Multiple Gestation

Question 1

What are the 2 types of twins, and what is the aetiology of RF of each?

Answer 1

1 - MONOZYGOTIC:
Single fertilised egg that splits = ‘identical’.
(Earliest: 3 days) - dichorionic diamniotic.
(Early: 4-8 days) - monochorionic diamniotic
(Later: 8-12 days) - monochorionic monoamniotic
(Latest >12 days) - siamese twins.

• RANDOM OCCURRENCE
• not influenced by race, parity or family hx.
• Increased incidence in IVF.

2. DIZYGOTIC
   Release of 2 eggs at ovulation, both fertilised = ‘non-identical’.

Possible increased FSH increases it.

RF

• Race: 1. Nigerian 2. African 3. Caucasian 4. Oriental.
• advanced maternal age
• multiparity
• family height.
• increased height and weight.
• blood group O/A.

Question 2

What are the possible complications of Twin Gestation, to the mother and the baby?

Answer 2

RF

Management during pregnancy/birth.

Maternal

Increased hCG = Hyperemesis

• Increased placental mass = increased hCG
• Earlier and increased incidence.

Vigilance and awareness.

Increased blood volume (not official cause)

• Anemia
• Varicose veins
• Oedema

Early assessment of iron and folate supplementation.

FBC: 20-24 weeks gestation (as well as normal at 28 weeks).

Pre eclampsia

• 3-4x greater.
• Earlier and more severe.

Assess for additional RF.

If yes: take 75mg aspirin daily from 12 weeks until birth.

Increased placental SA

• Antepartum haemorrhage (placenta previa is more common – less space).
• Post partum haemorrhage.

As per normal pregnancy.

Greater hormone changes

• GDM

Intrapartum complications

• Delivery trauma
• C- section.

Post partum

• Psychological disorders
• Breastfeeding problems
• Parentcraft challenges.

Fetus

Chromosomal abormalities

Screening difficult and decreased efficacy:

• Amniocentesis: do each sac
• Chorionic villus – contraindicated – no guarantee that both placentae have been sampled.
• Difficult if abnormalities in only one fetus.

Counselling prior to any chromosomal testing.

Less space

• Premature birth

= 60% 〈 37 weeks (spontaneous)

–> increased uterine distension + early myometrial contractility.

• Fetal growth restriction

Single growth until 28-30 weeks.

Placental dysfunction.

Increased risk in monochorionic twins.

Present early if suspected labor: corticosteroids can be administered: accelerate fetal lung maturation.

Serial US: measure fetal abdo circumferences.

If IUGR dx – increased surveillance of fetal wellbeing (UA doppler, CTG) - optimal timing of delivery.

Monochorionic: lower threshold for devliery (adverse effects of single intrauterine death).

If one twin dies: other twin has 20% chance of death.

Fetal complications specific to monochorionic twins

Structural defects (due to dysfunction of embryo division).

• Neural tube defects
• Cardiac defects
• CNS defects
• Gastrointestinal atresia.

If one twin affected, other twin fine in 90% cases.

Detailed mid-semester scan (offered, not compulsary).

MX

• Selective termination (16-20weeks only).
• 5% risk that both are miscarried.

Twin-Twin-Transfusion Syndrome

Twin reversed arterial perfusion sequence

Question 3

How does twin gestation differ from singleton pregnancies?

Answer 3

x

Question 4

What is TRAP Syndrome? What is it’s

• Epidemiology
• Aetiology
• Management
• Complications
• Prognosis.

Answer 4

D: In the event that the heart of one twin stops, it continues to be partially perfused by the surviving twin.

Aetiology:

Large fetal arterial-arterial anastamoses exists in the shared placenta.

Result

Dead twin becomes ‘acardiac monster’ - atrophy of it’s upper body and heart (due to poor oxygenation of the tissues).

Complications

High incidence of mortality in the normal (pump) twin (from intrauterine cardiac failure and prematurity).

Risk is increased with increased size of the acardiac twin.

Management

Cord vessel occlusion on the acardiac twin if it is large (>50% size of normal twin) - improves survival rates of the normal twin.

Question 5

What is Twin Transfusion Syndrome? What is it’s

Aetiology

Epidemiology

Effects

Complications

Management

Prognosis

Answer 5

D: Net blood flow from one twin to another (monochorionic twins only)

Aetiology: Arterial-venous anastamoses within the placenta.

Epi: 15% of monochorionic pregnancies. 15% of perinatal mortality in twins.

Effects: The recipient becomes hyperdynamic, donor has low blood flow and ischemia.

Complications:

Recipient: High-output cardiac failure, polyhydramnios.

Donor: Oliguria (low urine output), oligohydramnios (low amniotic fluid), IUGR.

Pregnancy: Untreated - >80% pregnancy loss rate.

Management:

• Serial amniodrainage.
• Laser ablation of causative anastamosis (most successful).

Prognosis

No treatment: > 80% pregnancy loss rate.

Treatment:

At risk twin: Ablation = 70% survival, serial amniodrainage = 50% survival.

Surviving twin: Ablation = 5% neurological morbidity, serial amniodrainage = 15% neurological morbidity.

Question 6

What are the 2 main possible complications in Mono-amniotic twins?

Answer 6

1. Cord entanglement in utero.

(delivery planned for 32 weeks gestation, but earlier if cord compression suggested by abnormal fetal heart rate patterns on CTG).

2. TRAP.

Question 7

What are the consequences of twins with one fetal death?

Answer 7

Dichorionic:

First trimester/early second trimester: no adverse consequences for survivor.

Late second/third: precipitates labor. Prognosis depends on gestation.

Monochorionic

• complications due to shared fetal-placental circulation –> hypotension in co-twin at time of death.

Additional risk of death (20%)

Risk of cerebral damage (25%)