9.1: Normal Multiple Gestations Flashcards
twins should be b/w what growth percentile of each other?
~20%
are twin pregnancies automatically high risk
yes
mortality rate of twins compared to single babies
5-10 X higher
why are the number of twins initially higher in early preg
often one twin will die in early preg leaving 1 baby… many pregnancies start as twins
what are the 2 main types of twins? and how many eggs do they include
- dizygotic (fraternal): 2 eggs, so genetically different
- monozygotic (identical): 1 egg that splits, so genetically identical
are dizygotic twins hereditary?
yes, on the maternal side
what maternal age is associated w/ increased chances of having dizygotic twins
- young (15)
- advanced maternal age >37
what are the factors thats increase the chances of having dizygotic twins
- young
- advanced maternal age >37
- hereditary
- racial background
- pharmaceutical agents (clomide and pergonal… fertility drugs that increase ovulation)
which racial background has the lowest incidences of dizygotic twins? highest incidence?
lowest: Japanese
Highest: Nigerian
are monozygotic twins hereditary?
what determines the number of membrane in a monozygotic preg
no, random occurrence
when the egg splits
what type of twins have a higher mortality rate (dizygotic or monozygotic)?
monozygotic because they can share more structures
anytime twins share a placenta theres a risk of what event occurring?
twin to twin transfusion which occurs when the vessels in the placenta anastomse
what are the 4 types of monozygotic twins
- dichorionic/diamniotic
- monochorionic/diamniotic
- monochorionic/monoamniotic
- conjoined
are all dizygotic twins DI/DI
yes
when will monozygotic twins be DI/DI
how many membranes and placentas in this type of twin preg
- 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
whats the only way we can tell monozygotic DI/DI twins from dizygotic DI/DI twins?
only if theres a dizygotic DI/DI preg w/ one girl and one boy
when will monozygotic twins be Mono/DI
how many membranes and placentas in this type of twin preg
-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
when will monozygotic twins be Mono/Mono
how many membranes and placentas in this type of twin preg
- 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
why do monozygotic Mono/Mono twins have a higher mortality rate
due to cord entanglement
when will monozygotic twins be conjoined
how many membranes in this type of twin preg
- when there incomplete division at the embryonic disc stage (division is after 13 days post fertilization)
- no separating membranes
what is a fused placenta
what sign will this create and why?
- 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
what sign will a Mono/DI preg show on US
T- sign
what are the clinical indications for a scan for twin preg
- 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
which twin would we label twin A?
what else would we include in our labeling of the twins?
- the baby thats closet to the cervix or the ‘presenting twin’
- would also include which side of mom each twin is on
do you complete all documentation of 1 twin before moving on to the next
yes
what type of image is often taken to prove that there are 2 babies
-an images that shows similar fetal parts close together
its important to rule out what condition rated to amniotic fluid levels when assessing the twins
polyhydramnioses
when does a fetal demise of one twin often occur
during 1st trimester preg… but can occur at any time
what is a papyraceus fetus
how do we document it
- the boney reminds of a demised fetus
- 1 SAG and 1 TRANS image
what is the term that refers to a fetal reduction and why would it be performed
- fetoscide
- in high number multiple preg to reduce the risk of preterm labour and improve the outcome of the preg
can we do an AFI on a twin preg?
what amount of amniotic fluid do we look for
no…. try to see a pocket of fluid of at least 2X2 near the membrane or around the fetuses
