9.1: Normal Multiple Gestations

Question 1

twins should be b/w what growth percentile of each other?

Answer 1

~20%

Question 2

are twin pregnancies automatically high risk

Answer 2

yes

Question 3

mortality rate of twins compared to single babies

Answer 3

5-10 X higher

Question 4

why are the number of twins initially higher in early preg

Answer 4

often one twin will die in early preg leaving 1 baby… many pregnancies start as twins

Question 5

what are the 2 main types of twins? and how many eggs do they include

Answer 5

• dizygotic (fraternal): 2 eggs, so genetically different

- monozygotic (identical): 1 egg that splits, so genetically identical

Question 6

are dizygotic twins hereditary?

Answer 6

yes, on the maternal side

Question 7

what maternal age is associated w/ increased chances of having dizygotic twins

Answer 7

• young (15)

- advanced maternal age >37

Question 8

what are the factors thats increase the chances of having dizygotic twins

Answer 8

• young
• advanced maternal age >37
• hereditary
• racial background
• pharmaceutical agents (clomide and pergonal… fertility drugs that increase ovulation)

Question 9

which racial background has the lowest incidences of dizygotic twins? highest incidence?

Answer 9

lowest: Japanese
Highest: Nigerian

Question 10

are monozygotic twins hereditary?

what determines the number of membrane in a monozygotic preg

Answer 10

no, random occurrence

when the egg splits

Question 11

what type of twins have a higher mortality rate (dizygotic or monozygotic)?

Answer 11

monozygotic because they can share more structures

Question 12

anytime twins share a placenta theres a risk of what event occurring?

Answer 12

twin to twin transfusion which occurs when the vessels in the placenta anastomse

Question 13

what are the 4 types of monozygotic twins

Answer 13

• dichorionic/diamniotic
• monochorionic/diamniotic
• monochorionic/monoamniotic
• conjoined

Question 14

are all dizygotic twins DI/DI

Answer 14

yes

Question 15

when will monozygotic twins be DI/DI

how many membranes and placentas in this type of twin preg

Answer 15

• if the morula splits before it implants (~ 2 days post fertilization)
• each egg implants separately
• 4 membranes (we dont see these membranes after 16 wks becasue the chorion and amnion fuse at 16 wks)
• 2 placentas

Question 16

whats the only way we can tell monozygotic DI/DI twins from dizygotic DI/DI twins?

Answer 16

only if theres a dizygotic DI/DI preg w/ one girl and one boy

Question 17

when will monozygotic twins be Mono/DI

how many membranes and placentas in this type of twin preg

Answer 17

-if division of the egg occurs at the blastocyst stage after the inner cell mass of the embryo forms and implantation has occurred (~ 4-8 days post fertilization)

• 2 membranes
• 1 placenta

Question 18

when will monozygotic twins be Mono/Mono

how many membranes and placentas in this type of twin preg

Answer 18

• when the division of the egg occurs after the embryonic disc stage, after the amniotic sac has formed (~ 8-12 days post fertilization)
• 1 membrane (No membranes b/w the fetus)
• 1 placenta

Question 19

why do monozygotic Mono/Mono twins have a higher mortality rate

Answer 19

due to cord entanglement

Question 20

when will monozygotic twins be conjoined

how many membranes in this type of twin preg

Answer 20

• when there incomplete division at the embryonic disc stage (division is after 13 days post fertilization)
• no separating membranes

Question 21

what is a fused placenta

what sign will this create and why?

Answer 21

• when the 2 placentas of the DI/DI preg implant so close together that they appear fused
• creates the Lambda sign or ‘twin peak sign’ because some of the placenta grows up b/w the membranes

Question 22

what sign will a Mono/DI preg show on US

Answer 22

T- sign

Question 23

what are the clinical indications for a scan for twin preg

Answer 23

• strong family history
• LGA
• high maternal hCG levels (b/c of 2 placentas)
• 2 or more heart beats heard by doctor
• severe morning sickness due to increased hCG

Question 24

which twin would we label twin A?

what else would we include in our labeling of the twins?

Answer 24

• the baby thats closet to the cervix or the ‘presenting twin’
• would also include which side of mom each twin is on

Question 25

do you complete all documentation of 1 twin before moving on to the next

Answer 25

yes

Question 26

what type of image is often taken to prove that there are 2 babies

Answer 26

-an images that shows similar fetal parts close together

Question 27

its important to rule out what condition rated to amniotic fluid levels when assessing the twins

Answer 27

polyhydramnioses

Question 28

when does a fetal demise of one twin often occur

Answer 28

during 1st trimester preg... but can occur at any time

Question 29

what is a papyraceus fetus | how do we document it

Answer 29

- the boney reminds of a demised fetus | - 1 SAG and 1 TRANS image

Question 30

what is the term that refers to a fetal reduction and why would it be performed

Answer 30

- fetoscide | - in high number multiple preg to reduce the risk of preterm labour and improve the outcome of the preg

Question 31

can we do an AFI on a twin preg? what amount of amniotic fluid do we look for

Answer 31

no.... try to see a pocket of fluid of at least 2X2 near the membrane or around the fetuses