Multiple Pregnancy

Question 0

What is a dizygotic twin and how common are they?

Answer 0

A zygote resulting from the fertilisation of two different Oocytes by two different sperm

Two thirds of all multiple pregnancies

No more genetically similar than siblings

Question 1

How common are twins?

Answer 1

One in 80 pregnancies

Triplets are one in a 1000 pregnancies

Question 2

What is a monozygotic twin and how common are they?

Answer 2

Result of mitotic division of a single zygote into ‘identical’ twins

This occurs in 3.5 out of every 1000 births

Whether they share the same amnion or placenta depends on the time of their division

Question 3

If a zygote divides at day three or less, what do the twins share?

Answer 3

Dichorionic, diamniotic

So share nothing but genes!

Occurs in 30%

Scan every 4 weeks
Can have normal delivery if first is cephalic
Deliver by 37 weeks

Question 4

If a zygote divides at days 4-8, what do the twins share?

Answer 4

Mono chorionic, diamniotic

So share a placenta but keep their own amniotic sacs

Occurs in 70%

Scan every 2 weeks
Deliver by 36 weeks

Question 5

If a zygote divides at days 9-13, what do they share?

Answer 5

Mono chorionic, mono amniotic

This is very rare

Scan every 2 weeks
Deliver at 34 weeks
Refer to specialist tertiary centre

Question 6

What happens if a zygote divides later than day 14?

Answer 6

Conjoined twins

This is very rare indeed

Question 7

Do monochorionic twins have a higher or lower fetal loss rate than Dichorionic twins?

Answer 7

Higher, particularly before 24 weeks

Question 8

What risk factors increase the risk of multiple pregnancy?

Answer 8

Familial factors - apparent in dizygotic twinning, on maternal side only

Parity and maternal age- rates of multiple pregnancy increases with parity in dizygotic twins, and with maternal age

Ovulation induction - eg gonadotrophins

IVF - 20% are multiple

Question 9

What are the antepartum complications of multiple pregnancy?

Answer 9

Preterm labour-40% deliver <37 weeks

Miscarriage -resorption of a foetus is common in early gestation also, so incidence of partial miscarriage are also high

Pre-eclampsia and gestational diabetes

Intrauterine growth restriction - twins grow at same rate as singletons until 28 weeks, but thereafter growth is slower

Twin twin transfusion syndrome

Congenital abnormalities are 2-4x more common

Polyhydramnios - may cause PROM

Question 10

How are multiple pregnancies usually diagnosed?

Answer 10

Vomiting may be more marked in early pregnancy

Uterus is larger than expected from the dates and palpable before 12 weeks

Later in pregnancy, three or more foetal poles may be felt

Many diagnosed only at ultrasound

Question 11

What is twin-twin transfusion syndrome and how common is it?

Answer 11

10-15% of all monozygotic twin pregnancies

One foetus transfuses the other through interlinked vascular channels

Commonly presents between 14-24 weeks

Question 12

What happens to the donor twin in twin-twin transfusion syndrome?

Answer 12

Becomes oliguric and growth restricted with oligohydramnios

Question 13

What happens to the recipient twin in twin-twin transfusion syndrome?

Answer 13

Will display polycythaemia, cardiomegaly, Hydrops foetalis and polyhydramnios

Question 14

What is the treatment for twin twin transfusion syndrome?

Answer 14

Serial amnioreduction
Selective foeticide
Laser ablation of communicating vessels

Question 15

What are the intrapartum complications of twins?

Answer 15

Malpresentation if the first twin occurs in 20% - this is an indication for c-section

Foetal distress in labour is more common

Second twin is vulnerable to cord prolapse, uterine contraction or placental abruption

Postpartum haemorrhage is more common - 10%

Question 16

What is the Antepartum management of twins?

Answer 16

Consider high risk pregnancy

Iron and folic acid supplements

Selective reduction to a twin pregnancy at 12 weeks to those with triplets or more

Seek anomalies at the 20 week scan - perform scans every four weeks from 24/40

Question 17

What is the intrapartum management of multiple pregnancy?

Answer 17

Caesarean indicated when first twin is breech presentation or transverse lie (and other indications)

Otherwise, vaginal delivery

Induce at 38 weeks, and labour can be augmented with oxytocin

CTG advised as the risk of intrapartum hypoxia is increased, particularly for second twin

Monitor first twin with scalp electrode or abdo USS

Epidural may be necessary as second twin can be problematic

Question 18

What are the different ways twins may present at delivery, and how common are these?

Answer 18

Cephalic/cephalic - 50%

Cephalic/breech - 25%

Breech/cephalic - 10%

Breech/breech - 10%

Question 19

What are the indications for Caesarean section in multiple pregnancy?

Answer 19

Previous c-section scar
Long history of subfertility 
Severe pre-eclampsia or DM
Premature labour (28-34 weeks)
Malpresentation of first twins

Question 20

How is the second baby delivered?

Answer 20

Lie is checked and external cephalic version performed if lie is not longitudinal

CTG must continue

Oxytocin started as contractions may decrease

When head is in pelvis, membranes are ruptured and pushing begins again

Delivery is usually within twenty minutes