MULTIPLE PREGNANCY

Question 1

What is the incidence of twin pregnancy?

Answer 1

1 in 80 pregnancies

Question 2

What is the incidence of spontaneous triplets?

Answer 2

1 in 6400 pregnancies

Question 3

What factors increase the likelihood of having a multiple pregnancy?

Answer 3

Increasing maternal age

Increasing parity

More common in African

Improved nutrition

Assisted conception

Question 4

How and when are multiple pregnancies usually diagnosed?

Answer 4

Routine dating ultrasound scan at 11-14 weeks

Question 5

What percentage of twins are dizygotic?

Answer 5

75%

Question 6

What is the most important clinical issue to work out on discovery of twins?

Answer 6

The chorionicity of the pregnancy

Question 7

What is chorionicity?

Answer 7

How many placenta there are for the twins - ie whether they are sharing or not.

Question 8

What is the risk of monochorionic twins?

Answer 8

Unequal distribution of blood leading to growth restriction of one twin and macrosomia in the other

Question 9

Are monochorionic twins always monozygotic?

Answer 9

Yes.

Question 10

Are monozygotic twins always monochorionic?

Answer 10

No. It depends at what stage in cell replication the split occurs.

1/3 happen in the 8 cell stage and these twins will be dichorionic, like dizygotic twins.

2/3 happen days 3-8 and are therefore monochorionic but diamniotic, as the inner mass splits to form two seperate membranes.

A small proportion happen between days 8-13 and are therefore monochorionic monoamniotic.

Question 11

Are most triplets monozygotic or trizygotic?

Answer 11

Neither. Most triplets come from originally two fertilised ova, where one of them splits to form monozygotic twins.

Question 12

How do work out the chorionicity antenatally?

Answer 12

USS before 16 weeks gestation

Question 13

What is the name of the sign seen on USS in dichorionic twins?

Answer 13

Lambda

Question 14

What is the name of the sign seen on USS in monochorionic diamniotic twins?

Answer 14

T sign

Question 15

How might you work out the zygosity of twins on USS?

Answer 15

Chorionicity

Different sexs

Question 16

What are the risks and complications of multiple pregnancies?

Answer 16

Increased risk of any complication associated with singleton pregnancy - gestational diabetes; pre-eclampsia or pregnancy induced hypertension

Increased chance of fetal malformation

Intrauterine growth restriction (IUGR)

Preterm labour

Increased chance of antepartum haemorrhage (placenta abruption and praevia)

Twin-to-twin transfusion syndrome

Increased chance of postpartum haemorrhage

Locked twins

Question 17

What is the problem of finding fetal abnormalities in only one of the two twins?

Answer 17

Selective fetocide can result in the miscarriage of the apparently normal fetus as well as the abnormal one.

Question 18

How should antenatal care be increased in mothers with multiple pregnancy?

Answer 18

Serial USS every 2 to 4 weeks to exclude IUGR - especially important with monochorionic placentation.

Question 19

In what proportion of multiple pregnancies does preterm labour occur?

Answer 19

30%

Question 20

What can be used as a screening tool to work out likelihood of preterm labour in a woman with multiple pregnancy?

Answer 20

Cervical length screening by transvaginal ultrasound

Question 21

How might preterm labour be prevented in higher order multiple pregnancies?

Answer 21

Elective cervical suture at the start of the second trimester

Question 22

How do you manage a woman with multiple pregnancy who goes into preterm labour?

Answer 22

Tocolytics to allow time for steroids to be given to improve lung maturation.

Question 23

How much more common is pregnancy related hypertension in multiple pregnant women than singleton women?

Answer 23

3 times

Question 24

Why is pregnancy-induced hypertension so much more common in multiple pregnancy?

Answer 24

Larger size of the placental bed

Question 25

What is twin-to-twin syndrome?

Answer 25

Blood is shunted across fetal vascular anastomoses, such that the donor becomes anaemic and growth restricted, with oligohydramnios and the recipient becomes fluid overloaded with polyhydramnios.

Question 26

What is the incidence of twin-to-twin syndrome in monochorionic diamniotic twins?

Answer 26

15%

Question 27

When does twin-to-twin syndrome usually occur?

Answer 27

In the second trimester

Question 28

What is the risk of fetal death in untreated twin-to-twin syndrome?

Answer 28

80%

Question 29

What is the risk of handicap in the surviving twin in twin-to-twin syndrome?

Answer 29

10%

Question 30

How do we manage twin-to-twin syndrome?

Answer 30

Laser treatment to placental anastomoses (FLAP - fetoscopic laser ablation of the placenta) Amniodrainage may be appropriate at later gestation

Question 31

What are the complications of a scenario where one fetus of a set of monochorionic twins has died and how do we manage this?

Answer 31

Puts surviving twin at risk of neurological damage Puts mother at risk of DIC as thromboplastins are released into the circulation. Pregnancy can be managed conservatively until surviving twin reaches a gestation with improved likelihood of survival. 80% of surviving twins can be delivered vaginally

Question 32

How is the delivery of multiple pregnancy managed?

Answer 32

Neonatal unit intensive care facilities Allow vaginal delivery if normal pregnancy and twin 1 cephalic presentation IV access / FBC / G+S Regional anaesthesia - to allow for more manipulation Continuous CTG monitoring Fetal scalp electrode to twin 1 IV syntocinon infusion to start after delivery of twin 1 ECV can be used if twin 2 not in longitudinal presentation IV syntocinon infusion to continue for third stage to reduce PPH

Question 33

If twin 1 is not in cephalic presentation at labour, how is delivery of multiple pregnancy managed?

Answer 33

Normally c-section

Question 34

How do we manage higher order multiple pregnancies?

Answer 34

Nearly always c-section

Question 35

What is locked twins?

Answer 35

Rare complication of vaginal deliveries when first twin is in breech. Aftercoming head of twin 1 is prevented from entering pelvis by head of cephalic presenting twin 2.

Question 36

How do we manage locked twins?

Answer 36

If first stage of labour: c-section If second stage of labour: general anaesthesia to allow necessary manipulation

Question 37

What is selective fetocide and why is it done in higher order multiple pregnancies?

Answer 37

Intracardiac potassium chloride given to one or more fetuses under ultrasound guidance to improve outcome of remaining fetuses.

Question 38

When is selective fetocide usually performed?

Answer 38

11-14 weeks

Question 39

What is the procedure-related risk of miscarriage in selective fetocide?

Answer 39

6%