiple pregnancy

2

A 25 year old woman, at 20 weeks gestation in her second pregnancy, has a low-lying placenta on her routine morphology scan. You are seeing her to discuss this finding in a rural location and she wants to know her likelihood of having a placenta previa in the third trimester. She has not had any bleeding during this pregnancy.

b. What information at this point is useful to predict the likelihood that her placenta will remain low lying in the third trimester? Discuss three prognostic features in detail. (8 marks)

1. Anterior vs posterior – posterior placenta is more likely to remain low lying – anterior lower uterine segment grows more in third trimester
2. Previous CS – less likely to migrate. Also risk factor for accreta/increta/percreta - if the placenta is pathologically adherent to, or invasive of, the myometrium it is highly likely to remain that way
3. Whether covering the os completely or just low – significant migration unlikely if placenta substantially overlaps the so by >25mm

3

At 36 weeks gestation, her anterior placenta is found to cover the internal os on ultrasound scan. She has no antepartum haemorrhage and there is no evidence of placenta accreta.

c. List at least eight aspects of this delivery you will consider to optimise the outcome. (4 marks)

Pre-operative
• Planned elective procedure in tertiary centre with MDT involvement - obstetric, anaesthetics, blood bank, NICU, midwifery +/- interventional radiology
• Good quality images to determine likelihood of placenta accreta
• Optimise Hb
• Consider elective admission particularly as she is in a rural location
• Plan pre-labour CS – consider delivery during 38th week to minimize the risk of spontaneous labour
• Discussion and planning re: blood products – and plans in place if blood products declined, e.g. cell-saver, iron infusion
• Pre-operative discussion and consent include possibility of hysterectomy or interventional radiology if uncontrolled blood loss, and leaving placenta in situ if accreta. Discuss implications for future fertility.

Intra-operatively
• Valid G&S and X-matched blood available, consider cell saver
• Senior obstetrician
• Avoid incision of placenta if possible
• Anticipate PPH – active management of third stage and swiftly secure haemostasis
• Quick recourse to hysterectomy if excessive bleeding

4

You are obtaining consent from a primigravid woman with a major placenta praevia for an elective CS at 38 weeks gestation.
b. What serious risks should you discuss that may result from her operation and what is their chance of occurring? (7 marks)

• Anaesthetic risks
o GA
 Neonatal depression
 Uterine relaxation and increased bleeding
 Pulmonary aspiration of stomach contents
o Regional
 Hypotension
 Inadequate or failed block
 Respiratory depression
 Nausea and vomiting
 Need for GA if unsuccessful or procedure prolonged
• Surgical risks
o Emergency hysterectomy – up to 10%
o Heavy bleeding requiring transfusion – up to 20%
o Need for further operation following this 7%
o Developing venous thromboembolism 3%
o Injury to urinary system 6%
o Gastrointestinal injury <1%
o Risk of death with CS 1 in 12 000
o Increased risk ICU admission
o Infection
 Wound 2-16%
 Endometritis 35-40% overall if no prophylactic antibiotics, depends on CS after prolonged labour (up to 85% if no prophylactic antibiotics), CS with intact membranes (4-5%)
 Endometritis rate reduced by 60% with prophylactic antibiotics
• Future risks
o Stillbirth in future pregnancies 1-4 per 1000
o Placenta praevia in future pregnancy 2%
o Increased risk of tear of uterus in future pregnancies 2-7 per 1000
o Adhesion formation 12%
• Neonatal risks
o Admission to neonatal intensive care – risk depends on the gestation and if pre caesarean steroids are given. 3% risk for “term babies”

5

c. Discuss aspects of this particular delivery you will consider to optimise the outcome. (3 marks) (Placenta praevia q)

• MDT planning of delivery – anaesthesia, obstetrics (consultant), neonatal unit, haematology and blood bank informed of risk of massive obstetric haemorrhage
• Notify ICU in case needed post op
• Anaesthetics
o 2 large IVLs
o Cross-match blood
o Optimise pre-op Hb
o Discuss whether regional or GA
o Consider cell saver after delivery of placenta
• Surgery
o Avoid incising through placenta
o If problems with bleeding intraoperative call for extra help if required (another consultant)
o Liberal use of uterotonics to control bleeding
o Consider use of B-lynch suture, uterine or internal iliac artery ligation if ongoing bleeding
o Early recourse to hysterectomy if bleeding uncontrolled
• Interventional radiology
o Can consider putting uterine artery catheters in prophylactically pre surgery to inflate if haemorrhage
• Neonatal issues
o Unless significant antepartum haemorrhage, CS for placenta praevia should be done after 38 weeks
o Consider antenatal steroids if <39 weeks gestation to reduce respiratory distress in infant

6

A 23 year old primigravida has just had a fetal morphology scan performed at 20 weeks. The report stated that the placenta was posterior, low lying and that vessels were observed at the internal os. The fetus is otherwise well.

a) List the differential diagnoses. (2 marks)

• Vasa praevia
• Cord presentation
• Marginal placental sinuses
• Membrane separation
• Associated with velamentous cord insertion
• Associated with succenturiate placental lobe

7

A 23 year old primigravida has just had a fetal morphology scan performed at 20 weeks. The report stated that the placenta was posterior, low lying and that vessels were observed at the internal os. The fetus is otherwise well.

b) Discuss what you would advise the patient at this stage. (4 marks)

• Needs TVUSS with colour Doppler to further qualify – consider tertiary level scan to confirm
• If vasa praevia confirmed – potential risk to fetus if SROM/PTB/bleed – possible exsanguination
• Small chance (15%) that position of vessels will change – re-scan in T3
• Suggest elective admission in 3rd trimester in case of bleeding to allow timely delivery by C/S
• If managed as an outpatient - do not travel far from hospital, keep phone handy and stay with others
• If bleeding/SROM/pain occurs in community – call ambulance
• Avoid intercourse
• Will need delivery by Caesarean section

8

(vasa praevia)
c) She presents at 32 weeks with painful contractions but no bleeding. What is your management plan? (9 marks)

• Setting – manage in 3’ centre with NICU and blood bank available – transfer only if stable if necessary
• Get help- senior obs/anaesthetics/midwifery. OT/NICU.
• IVL, G&S, X-match, FBC
• NBM until stable
• CTG – if fetal distress Cat 1 CS, if no fetal distress, as below
• Further history
- strength/freq of contractions – increasing or decreasing?
- ROM?
- Abdo pain between contractions?
- FM’s
- PMHx, surgical, meds, allergy
• Examination
- Palpate contractions
- Speculum to assess cervical dilation – high risk bleed if dilating +/- fFN
- USS + colour doppler if time to check for persistence of vasa praevia and identify vessels pre-op
• Antenatal corticosteroids - potential for spontaneous or iatrogenic PTB
• Tocolysis until steroids complete
• If stabilized – keep for observation until delivery
• If fetal compromise, ongoing contractions or SROM then high risk bleeding – consider delivery by CS with blood available for baby
• Paeds at delivery – if SROM/bleed then the bleeding is fetal – prepare for immediate transfusion

9

You arrange admission to hospital for a 34 year old multiparous woman, at 30 weeks gestation with an antenatally diagnosed Type 1 vasa praevia. This was diagnosed at her routine morphology scan at 19 weeks gestation. She has had no bleeding this pregnancy and her previous pregnancy resulted in a normal term delivery. With respect to her antenatally diagnosed vasa praevia:
(i) Describe the two (2) features that would have been visualized at her routine morphology scan that alerted the sonographer to the increased risk of a Type 1 vasa praevia, and enabled further investigation. (2 marks)

• Aberrant fetal vessels within 2cm or crossing the cervix- seen with passing probe over the area on TV scan and using doppler flow to confirm fetal vessels present
• Placental/cord abnormalities: velamentous cord insertion into the placenta is a characteristic of type 1 vasa praevia and type 2 occurs with a velamentous fetal vessel connecting the placenta to a succinuriate placental lobe
o Risk factors for vasa praevia: bi-lobed and succinturiate placental abnormalities, placenta praevia, history of low-lying placenta in the second trimester, IVF, multiple pregnancy

10

(ii) Outline the details that you would expect to see on the morphology scan report that would reassure you of an accurate diagnosis of vasa praevia. (4 marks)

• The scan was performed by a qualified sonographer and read by a radiologist with experience in reporting placental abnormalities
• Both TA and TV scans were performed- TV scans are more accurate for diagnosis of vasa praevia
• Careful documentation of the placental location with regards to the os
• Careful documentation of any accessory lobes, their relationship to the main body of the placenta, and the documentation of the location fetal vessels
• Documentation that the umbilical cord is not in the area of the cervix and thus not what is being seen on USS (cord presentation)
• Diagnostic criteria for VP
o Visualising aberrant lineral or tubular echolucent structures with 2D imaging within 2cm of os
o Demonstrating blood flow in these structures using colour or power Doppler
o Demonstrating umbilical arteria/venous doppler waveforms using a pulse wave Doppler
o Aberrant vessels located over or within 2cm of the internal os attached to the inner perimeter of the fetal membranes

11

iii) Identify two (2) significant benefits of antenatal detection of vasa praevia for this pregnancy. (2 marks)
Justify her admission to hospital. (2 marks)

Benefits of antenatal detection
• Antenatal surveillance: vasa praevia can be associated with other placental abnormalities and there is a risk of growth restriction with velamentous cord insertion- regular USS can be performed to monitor for growth restriction
• Planning for delivery: the mode of delivery needs to be by lower-segment Caesarean section and this may need to be an emergency procedure if there is any bleeding
• Significant reduction in perinatal mortality and morbidity
o Overall perinatal mortality is 36%, compared with 97% survival with prenatal diagnosis
Justify admission to hospital
• There is an increased risk of tearing of the fragile vessels as the uterus grows and the lower segment stretches in the third trimester
• If there is tearing of the vessels and an APH, then a Caesarean section will need to be performed immediately as the baby may exsanguinate and die
• If she is in hospital then this can be performed much faster than if she were at home and had to call an ambulance to come in
• Allows immediate access to neonatal care and transfusion

12

Outline your management plan following admission. (5 marks)

Valid group and hold and IVL at all times, in case of need for emergency LSCS
• Explain procedure for emergency LSCS and sign consent to ensure that this is completed in cause of emergency
• Regular growth scans- every 2 weeks from 34 weeks to monitor for growth restriction
o Vessel mapping can also be done to attempt to avoid inadvertent injury to fetal vessels at LSCS
o Evaluate if vasa praevia has moved out of the way
• Scheduling of planned CS between 34-35 weeks (no later than 37 weeks) with aim to avoid labour prior to LSCS
• Daily CTG monitoring
• Encourage woman to mobilise and give her compression stockings to wear to reduce her risk of VTE due to immobility
• Education of the woman that she should call for review immediately should she have any bleeding, ROM, signs of labour or concern about her baby's movements
o Immediate CTG and prepare for delivery if any of these occur
• Administration of corticosteroids for fetal lung maturation in anticipation of potential preterm delivery
• Ensure the hospital has paediatric expertise and an appropriate level of neonatal care