Multiple pregnancy

Question 1

What are the types of multiple pregnancy?

Answer 1

Dizygotic twins and monozygotic twins

Question 2

Are dizygotic or monozygotic twins more common?

Answer 2

Dizygotic twins (2/3rds of all multiple pregnancies)

Question 3

What are dizygotic twins?

Answer 3

Twins that result from fertilisation of different oocytes by different sperm. (unidentical)

Question 4

What are monozygotic twins?

Answer 4

Twins that result from mitotic division of a single zygote into ‘identical’ twins.

Question 5

Do monozygotic twins always share the same amnion or placenta?

Answer 5

No, it depends on the time at which division into separate zygotes occurred.

Question 6

What are dichorionic diamniotic (DCDA) twins?

Answer 6

Twins with separate placentas and amnions

Question 7

Are DCDA twins more common than MCDA (shared placenta, separate amnions)?

Answer 7

No, MCDA make up 70% of multiple pregnancies

Question 8

What are the risk factors for multiple pregnancies?

Answer 8

Assisted conception, genetic factors and increasing maternal age and parity are the most important factors, largely affects DZ twinning.

Question 9

What are the clinical features of multiple pregnancy?

Answer 9

Vomiting may be more marked in early pregnancy. The uterus is larger than expected from the dates and palpable before 12 weeks.

Question 10

What are the maternal antepartum complications of multiple pregnancy?

Answer 10

Gestational diabetes, PE, anaemia (due to dilution effect and partly because more iron and folic acid are needed)

Question 11

What are the fetal antepartum complications of multiple pregnancy?

Answer 11

Greater mortality (six fold) and long-term handicap (five fold); preterm delivery; IUGR; congenital abnormalities

Question 12

What are the complications of monochorionicity?

Answer 12

Largely from shared blood supply of single placenta: twin-twin transfusion syndrome; IUGR; co-twin death.

Question 13

What is twin-twin transfusion syndrome (TTTS)?

Answer 13

Results from unequal blood distribution through vascular anastomoses of the shared placenta. One twin ‘the donor’ is volume depleted and develops anaemia, IUGR and oligohydramnios. The other ‘recipient’ twin gets volume overloaded and may develop polycythaemia, cardiac failure and massive polyhydramnios.

Question 14

What are the risks of TTTS?

Answer 14

Both twins are at a very high risk of in utero death or severely preterm delivery. Survival of both twins is only 50%.

Question 15

What is co-twin death?

Answer 15

If one of an MC twin pari dies, either due to TTTS or any other cause, the drop in its blood pressure allows acute transfusion of blood from one to the other one, which leads to raid hypovolaemia and , in about 30% of cases death

Question 16

What are the intrapartum complications of multiple pregnancy?

Answer 16

Malpresentation of the first twins; fetal distress in labour; PPH

Question 17

Is the second twin at more risk than the first one?

Answer 17

Yes (five fold increased risk of death), due to hypoxia, cord prolapse, tetanic uterine contraction (>90s) or placental abruption.

Question 18

How can chorionicity be determined on US?

Answer 18

In first trimester, in dichorionic twins, the dividing membrane is thicker as it meets the placenta and in monochorionic twins the dividing membrane is thin and perpendicular to the shared placenta.

Question 19

What is the Lambda and the T sign in chorionicity?

Answer 19

Lambda sign - thick diving membrane, dichorionic twins

T sign - thin dividing membrane, monochorionic twins

Question 20

When and how is TTTS most commonly diagnosed?

Answer 20

Between 16 and 22 weeks, either by careful US including for tricuspid regurgitation or polyhydramnios

Question 21

How do you treat TTTS?

Answer 21

Expect where the disease is very mild, laser photocoagulation of the placental anastomoses in a fetal medicine centre, using US and fetoscopy

Question 22

How are multiple pregnancies delivered?

Answer 22

Increasingly using C section, even for uncomplicated twins due to increased risk to second twin.

Question 23

When are twins induced?

Answer 23

37 weeks with DCDA twins
36 weeks with MCDA twins
32+0 and 33+6 weeks with MCMA twins

Question 24

What analgesia is used in twins?

Answer 24

Epidural is not mandatory but is helpful if difficulty is encountered with the second twin.

Question 25

Do contractions alter after the first twin?

Answer 25

They are often diminished after the first twin, but usually return within a few minutes, oxytocin can be started if not

Question 26

Is the second twin easier to deliver than the first.

Answer 26

Usually, yes