Multiple pregnancy

Question 1

What is the epidemiology of multiple pregnancy

Answer 1

High prevalence- in the UK ~ 16 per 1,000 births
Rate is increasing with increased use of assisted fertility and rise in maternal age
Majority (97-99%) twin pregnancies

Question 2

How can multiple pregnancy be classified

Answer 2

Number of foetuses: twins, triples, quadruplets etc.
Number of fertilised eggs: zygosity
Number of placentae: chorionicity
Number of amniotic cavities: amnionicity

Question 3

What is the difference between monozygotic and dizygotic twins

Answer 3

Monozygotic: fertilisation of a single ovum and subsequent division → dichorionic diamniotic twins
Dizygotic: occurs from ovulation and fertilisation of 2 oocytes → non-identical

Question 4

Describe the chorionicity of dizygotic twins

Answer 4

Any dizygotic twin → ALWAYS DD → each foetus has its own placenta and amniotic sac
2 functionally separate placentae, BUT the placentae can fuse together and appear as a single placental mass
The two separate amniotic sacs are separated by a thick 3-layer membrane (fused amnion in the middle with chorion on either side)
There are NO vascular connections between the two placentae

Question 5

Describe the chorionicity of monozygotic pregnancies

Answer 5

Dichorionic diamniotic (25-30%): zygote division after fertilisation (day 3)

Monochorionic diamniotic: division after 3-6 days post fertilisation (2 sacs, thin dividing membrane with a single layer of amnion)

Monochroionic monoamniotic (2%): division between 6-9 days post-fertilisation

Conjoined twins: division after 13 days

Question 6

When will conjoined twins occur and what are the signs of conjoining

Answer 6

1 in 50,000 pregnancies
Division after day 13

Single placentation
No visible separating amniotic membrane
Inseparable foetal bodies.

Question 7

What are the risk factors for multiple pregnancy

Answer 7

Increasing maternal age
Assisted fertility treatment - IVF
Race - Afro-Caribbean
Family history
Nutrition
Personal hx

Question 8

What are the symptoms and signs of multiple pregnancy

Answer 8

Exaggerated pregnancy symptoms e.g. N&V (hyperemesis G.), heart burn
Greater abdominal distension
Increased physiology (CO, volume expansion, haemodilution, diaphragmatic splinting, weight gain, lordosis)

Question 9

What is the antenatal care for multiple pregnancies

Answer 9

MDT- specialist obstetrician, specialist midwife, sonographers
Diet, lifestyle and nutritional supplements:
- High dose of folic acid(5mg) may be needed
- Anaemia screening: FBC @ 20-24 weeks & 28 weeks → consider iron supplementation
Increased serial growth and doppler US assessments
Additional US at 10-13 weeks: viability, chorionicity, presence of amniotic membranes and thickness
Monitor for FGR from 24w onwards
Assess cervical length at 24 weeks (<25mm is a powerful predictor before 32 weeks

Question 10

What are the additional US requirements for Dichorionic Diamniotic Twin Pregnancy (Uncomplicated)

Answer 10

Offer at least 8 antenatal appointments with HCP from the core team
- At least 2 of these appointments should be with a specialist obstetrician
- Extra scans indicated with routine antenatal appointments if CRL 45-84mm (between 11+2-14+1 weeks)
- Extra scans 4 weekly from 20 weeks(20, 24, 28, 32, 36 weeks)
- Additional appointments at 16 weeks and 34 weeks

Question 11

What are the additional US requirements for Monochorionic Diamniotic Twin Pregnancy (Uncomplicated)

Answer 11

Women have at least 11 antenatal appointments with HCP from the core team
- At least 2 are with specialist obstetrician
- Extra scans indicated with routine antenatal appointments if CRL 45-84mm (between 11+2-14+1 weeks)
- Extra scans 2-weekly from 16 weeks (16, 18, 20, 22, 24, 26, 28, 30, 32, 34 weeks)
- Detailed cardiac scan
- If discordant for foetal anomaly, should be managed in foetal medicine centre

Question 12

What are the additional US requirements for triamniotic triplet pregnancy

Answer 12

Offer at least 9 antenatal appointments with HCP from core team
- At least 2 are with specialist obstetrician
- Extra scans indicated with routine antenatal appointments if CRL 45-84mm (between 11+2-14+1 weeks)
- Extra scans 2-weekly from 20 weeks (20, 24, 26, 28, 30, 32, 34 weeks)

Question 13

What are the signs on US of multiple pregnancy

Answer 13

Inverted T-sign- suggests MONOchorionic pregnancy
Lambda sign- suggests Dichorionic pregnancy

Crown-Rump Length is used to measure gestational age

Question 14

How is FGR screened/monitored in multiple pregnancies

Answer 14

From 24 weeks
Monitor weight discordance using ≥ 2 biometric parameters and amniotic fluid levels
- Discordance >20%: increase to weekly in the 2nd/3rd trimester + UmbA doppler
- EFW or any baby <10th centile: increase to weekly in the 2nd/3rd trimester + UmbA doppler

If discordance >25% AND EFW is <10th centile → refer to tertiary foetal medicine centre

Question 15

What are the considerations for delivery in multiple pregnancy

Answer 15

Do USS when established labour to confirm location of twin and hearts, along with presentation of twins
Continuous CTG
Membranes ruptured as late as possible
Vaginal delivery may be used in uncomplicated DCDA pregnancies where the presenting baby is cephalic (even if second is breech)
Common practice is to offer induction of labour or elective caesarean at:
- 37 weeks of gestation in DC twins
- 36 weeks of gestation in MC pregnancies
- 32-33+6 weeks of gestation in MCMA– usually ELCS
Active management for 3rd stage

Question 16

What is the expected amount of time between delivery of each foetus

Answer 16

20 minutes
Provided the babies are continuously monitored, an increasing birth interval between first and second twins is not associated with poorer outcome

Question 17

What is the management for delayed delivery of the second feoetus

Answer 17

> 20 minutes
Internal podalic version and breech extraction is the preferred primary procedure, achieving higher success rates than ECV (96%) with no increase in neonatal morbidity.
Internal podalic version- find a foetal foot through intact membranes, grasp and gently pull continuously into the birth canal

Question 18

How is selective termination of monochorionic twins carried out

Answer 18

Occlusive technique is needed to prevent exsanguination of the surviving twin along with placental vascular anastomoses in the dead twin
Bipolar diathermy of the affected twin’s cord is currently the most preferred technique

Question 19

How is selective termination of dichorionic twins carried out

Answer 19

The lack of placental anastomoses means that selective fetocide can be performed using USS guided injection of potassium chloride into the foetal heart.
Expectant management may be preferable for lethal abnormalities in view of a 5-10% risk of loss of the healthy twin if fetocide is performed in the 1st or 2nd trimester

Question 20

What are the maternal risks/complications of multiple pregnancy

Answer 20

First trimester: anaemia exacerbation, worsened symptoms of pregnancy (morning sickness, heartburn, swollen ankles, varicose veins, backache and tiredness), deteriorating pre-existing health problems

Second trimester:
GDM
Gestational hypertension
Antepartum haemorrhage
Venous thromboembolism

Third trimester
Antepartum haemorrhage/postpartum haemorrhage
Preterm labour

Question 21

What are the foetal risks of multiple pregnancy

Answer 21

Perinatal morbidity and/or mortality
Cerebral palsy
FGR
Preterm birth
Cord entanglement
Stillbirth, Miscarriage

Monozygotic:
Congenital heart disease
Midline defects e.g. anencephaly, holoprosencephaly, neural tube defects and cloacal extrophy

Question 22

What are Vascular placental anastomoses

Answer 22

This ONLY occurs in monozygotic pregnancies where the placenta is SHARED
There are NO anastomoses within dichorionic pregnancies
Arterial-arterial, Venous-venous or Arterial-venous
Arterial-arterial is protective against TTTS

Question 23

What is twin to twin transfusion syndrome (TTTS)

Answer 23

Placental anastamoses → unbalanced transfusion → donor twin gives blood to recipient who will have an increased renal perfusion which increases urine output so this leads to polyhydramnios
10-15% of monochorionic (only) pregnancies
May lead to twin anaemia polycythaemia syndrome (TAPS) (amniotic fluid normal)

Question 24

How does TTTS present

Answer 24

2nd trimester with discordant amniotic fluid volume
US exam between 16 and 24 weeks focus on detecting this condition.
After 24 weeks the main purpose of ultrasound examinations is to detect fetal growth restriction.

Question 25

What is the management for twin to twin transfusion syndrome

Answer 25

Laser ablation
- The placental vessels are traced endoscopically from their respective origins and identified as arteriovenous, venous-venous or AAA.
- Survival rate approaching 70%
- Leave AAA but ablate the other 2 types

Question 26

What is Twin Reversed Arterial Perfusion Sequence

Answer 26

There is a large arterio-arterial anastomosis from a normal ‘pump co-twin’ to the ‘acardiac twin’
→ absent or rudimentary development of the head, heart and upper limb structures in the acardiac twin → force is so great that the heart of the other baby does not develop → none of the structures below the heart develop
→ pump twin may get high congestive F and hydrops

Question 27

What is the treatment for Twin Reversed Arterial Perfusion Sequence

Answer 27

Separation of the two foetal cardiovascular circulations, either by:
- Bipolar diathermy to occlude the cord
- Interstitial laser/ monopolar diathermy of a central vessel of the acardiac twin.

Question 28

What are the risks of IUD in single monochorionic twins and what should be done

Answer 28

There is 25% risk of neurological and renal lesions in the survivor twin
There is initially similar risk of IUD in the healthy co-twin
→ Acute haemodynamic imbalance → hypotension → subsequent ischaemia.
The initially healthy twin transfuses blood to the dead twin’s vasculature
Should wait and scan (MRI) for surviving twin with a time delay to see if there has been any compromise of the survivor

Question 29

What is the prognosis of multiple pregnancies

Answer 29

60% of twin pregnancies result in spontaneous birth < 37 weeks
Monochorionic twins have higher likelihood of preterm delivery than dichorionic
Monochorionic diamniotic pregnancies are at risk of twin-to-twin transfusion syndrome (TTTS) and twin anaemia-polycythaemia sequence (TAPS).
For twin pregnancies, the 2nd twin is at greater risk of intrapartum compromise than the presenting twin or a singleton
Monoamniotic twins have high perinatal loss and morbidity due to consequences of cord entanglement
3-fold increase in postpartum depression