Intra/post - Multiple pregnancy

Question 1

what % of all pregnancies are twins

Answer 1

2% - (30% of those are identical)

Question 2

compared to single pregnancies, how does twin perinatal mortality compare (+why?)

Answer 2

perinatal mortality is 5x higher

due to increased incidence of prematurity and congenital abnormalities

Question 3

what is a zygote

Answer 3

a fertilised egg

Question 4

how long does it take for a blastocyst to develop

Answer 4

12 days to develop from a zygote to an embryo, then a morula then a blastocyst

Question 5

how long does it take before the blastocyst implants

Answer 5

14 days

Question 6

what are monozygotic twins

Answer 6

identical twins from one egg and one sperm - once fertilised the cell divides

Question 7

what are dizygotic twins

Answer 7

fraternal twins from two sperms and two eggs

Question 8

what is the chorion

Answer 8

foetal portion of the placenta - provides nutrition

Question 9

what is the amnion

Answer 9

innermost membrane that encloses the embryo - provides warmth and protection

Question 10

explain the term dichorionic

Answer 10

each twin has their own placenta/chorion

Question 11

explain the term monochorionic

Answer 11

twins that share a placenta/chorion

Question 12

explain the term diamniotic

Answer 12

each twin has their own amniotic sac

Question 13

explain the term monoamniotic

Answer 13

twins share an amniotic sac

Question 14

what can determine how independent the twins are of each other in the womb

Answer 14

the earlier the split of the amnion and chorion
e.g. the sooner after fertilisation the cells split, the more likely they are to develop separate amnions and chorions = better outcomes and more independence

Question 15

what will most likely result from cleavage of the morula during days 1-3

Answer 15

cleavage of the morula = dichorionic/diamniotic twins

Question 16

what will most likely result from cleavage of the blastocyst during days 4-8

Answer 16

cleavage of the blastocyst monochorionic/diamniotic twins

Question 17

what will most likely result from cleavage of the implanted blastocyst during days 8-13

Answer 17

cleavage of the implanted blastocyst = monochorionic/monoamniotic

Question 18

what will most likely result from cleavage of a formed embryonic disc during days 13-15

Answer 18

cleavage of formed embryonic disc = conjoined twins

Question 19

when is DCDA most commonly seen

Answer 19

in dizygotic twins

Question 20

when is MCDA most commonly seen

Answer 20

in monozygotic twins

Question 21

when would DCDA be seen in monozygotic twins

Answer 21

if the split of the cells is very early i.e. before develops into a blastocyst

Question 22

when is MCMA most commonly seen

Answer 22

rarest of the three combinations - but only seen in monozygotic twins

Question 23

which of DCDA, MCDA and MCMA is most risky and why

Answer 23

MCMA - due to placental insufficiency and cord entanglement

Question 24

what can increase mortality in monochorionic twin pregnancies

Answer 24

preterm labour
congenital abnormalities 
growth restriction
placental insufficiency
twin-twin transfusion syndrome
malpresentation
4x increased risk of death due to hypoxia for the second twin

Question 25

when are DCDA twins most commonly delivered

Answer 25

37-38 weeks

Question 26

when are MCDA twins most commonly delivered

Answer 26

36-37 weeks

Question 27

when are MCMA twins most commonly delivered

Answer 27

32-34 weeks

Question 28

what might determine if a mother has a c-section vs vaginal delivery with twins

Answer 28

complications
previous deliveries
presentation/lie of twins

Question 29

what procedures/provisions are commonly needed to assist twin deliveries

Answer 29

theatre available 
CTG monitoring 
cord clamping 
scan 2nd twin for presentation
stabalise lie/ECV
oxytocin
vaginal assisted/c-section available