8A) Antenatal Care: Multiple Pregnancies

Question 1

What percentage of twins are monochorionic?

Answer 1

30%

Question 2

What percentage of monochorionic twins are monoamniotic?

Answer 2

1%

Question 3

Incidence of conjoined twins

Answer 3

1 in 100,000 pregnancies

Question 4

What percentage of monozygotic twins will be dichorionic?

Answer 4

30%

Question 5

When does the cleavage occur for MCDA, MCMA and conjoined twins occur?

Answer 5

MCDA: D4-D8
MCMA: D8-D13
Conjoined: D13-15

Question 6

When to scan for chorionicity?

Answer 6

11-13+6

Question 7

Signs on scan for chorionicity

Answer 7

T sign for single placenta

Lambda sign for two placentas

Question 8

Risk of TTTS

Answer 8

15%

Question 9

What is TAPS?

Answer 9

Caused by <1mm artery-vein anastomoses which allow slow transfusion of blood from donor —> recipient. Causes discordant Hb levels at birth without oligo/polyhydramnios.

Question 10

Risk of TAPS

Answer 10

13% after laser treatment

2% in uncomplicated pregnancies

Question 11

What is TRAP?

Answer 11

Acardiac twin being perfused by anatomically normal pump twin through large artery-artery anastomoses.

Question 12

Risk of TRAP sequence?

Answer 12

1%

Question 13

Risk of selective growth restriction

Answer 13

15% in absence of TTTS, 50% in presence of TTTS

Question 14

Definition of selective growth restriction

Answer 14

Difference in EFW >20%

Question 15

Risks of monochorionic twins

Answer 15

TTTS
TAPS
TRAP Sequence
Selective growth restriction
Single intrauterine death
Increased perinatal mortality
Chromosomal abnormalities 
Structural abnormalities (predominantly midline)

Question 16

When to scan monochorionic twins?

Answer 16

11-13+6: Dating, placenta, screening
18-20+6: Anomaly scan with extended views of fetal heart
Every 2 weeks from 16 weeks (16-26 primarily for TTTS, >26 for sGR)

Question 17

Quintero staging for TTTS

Answer 17

1. Significant discordance in amniotic fluid. DVP <2cm donor, >8cm (if less than 20 weeks) or >10cm (if more than 20 weeks) in recipient. Bladder visible and Doppler normal.
2. Bladder of donor twin not visible + severe oligohydramnios.
3. Doppler abnormal in either twin
4. Ascites, pericardial or pleural effusions, scalp oedema or hydrops
5. One or both babies died.

Question 18

Management of TTTS

Answer 18

1. Staging using Quintero and measure umbilical artery Doppler, MCA and DV

Under 26 weeks - fetoscopic laser ablation and then weekly scans (including MCA/DV Doppler) which can reduce to two weekly after two weeks.

More than 26 weeks - amnioreduction.

Question 19

Recurrence rate after laser ablation

Answer 19

15%

Question 20

When to deliver after ablation?

Answer 20

34-36 weeks.

Question 21

Outcomes of laser treatment

Answer 21

35-50% both surviving.
75% one surviving.
25% neither surviving.

Question 22

Risk of death of surviving twin after single intrauterine death

Answer 22

15%

Question 23

Risk of neurological abnormality in surviving twin after single intrauterine death

Answer 23

25%

Question 24

Management after single intrauterine death

Answer 24

Fetal MRI 4/52 after death if it will guide management.

Question 25

When to deliver uncomplicated MCDA twins?

Answer 25

36 weeks (aim NVD)

Question 26

When to deliver MCMA twins?

Answer 26

32-34 weeks (CS)

Question 27

Management of selective growth restriction

Answer 27

- If early onset, poor growth and abnormal Doppler - consider selective reduction. - Growth, uterine artery and MCA Doppler (and DV if UA abnormal) every 2 weeks - If DV abnormal or computerised CTG short term variation abnormal then consider delivery - If Doppler normal - delivery 34-36 weeks - If Doppler abnormal - delivery 32 weeks

Question 28

Types of selective growth restriction

Answer 28

Type 1 - Positive EDF Type 2 - Absent/Reversed EDF Type 3 - IAEDF

Question 29

What percentage of twin pregnancies have a discordant abnormality?

Answer 29

1-2%

Question 30

How to do selective reduction in monochorionic twins?

Answer 30

Cord coagulation or intrafetal ablation (can’t be via injection of abortifacient as circulations not independent)

Question 31

What is the increase in maternal mortality associated with a multiple pregnancy?

Answer 31

2.5 x increased

Question 32

What is the increase in maternal hypertensive disorders associated with a multiple pregnancy?

Answer 32

3 x increased twins | 9 x increased triplets

Question 33

What is the risk of stillbirth with multiple pregnancies?

Answer 33

Singleton: 5 per 1000 Twins: 12 per 1000 Triplets: 31 per 1000

Question 34

What percentage of NND is PTB responsible for in singleton pregnancies and in multiple pregnancies?

Answer 34

Singletons: 43% Multiples: 65%

Question 35

What percentage of stillbirths is TTTS responsible for?

Answer 35

20%

Question 36

What percentage of stillbirths are associated with IUGR in singleton pregnancies and in multiple pregnancies?

Answer 36

Singleton: 39% Multiples: 66%

Question 37

What is the increased risk of congenital abnormalities in multiple pregnancies?

Answer 37

5x more common

Question 38

What does the lambda sign show?

Answer 38

Dichorionic

Question 39

What does the T sign show?

Answer 39

Monochorionic

Question 40

What features on USS are used to determine chronicity?

Answer 40

Number of placental masses, lambda/T sign, membrane thickness.

Question 41

How often to scan dichorionic twins?

Answer 41

20, 24, 28, 32, 36.

Question 42

How often to scan triplets?

Answer 42

Mono/Di: Every 2 weeks from 16/40 | Tri: 20, 24, 28, 32, 34

Question 43

What are the implications of multiple pregnancy on screening?

Answer 43

Down's syndrome more likely. False positive more likely. Invasive screening more likely and complications from it are more likely.

Question 44

What screening methods to offer in multiple pregnancies?

Answer 44

11+0-13+6: - Twin: Combined screening (NT, bhCG, PAPP-A) - Triplet: NT and maternal age Second trimester: - Twin: Consider 2nd trimester screening but only gives 1 result for the pregnancy therefore may lead to double invasive testing. - Triplets: Don't use second trimester screening.

Question 45

When should multiple pregnancies be delivered?

Answer 45

MCMA: 32-34 weeks. Triplets: 35 weeks. MCDA: 36 weeks. DCDA: 37 weeks.

Question 46

What is the relative risk of fetal death associated with "post-maturity" in multiple pregnancies compared to singleton?

Answer 46

36-38 weeks multiple is equivalent to 42 weeks singleton. 40 weeks RR 4 42 weeks RR 9

Question 47

What percentage of all live births are twin pregnancies?

Answer 47

3%

Question 48

What percentage of twins deliver < 37 weeks, <34 weeks and < 32 weeks?

Answer 48

50-60% < 37 weeks 20% < 34 weeks 10% < 32 weeks

Question 49

What percentage of triplets deliver <35 weeks

Answer 49

75%

Question 50

What percentage of PTB in multiple pregnancies are iatrogenic?

Answer 50

1/3

Question 51

What percentage of special care unit admissions are twins?

Answer 51

15%

Question 52

What percentage of twins will require admission to special care?

Answer 52

44%

Question 53

What is the increased perinatal mortality rate in twins?

Answer 53

3 x increased compared to singletons

Question 54

In asymptomatic women with multiple pregnancy what is the best predictor of birth <28 weeks?

Answer 54

Cervical length <30mm at 18 weeks (NICE don't recommend)

Question 55

What is the risk of PTB in asymptomatic women with multiple pregnancy and positive FFN?

Answer 55

33% v 6%

Question 56

What has been shown to be of benefit in reducing PTB rates in multiple pregnancies?

Answer 56

Nothing!