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Laura MRCOG Part 2 > 8A) Antenatal Care: Multiple Pregnancies > Flashcards

8A) Antenatal Care: Multiple Pregnancies Flashcards

1
Q

What percentage of twins are monochorionic?

A

30%

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2
Q

What percentage of monochorionic twins are monoamniotic?

A

1%

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3
Q

Incidence of conjoined twins

A

1 in 100,000 pregnancies

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4
Q

What percentage of monozygotic twins will be dichorionic?

A

30%

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5
Q

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

A

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

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6
Q

When to scan for chorionicity?

A

11-13+6

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7
Q

Signs on scan for chorionicity

A

T sign for single placenta

Lambda sign for two placentas

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8
Q

Risk of TTTS

A

15%

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9
Q

What is TAPS?

A

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

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10
Q

Risk of TAPS

A

13% after laser treatment

2% in uncomplicated pregnancies

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11
Q

What is TRAP?

A

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

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12
Q

Risk of TRAP sequence?

A

1%

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13
Q

Risk of selective growth restriction

A

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

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14
Q

Definition of selective growth restriction

A

Difference in EFW >20%

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15
Q

Risks of monochorionic twins

A 
TTTS
TAPS
TRAP Sequence
Selective growth restriction
Single intrauterine death
Increased perinatal mortality
Chromosomal abnormalities 
Structural abnormalities (predominantly midline)
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16
Q

When to scan monochorionic twins?

A

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)

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17
Q

Quintero staging for TTTS

A
  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.
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18
Q

Management of TTTS

A
  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.

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19
Q

Recurrence rate after laser ablation

A

15%

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20
Q

When to deliver after ablation?

A

34-36 weeks.

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21
Q

Outcomes of laser treatment

A

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

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22
Q

Risk of death of surviving twin after single intrauterine death

A

15%

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23
Q

Risk of neurological abnormality in surviving twin after single intrauterine death

A

25%

24
Q

Management after single intrauterine death

A

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

25
Q

When to deliver uncomplicated MCDA twins?

A

36 weeks (aim NVD)

26
Q

When to deliver MCMA twins?

A

32-34 weeks (CS)

27
Q

Management of selective growth restriction

A
  • 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
28
Q

Types of selective growth restriction

A

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

29
Q

What percentage of twin pregnancies have a discordant abnormality?

A

1-2%

30
Q

How to do selective reduction in monochorionic twins?

A

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

31
Q

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

A

2.5 x increased

32
Q

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

A

3 x increased twins

9 x increased triplets

33
Q

What is the risk of stillbirth with multiple pregnancies?

A

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

34
Q

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

A

Singletons: 43%
Multiples: 65%

35
Q

What percentage of stillbirths is TTTS responsible for?

A

20%

36
Q

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

A

Singleton: 39%
Multiples: 66%

37
Q

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

A

5x more common

38
Q

What does the lambda sign show?

A

Dichorionic

39
Q

What does the T sign show?

A

Monochorionic

40
Q

What features on USS are used to determine chronicity?

A

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

41
Q

How often to scan dichorionic twins?

A

20, 24, 28, 32, 36.

42
Q

How often to scan triplets?

A

Mono/Di: Every 2 weeks from 16/40

Tri: 20, 24, 28, 32, 34

43
Q

What are the implications of multiple pregnancy on screening?

A

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

44
Q

What screening methods to offer in multiple pregnancies?

A

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.
45
Q

When should multiple pregnancies be delivered?

A

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

46
Q

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

A

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

47
Q

What percentage of all live births are twin pregnancies?

A

3%

48
Q

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

A

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

49
Q

What percentage of triplets deliver <35 weeks

A

75%

50
Q

What percentage of PTB in multiple pregnancies are iatrogenic?

A

1/3

51
Q

What percentage of special care unit admissions are twins?

A

15%

52
Q

What percentage of twins will require admission to special care?

A

44%

53
Q

What is the increased perinatal mortality rate in twins?

A

3 x increased compared to singletons

54
Q

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

A

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

55
Q

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

A

33% v 6%

56
Q

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

A

Nothing!

Laura MRCOG Part 2 (56 decks)

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