MCDA Twin Pregnancy

1. MCDA
Supervisor: Dr Rafaie
Presenter: Tan Lee Na
19th September 2014

2. Are twins good?

7. Introduction
 Both babies share one placenta
 1/3 of twins in the UK have MC
placentas
 Recent increase in multiple
pregnancies due to ART
 Particular challenges: vascular
placenta anastomoses that are almost
universal and connect umbilical
circulation of both twins

9. Diagnosis: first trimester
Chorionicity and amnionicity: best accuracy in
1st trimester

10. MCDA

11. Diagnosis:
second trimester
A photographic record should be
retained

12. MCDA
Bidirectional arterio-arterial anastomosis

13. If unable to determine chorionicity,
treat as monochorionic until
proven otherwise

14. Dating
 Use the largest baby to estimate gest
age to avoid risk of estimating it from a
baby with early growth pathology
 Assign nomenclature: transverse (left
or right) or vertical (upper or lower)

15. Management: first trimester
 First trimester screening for
aneuploidy
 Anatomical survey
 ?prediction of MCDA complications

16. First trimester aneuploidy
screening:
 Offer information:
- greater likelihood of T21 in multiple
pregnancies
- different options for screening (problem with
biochemical screening)
- false positive rates of screening tests are
higher in multiple pregnancies
- higher rate of complications of invasive tests
(threshold for invasive test is higher)
- implications relating to selective fetal
reduction

17. Aneuploidy screening
 1st trimester screen: combined test (NT +
bHCG + PAPP-A)
 Calculate the risk per pregnancy for
monochorionic twins (as opposed to risk
per baby for dichorionic twins)
 If unable to do, consider 2nd trim serum
screening, however potential problems
arise such as double invasive testing
because risk of T21 cannot be calculated
separately for each baby

18. Subsequent Management
 Aim
◦ Timely detection of TTTS
◦ Detection of other complications such as
selective IUGR, TOPS, TRAPS, single fetal
demise

19. TTTS
Vascular Anastomoses
 95% monochorionic placentas have
these but only 10-15% suffer adverse
outcomes
 TTTS and TRAP are the most well
recognised complications
 Suggested aetiology: deep
anastomoses within placental mass
are usually btwn arteries and veins
which allow unidirectional blood flow

21. Suggested aetiology: cont..
 Endocrinal imbalance, donor twin has
hypovolaemia  RAS activation 
increased ADH  vasoconstriction
oliguria and AF
 Recipient twin: hypervolaemia  atrial
natriuretic peptide  polyuria and 
AF, also BP leading to cardiac
failure and hydrops, eventually death

22. TTTS

23. Quintero Staging System
Stage I: The fetal bladder of the donor twin remains visible
sonographically. Discrepancy in AFV with MVP ≤2 cm in
one sac and MVP ≥8cm (<20 weeks) or ≥10 cm (>20
weeks) in the other sac
Stage II: The bladder of the donor twin is collapsed and not
visible by ultrasound.
Stage III: Critically abnormal fetal Doppler studies noted.
This may include absent or reversed end-diastolic velocity
in the umbilical artery, absent or reverse flow in the ductus
venosus, or pulsatile flow in the umbilical vein.
Stage IV: Fetal hydrops present.
Stage V: Demise of either twin.

24. TTTS: How to diagnose?
 Can we predict TTTS in first trimester?
◦ CRL and NT discrepancy at 11-14 weeks: CRL
discrepancy marker for subsequent sFGR, NT
discrepancy not predictive
◦ NT: discordance >20% shows risk of severe
TTTS is > 30%, if <20% then risk of TTTS <
10%
◦ CRL: discordance >10% predictive of early
onset disease <20 weeks
ISUOG
6 Oct 2010: Intertwin CRL discrepancy in MC twins is an early feature of GR rather than TTTS
20 Apr 2007: Discordance in NT in the prediction of severe TTTS
31 Aug 2006: First trimester discordance in CRL predicts timing of development of TTTS

25. TTTS: Ultrasound Features
 Discordant growth
 Discordant liquor
◦ Donor MVP < 2cm
◦ Recipient MVP >
8cm
 +/- discordant
bladder size
 +/- abnormal
doppler in one or
both twin.
 +/- fetal hydrops or
fetal demise

26. BUT………………
 In severe early TTTS, the prominent
feature is discordant liquor
Growth may not be
significantly affected in
early pregnancy

27. Frequency of follow up
 Booking by 10 weeks
 At least 9 antenatal appointment
 At least 2 appointments with specialist
obstetricians
 Dating scan followed by scans at
16,18,20,22,24,28,32,34 weeks

28. Why do we need to detect early
TTTS?
 If left untreated, fetal mortality can
reach 80%, survivors face significant
risk of long term cardiac, renal and
neurological sequelae
 Timely intervention can save lives!!!
(one or both babies)

29. Management options of early
severe TTTS
Amnioreduction
Septostomy
Selective laser ablation of
communicating vessels

30. Management cont..
 Amnioreduction: survival rates 60-65%
 Septostomy: decrease in need to rpt
procedure and survival rate similar,
however risk of inter-twin cord
entanglement
 Laser ablation: most logical therapeutic
approach, placental vessels traced
endoscopically from origins and ablate
all anastomoses, survival rate 70-81%,
consider in ALL stages of TTTS to
improve perinatal outcome

31. TTTS occurs at later part of
pregnancy: management options
 Expectant
 Serial amnioreduction
Decide timing of
delivery!

32. Recommendation (RCOG)
 Severe TTTS presenting < 26 weeks
should be treated by laser ablation
rather than amnioreduction or
septostomy
 Little information about maternal
morbidity after laser
 Suggestion: USG (brain imaging, fetal
measurement, doppler) at least
weekly, consideration to deliver at 34
weeks, usually by CS

33. Complications of laser
ablation
 Most common: PROM (9%)
 Placental abruption 1%
 Miscarriage 8%
NICE March 2006

34. Monochorionic placenta

35. Twin Anaemia Polychytemia
Sequence (TAPS)

36. Twin Anaemia
Polychytemia Sequence
(TAPS)
 Monochorionic Twin (5%)
 Spontaneous or after incomplete Laser
treatment for TTTS
 Same pathology as TTTS (Milder form)
 Large intertwin hemoglobin differences in
the absence of amniotic fluid discordances
 Usually in 3rd trimester.

37. Presence of arterial-arterial anastomoses is protective
against TTTS
In TAPS: either less A-V anastomoses or more A-A
anastomoses

38. TAPS: Antenatal Diagnosis
 No apparent growth and liquor
discordance
 Main feature: discordance in MCA
blood flow
 MCA Peak systolic velocity
measurement (PSV)
◦ Moderate to severe anaemia: PSV MoM >
1.5
◦ Polycythaemia: PSV MoM < 0.8
Even in apparently uncomplicated MCDA, it is
advised to do MCA doppler in every patient after 24
weeks

40. TRAPS (Twin reversed arterial
perfusion sequence)
 Also called acardiac
twinning
 High perinatal mortality of
the normal ‘pump’ twin due
to CCF and hydrops
 Treatment:
◦ Expectant
◦ Cord occlusion of the acardiac
twin if show evidence of heart
failure in the pump-twin

41. Selective IUGR in MCDA
 Differentiate from TTTS by absence of
polyhydramnios in one of the amniotic
sacs, although the small twin may
have oligohydramnios owing to
placental insufficiency
 Scans after 24 weeks to detect fetal
growth restriction

42. Discordant Growth*
 Abdominal Circumference difference >
20 mm
 EFW difference > 20%** ( Larger twin as
a reference)
 BPD > 6 mm
 FL > 6 mm
* Usually accompanied with abnormal UA
doppler
** Latest evidence suggests that difference
by 18% is significant

43. Why is MCDA different
compared to DCDA?
 Death in one twin may lead to death of
the other twin
 Neurological sequelae in surviving
twin
Importance of close monitoring and timely decision for
delivery!!!
• try to achieve good survival of both fetuses
• at least survival of one fetus with minimal neurological
sequelae

44. Single fetal demise
 Risk to surviving twin of death or
neurological abnormality is 12% and 18%,
respectively
 Risks are not restricted to MC pregnancies
with a prior diagnosis of TTTS
 Caused by acute haemodynamic changes
around time of death, as survivor
haemorrhaging part of its circulating volume
into the circulation of the dying twin leading
to hypotension and low perfusion and
eventually ischaemic end organ damage

45. Subsequent management
 Detailed counselling and record in case
notes
 Rapid delivery is unwise unless there are
significant CTG abnormalities or evidence of
anaemia in the survivor (MCA doppler) or if
fetal death occurs late in pregnancy
 Evidence of fetal compromise could
represent continuing damage to the brain
and other organs, therefore conservative
management is often appropriate

46. Management continued….
 Plan for brain imaging by 4 weeks to
establish whether serious cerebral morbidity
has occurred as such manifestation on CNS
are variable and takes up to 4 weeks to
occur
 Fetal MRI provides earlier and more detailed
information about brain lesions than USG
 If pre-viable: TOP is an option
 Timing of delivery: 34-36 weeks

47. ? Intervention to prevent
concordant fetal demise or
neurological sequelae
 If single fetal demise is diagnosed
early: intrauterine fetal blood
transfusion of the surviving twin may
be considered

48. Timing of delivery
 Deliver at 36-37, does not appear to be a/w
increased risk of serious adverse outcomes
 Appropriate to aim for vag birth unless there
are accepted, specific clinical indications for CS
eg twin one lying breech or previous CS
 60% of twins: spontaneous birth before 37
weeks
 Prolonging pregnancy beyond 38 weeks
increases risk of fetal death
 If elective birth declined, offer weekly
appointment with specialist obstetrician, offer
USG at each visit and perform biweekly
biophysical profile assessments, fortnightly
fetal growth scans

49. Take home
message!!

50. MCDA: its all about
discordance!!
TTTS Discordant liquor
Selective IUGR Discordant
growth
TAPS Discordant MCA
PSV
TRAPS/discorda
nt fetal
anomalies
discordant fetal
anomalies

52. Reference
 RCOG
 ISUOG
 NICE clinical guideline, Sept 2011,
Multiple pregnancy
 StratOG