RANZCOG - MCDA twin pregnancy Flashcards
What are the specific complications of MCDA twin pregnancy?
Twin to twin transfusion syndrome
selective fetal IUGR
death of one twin
twin reversed arterial perfusion (TRAP) sequence
when should chronicity be determined?
ideally on an USS before 14/40
What are the serial growth scan recommendations for an MCDA twin pregnancy?
fortnightly growth scan from 16/40 to assess for TTTS or selective fetal IUGR
What would you advise a woman with an MCDA twin pregnancy about the efficacy of aneuploidy screening?
- lower detection rate in twin pregnancy
- NIPT therefore advised (higher risk of getting inadequate fetal fraction though)
What is twin to twin transfusion syndrome
unbalanced blood flow from one twin to the other
AV/VA discordance of large vessels
donor twin has bigger or more AV anastamoses
the net flow of blood is from the donor to the recipient
What is the staging criteria for TTTS called and how many stages are there?
Quintero staging for TTTS
5 stages
What is stage 1 of the Quintero staging system?
- MVP in donor twin of <2cm, in recipient >8cm
MVP = max vertical pocket
What is stage II of the Quintero staging system for MCDA twin pregnancy?
absent bladder in donor twin
non visualisation of bladder in donor twin following 60 mins of monitoring
What is stage III of the Quintero staging system for TTTS?
- absent or reversed umbilical artery diastolic flow
- reversed DV a wave
- pulsatile umbilical vein flow
What is stage IV of TTTS as per Quintero staging system?
- hydrops in one or both twins
What is stage V or TTTS as per Quintero staging system?
- fetal demise of one or both twins
what are the management options available for TTTS?
- expectant or conservative management
- intentional septostomy (non longer used really)
- amnioreduction
- laser photocoagulation
- selective reduction
- termination
What are the benefits of amnioreduction?
- reduces intra-amniotic pressure
- reduces intravascular pressure
- improves placental blood flow
- reduces the incidence of pre term labour (and the complications of polyhydramnios)
What are the complications/risks of amnioreduction?
- risk of serial procedures being required
- PPROM
- infection
- abruptions
What are the complications/risks of amnioreduction?
- risk of serial procedures being required
- PPROM
- infection
- abruptions
What are the average survival rates for fetus that have undergone amnioreduction?
50-65%
Describe fetoscopic laser photocoagulation as a procedure
- usually performed between 17 and 26 weeks gestation (afterward might as well deliver babies!)
- USS guided placement of fetoscope
- laser introduced through fetoscope
- aim is to interrupt anastomoses causing TTTS
- functionally divides the placenta into two regions - each supplying one of the twins
‘dichorionisation’ of the monochorionic placenta
what are the survival rates following fetoscopic laser coagulation?
- perinatal survival 75%
- disease free survival 60%
- fetal death 20%
- severe neonatal morbidity 20%
- neurological impairment 8%
- neonatal mortality 3%
Describe twin anaemia polycythaemia sequence TAPS
- discordant fetal blood flow from one to the other
- small anastomoses (<1mm) therefore the result is a subtle transfusion
- donor twin - anaemia develops, recipient twin - polycythaemia
- MCA PSV is used to assess for fetal anaemia
How does the MCA PSV indicate anaemia?
- increased velocity
- the anaemia causes an increased cardiac output –> results in preferential shunting and reduced viscosities –> increased blood flow particularly cerebral blood flow
what are the management options for TAPS sequence?
- expectant, planned birth, laser photocoagulation, transfusion
What does acute feto-fetal transfusion syndrome refer to?
A sudden drop in pressure and/or heart rate of one twin resulting in a large uni-directional blood flow from the co-twin
may lead to brain injury or death
When does acute feto-fetal transfusion occur?
With the demise of one twin - transfusion from surviving to dead twin
- 20-30% risk of brain injury
- 15% risk of death
Transient bradycardia (i.e. with type III gratacos sFGR)
When does acute feto-fetal transfusion occur?
With the demise of one twin - transfusion from surviving to dead twin
- 20-30% risk of brain injury
- 15% risk of death
Transient bradycardia (i.e. with type III gratacos sFGR)
What is the incidence of sFGR in MCDA twin pregnancies and what is the definition?
- 10% of MC pregnancies
- EFW <10% and or discordance of >20%
What is the cause of sFGR?
- discrepancy in the share of placental territory
- inter-twin anastomoses
Describe the gratacos (USS) staging of sFGR in MCDA twin pregnancies
Umbilical artery doppler:
1 - normal doppler/raised but forward flow
2 - constant absent, or reversed EDF
3 - intermittent absent or reversed EDF (cycling)
What are the placental findings associated with gratacos type 1 sFGR?
unequal sharing
big anastamoses which compensate for unequal territory share
No/small AA
What are the placental findings associated with type II gratacos sFGR?
- very unequal sharing
- small anastamoses which can compensate but for shorter time than the big anastamoses in type 1
- No/small AA
What are the placental findings associated with Type III gratacos sFGR?
- very unequal sharing
- large AA, compensate for unequal territory share and prolong pregnancy but high risk of acute transfusion
What is the clinical course of MC pregnancies complicated by type I gratacos sFGR?
- relatively benign
- small weight discordance
- usually deliver >34
What is the clinical course of MCDA twin pregnancies complicated by gratacos type II sFGR?
- high risk of deterioration and IUD of FGR twin
- low risk of intrauterine brain injury of co-twin
- mean GA of delivery 29/40W
What is the clinical course of MCDA twin pregnancies complicated by gratacos type III sFGR?
- low risk of hypoxia for FGR twin
- can prolong pregnancy >32/40 but 10-15% risk of unexpected IUD of FGR twin and 10-15% risk of brain injury of co-twin (acute transfusion following demise)
How do you manage sFGR complicated MCDA twin pregnancies?
- growth fortnightly (routine)
- Umbilical and MCA doppler at least weekly
- If UAPI abnormal then include DV
- timing of birth decided by fetal wellbeing, interval growth, BPP, DV, and or computerised CTG
How do you manage MCDA type 1 gratacos pregnancy?
- outpatient management
- fortnightly growth USS
- delivery by 34-36 weeks
How do you manage type II and III gratacos MCDA twin pregnancy?
- in-patient management
- twice weekly doppler studies
- twice daily CTG
- corticosteroids
- delivery by 32/40
How do you manage a pregnancy complicated by IUD of co-twin?
- MCA PSV doppler for anaemia
- CTG
- expectant management
- offer MRI at 4-6 weeks
- neurodevelopment follow up
What does Twin reversed arterial perfusion sequence refer to?
MCDA twin pregnancy complicated by an acardiac twin, and a pump twin
The acardiac twin is perfused due to placental anastamoses from the pump twin
The acardiac twin - is poorly formed with either a poorly developed absent heart, upper body and head
The pump twin is at increased risk of high output cardiac failure/hydrops and IUD
What is the treatment for TRAP sequence?
not always required but if is required then <16/40 in tertiary centre with cord occlusion or interstitial laser
