Multiple Pregnancy

Question 1

whats the incidence of twin and triplet births in the UK

Answer 1

twins: 1 in 80

Triplet: 1 in 1000

Question 2

what are the two main types of twins

Answer 2

Dizygotic (2/3) and Monozygotic (1/3)

Question 3

what are differences between monozygotic and dizygotic twins

Answer 3

genetically dizygotic twins are no more related than siblings, but monozygotic twins are formed from the mitosis of a single zygote and are therefore ‘identical’

Question 4

whats the aetiology of multiple births

Answer 4

Assisted conception

Genetic factors

Increasing maternal age

Parity

Question 5

what are early features of multiple birth

Answer 5

more pronounced vomiting

uterus will be larger than expected for gestation and will be palpable <12 weeks

Question 6

what are the maternal complications with multiple birth

Answer 6

Obstetric complications are exaggerated with multiple pregnancy

Pre-eclampsia and gestational diabetes are more common

Anaemia is also more common, partly from the dilutional effect but also because more iron and folic acid is required

Question 7

what are the foetal complications with multiple births that affect all types

Answer 7

Higher mortality (6x twins)

Higher rates of handicap (5x twins, 18x triplets)

Miscarriage

A twin can go missing if in 1st trimester

Late miscarriage is also more common

Preterm labour

IUGR is more common

Congenital abnormalities

Malpresentation

Foetal distress

PPH

Question 8

what are complications unique to monochorionic pregnancies only

Answer 8

Twin-Twin transfusion syndrome

Twin anaemia polycythaemic sequence

Twin reversed Arterial perfusion

Co-twin death

Question 9

what is twin-twin transfusion syndrome and what kind of twin does it affect

Answer 9

unequal blood distribution in monochorionic-Diamniotic twins

recipient twin becomes fluid overloaded and develops massive polyhydramnios, cardiac failure

donor twin becomes volume depleted and develops IUGR, oligohydramnios and anaemia

Question 10

what is twin anaemia polycythaemic sequence (TAPS)

Answer 10

marked difference in Hb between twins but no change in liqor volume as seen in TTTS

Question 11

what is twin reversed arterial perfusion

Answer 11

Rare abnormality in MC twins

An abnormal, often acardiac twin is perfused by the other twin that acts as a pump

Severe risk of cardiac failure

Question 12

what is the risk to the other twin if one twin dies in utero

Answer 12

rapid drop in blood pressure causes transfusion from the other twin leading to severe hypovolaemia

30% of cases end in death/neurological damage

Question 13

what is the risk with monoamniotic twins

Answer 13

cords are always tangled

in utero death common

Question 14

what are the general management principles relating to ALL multiple births

Answer 14

Should be considered high risk pregnancy

Iron and folic acid given

Low dose aspirin advised also as there is a high risk of pre-eclampsia

MDT/specialist care advised by NICE

Question 15

how do you identify if twins are MC/DC

Answer 15

DC twins = dividing membranes is thicker as it meets the placenta (lambda sign)

MC twins = dividing membrane is thinner and perpendicular to the shared placenta (T sign)

Question 16

what are the surveillance principles for monochorionic twins

Answer 16

USS surveillance starts at 12 weeks, occurs every 2 weeks until 24 weeks and then 2-3 weeks after that

Question 17

how do you manage Twin-twin transfusion syndrome

Answer 17

laser ablation using USS and fetoscopy is preferred

if >24-26 weeks delivery

Question 18

what gestational period does twin-twin transfusion syndrome most commonly occur in

Answer 18

16-24 weeks

Question 19

how do you manage a high order (3+) pregnancy

Answer 19

Selective reduction to a twin pregnancy should be offered to a mother

Reduces the chance of preterm birth

Slightly higher early miscarriage rate as a result

Safest before 14 weeks

Surveillance afterwards is advised (based on chronocity), with delivery by 36 weeks

Question 20

what are the intrapartum management strategies for multiple births

Answer 20

Vaginal delivery if 1st twin is cephalic

37 weeks DC twins, 36 weeks MC twins

After this time perinatal mortality is increased

CTG monitoring advised – perinatal hypoxia risk increased, particularly in the 2nd twin

Epidural not required but helpful in difficult delivery

Contractions often diminish after the 1st twin, they do return but oxytocin may be used to induce contractions

Between births, the lie of the 2nd twin is checked and ECV performed if not longtitudinal

Excessive delay between the births of the twins is associated with worse outcomes, but so is excessive haste

Post-delivery a prophylactic oxytocin infusion is given to prevent post-partum haemorrhage

Question 21

when is a C-section indicated for delivery of multiple births

Answer 21

Antepartum complications

1st twin is breech or transverse

High order multiples

Question 22

if there are severe foetal abnormalities requiring termination, what methods are used at which gestational periods

Answer 22

Before 14 weeks, intracardiac injection of KCL is used for DC twins

May be offered up to 32 weeks if late termination is legal

For MC twins the cord must be occluded using bipolar dithermy or the insertion ablated as the circulation is shared