MCDA

Supervisor: Dr Rafaie

Presenter: Tan Lee Na

19th September 2014

Are twins good?

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

Diagnosis: first trimester

Chorionicity and amnionicity: best accuracy in

1st trimester

MCDA

Diagnosis:

second trimester

A photographic record should be

retained

MCDA

Bidirectional arterio-arterial anastomosis

If unable to determine chorionicity,

treat as monochorionic until

proven otherwise

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)

Management: first trimester

First trimester screening for

aneuploidy

Anatomical survey

?prediction of MCDA complications

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

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

Subsequent Management

Aim

◦ Timely detection of TTTS

◦ Detection of other complications such as

selective IUGR, TOPS, TRAPS, single fetal

demise

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

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

TTTS

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.

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

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

BUT………………

In severe early TTTS, the prominent

feature is discordant liquor

Growth may not be

significantly affected in

early pregnancy

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

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)

Management options of early

severe TTTS

Amnioreduction

Septostomy

Selective laser ablation of communicating vessels

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

TTTS occurs at later part of

pregnancy: management options

Expectant

Serial amnioreduction

Decide timing of

delivery!

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

Complications of laser

ablation Most common: PROM (9%)

Placental abruption 1%

Miscarriage 8%

NICE March 2006

Monochorionic placenta

Twin Anaemia Polychytemia

Sequence (TAPS)

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.

Presence of arterial-arterial anastomoses is protective

against TTTS

In TAPS: either less A-V anastomoses or more A-A

anastomoses

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 < 0.8Even in apparently uncomplicated MCDA, it is

advised to do MCA doppler in every patient after 24

weeks

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

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

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

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

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

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

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

? 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

Timing of delivery

Deliver at 36-37, does not appear to be a/wincreased 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

Take home

message!!

MCDA: its all about

discordance!!

TTTS Discordant liquor

Selective IUGR Discordant

growth

TAPSDiscordant MCA

PSV

TRAPS/discorda

nt fetal

anomalies

discordant fetal

anomalies

Reference

RCOG

ISUOG

NICE clinical guideline, Sept 2011,

Multiple pregnancy

StratOG