2016 51 Monochorionic Twins Flashcards
How is monochorionic twin pregnancy diagnosed?
- US 11-13+6
- By number of placental masses, appearance of membrane attachment to placenta, membrane thickness
How do the outcomes of monochorionic pregnancy compare to dichorionic?
- Higher fetal loss, esp 2nd trimester
- Neurodevelopmental morbidity
What ultrasound regime is recommended for monochorionic twins?
- Every 2 weeks from 16/40 if uncomplicated
- DVP, UAPI, fetal bladders, EFW, discordance
What is TAPS?
How is it screened for?
Twin anaemia polycythaemia sequence
Complication of LASER ablation for TTTS
MCA PSV
What level of growth discordance is associated with increased perinatal risk?
> 20%
What umbilical artery features are associated with perinatal M&M?
- Absent or reversed end-diastolic velocity
- Cyclical waveforms (intermittent AREDV)
What system is used to stage TTTS?
Quintero system
How should TTTS be managed?
<26/40:
LASER ablation, using Solomon technique
Weekly US for 2 weeks, then fortnightly
US examination of fetal hearts
Delivery 34-36+6/40
How should selected growth restriction be managed?
- Consider selective reduction
- Fortnightly Doppler surveillance
- Consider delivery if abnormal DV waveforms or cCTG
- Early delivery (separate card)
When should birth be planned on selective growth restriction?
- Type 1: 34-36/40
- Types 2 & 3: 32/40 or sooner if growth velocity significantly abnormal or worsening Dopplers
In monochorionic single twin demise, what are the risks of a) death & b) neurological abnormality for the other twin?
a) 15%
b) 25%
How can neurological abnormality in the surviving twin be detected after single twin demise?
MRI 4 weeks after demise
If this would inform Mx planning
How should fetal anaemia be monitored following single twin demise?
Doppler: MCA PSV
When & how should uncomplicated MCDA twins be delivered?
36/40
IOL unless other reason for CS
When & how should MCMA twins be delivered?
32-34/40
Due to higher risk of fetal death
What are the standards for centres managing monochorionic twins?
- Minimum 2 experienced operators
- More than 15 cases per year
What proportion of twin pregnancies are monochorionic?
30%
What complications are increased in twin pregnancies?
- Preterm birth
- FGR
- PET
- PPH
- Infant feeding difficulties
- Adverse puerperal mood change
What are the risks specific to monochorionicity?
- TTTS
- sGR
- TAPS
- TRAP
- Single intrauterine demise
What proportion of monochorionic twins are MCMA?
1%
In monochorionic twins, what proportion of vascular anastomoses are bidirectional?
80%
What proportion of monochorionic pregnancies are affected by TTTS?
15%
What proportion of monochorionic twins pregnancies are affected by TTTS?
Without TTTS: 15%
With TTTS: 50%
What are the 5 Quintero stages of TTTS?
I: significant discordance amniotic fluid volume; oligo <2cm donor, poly >8cm recipient (10cm after 20/40)
II: bladder of donor twin not visible
III: Dopplers abnormal in either twin
IV: ascites, pericardial or pleural effusion, scalp oedema, overt hydrops
V: one or both babies have died
How is TAPS characterised?
- Donor fetal anaemia
- Recipient polycythaemia
- Donor raised MCA PSV > 1.5 MoM
- Recipient low MCA PSV < 1.0 MoM
What are the types of sGR?
I: growth discordance but +ve diastolic velocities in both umbilical arteries
II: with AREDV in 1 or both twins
III: with cyclical UA waveforms
What is TRAP?
Twin reversed arterial perfusion sequence
Acardiac twin perfumed by cardiac twin through large arterial anastomoses
What proportion of twins are oriented laterally vs vertically?
90% lateral
10% vertical
What is the proportion of fetal loss at <24/40 in a) monochorionic, b) dichorionic pregnancy?
a) 14%
b) 3%
What is the perinatal mortality rate for a) monochorionic & b) dichorionic twins?
a) 12%
b) 5%
What is included in the combined screening for aneuploidy?
- Nuchal translucency
- β-hCG
- PAPP-A
What is included in the quadruple test for aneuploidy?
When should it be used?
- AFP
- β-hCG
- Unconjugated E3
- Inhibin A
Use after 14/40
What structural abnormalities are more common in twins than singletons?
Cardiac
What structural abnormalities are more common in monozygotic twins?
Midline:
1. Holoprosencephaly
2. Neural tube defects
3. Cardiac abnormalities
What are the survival rates of at least 1 twin for TTTS at different Quintero stages?
I: 91%
II: 88%
III: 67%
IV: 50%
How can selective termination in twin pregnancy be carried out?
Vaso-occlusive techniques:
1. Bipolar cord occlusion
2. Radiofrequency ablation
Not KCl due to anastomoses
What proportion of women with uncomplicated twin pregnancies give birth spontaneously before 37/40?
58%
What is the prevalence of conjoined twins?
1 in 100,000
What is the lambda sign/T sign indicative of?
Dichorionicity
