Multiple pregnancy

Question 1

What are the 2 main types of twin pregnancies? How do they differ?

Answer 1

Dizygotic twins - 2 eggs, 2 sperm

Monozygotic twins - 1 egg, 1 sperm and mitotic division.

Question 2

What determines whether twins share a placenta and amniotic sac? What are the different types?

Answer 2

When they undergo mitotic division to separate.

Before day 3 = dichorionic diamniotic (DCDA)
Between days 4 and 8 = monochorionic diamniotic (MCDA)
Day 9-13 (later division) = monochorionic monoamniotic (MCMA)

Question 3

What causes conjoined twins?

Answer 3

Incomplete division

Question 4

What are some maternal symptoms of twin pregnancy?

Answer 4

Vomiting is more marked
Large for gestational age
3 or more foetal poles may be felt later in pregnancy

Question 5

What diagnoses twins?

Answer 5

Ultrasound

Question 6

What are maternal risks of twin pregnancy?

Answer 6

Risk of pre-eclampsia and gestational diabetes is increased. As in anaemia due to increased demand.

Question 7

All multiple pregnancy have a greater mortality and morbidity. Why?

Answer 7

Due to increased risk of IUGR, preterm delivery and monochorionicity.

Question 8

Which type of twin are congenital abnormalities more common in?

Answer 8

In monochorionic twins, congenital abnormalities are more common. They are not in dichorionic twins.

Question 9

What do you know about twins/multiple order pregnancy and miscarriage?

Answer 9

One can vanish in the first trimester when there is death. It is also more common late as well, especially when it is monochorionic, as a complication of twin-twin transfusion syndrome.

Question 10

What are the complications of monochorionicity?

Answer 10

Twin-twin tranfusion syndrome.
Twin anaemia polycythaemia sequence. 
Twin reversed arterial perfusion. 
Intrauterine growth restriction. 
Co-twin death. 
Monoamniotic twins.

Question 11

What is twin-twin transfusion syndrome?

Answer 11

Occurs only in MCDA twins. It results from uneven blood distribution through vascular anastomoses of the shared placenta.
One twin, the ‘donor’, is volume depleted and develops anaemia, oligohydramnios.
The other, the ‘recipient’, becomes volume overloaded and may develop polycythaemia, polyhydramnios and cardiac failure.

Question 12

What is the difference between twin-twin transfusion syndrome and twin anaemia polycythaemia syndrome?

Answer 12

TAPS occurs where there is a marked haemoglobin difference between MC twins but in the absence of liquor changes characteristic of TTTS.
TAPS occurs as a result of small placental anastomoses and can follow incomplete laser ablation for TTTS.

Question 13

What is twin reversed arterial perfusion?

Answer 13

It is a rare abnormality in twins where an abnormal, often acardiac, foetus is perfused by a normal ‘pump’ twin, which is therefore at risk of cardiac failure.

Question 14

What happens in co-twin death? What are the risk factors?

Answer 14

When one twin dies of MCDA twins, due to the sudden drop in its blood pressure, this allows acute transfusion of blood from the other twin. This rapidly leads to hypovolaemia and even death or neurological damage.

Question 15

Why are monochorionic monoamniotic twins at risk?

Answer 15

Their cords always tangle.

Acute shunting between the 2 babies in anastomoses due to close cord insertions is common.

Question 16

What are the complications of twin pregnancies?

Answer 16

Perinatal mortality increased fourfold
Preterm labour and miscarriage
Congenital abnormalities
Placental insufficiency/intrauterine growth restriction
Twin-twin transfusion syndrome
Antepartum and postpartum haemorrhage
Pre-eclampsia, diabetes, anaemia
Malpresentation

Question 17

When is chorionicity most accurately ascertained? What are the signs for each?

Answer 17

In the first trimester.
Dichorionic = membrane thicker as it meets the placentas and therefore has the lambda sign.
Monochorionic = thin membrane = T sign.

Question 18

What timings are recommended for delivery of monochorionic and dichorionic twins?

Answer 18

Dichorionic = 37 weeks is advised.
Monochorionic = 36 weeks is advised in non-complicated twins.

Question 19

When is twin-twin transfusion syndrome most commonly diagnosed? What is seen?

Answer 19

Between 16 and 24 weeks.
Growth and liquor volume differences are seen, with polyhydramnios evident. Evidence of fluid overload in the recipient and possibly tricuspid regurge.

Question 20

What is the treatment for twin-twin transfusion syndrome?

Answer 20

Laser ablation of the entire placental interface (using ultrasound and fetoscopy).

Question 21

In selective reduction of high order pregnancies or when one twin has an abnormality, how is termination carried out with the different twin types?

Answer 21

Dichorionic twins = KCl intracardiac injection (best done before 14 weeks)
Monochorionic = cord must be occluded or its insertion ablated because the circulation is shared between the twins.

Question 22

What type of delivery is recommended for twins?

Answer 22

If the first foetus is cephalic, vaginal birth should occur, no matter what the lie of the second foetus.
If the first foetus is transverse or breech, then caesarian section is indicated.

Question 23

In vaginal delivery, once the first twin has been delivered, what happens to contractions in the mother? What can you use to help?

Answer 23

The contractions often diminish but return within a few minutes. If they don’t, oxytocin can be started.

Question 24

In vaginal delivery, once the first twin has been delivered, what is checked in the second twin? What is done to help this if it’s wrong?

Answer 24

The lie of the second twin.
ECV is performed if it is breech and not longitudinal. Once the head or breech enters the pelvis, the membranes are ruptured again and pushing begins.

Malpresentation = caesarian section.