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Ob/Gyne > Module 9.1 : Multiple Gestation > Flashcards

Module 9.1 : Multiple Gestation Flashcards

1
Q

what percentage of natural pregnancies are twins

A

3%

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2
Q

how much higher mortality rate for twins than singleton

A

5-10 times higher

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3
Q

twinning rate

A
  • higher earlier in pregnancy
    + one may die and reabsorbed in early pregnancy
  • ART and IVF increasing rate of twins
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4
Q

types of twins

A
  • dizygotic

- monozygotic

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5
Q

dizygotic

A
  • fraternal twins
  • zygote = number of eggs
  • not sharing anything
  • have their own placenta and amniotic sac
  • dichorionic diamniotic
  • as similar as siblings
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6
Q

monozygotic

A
  • identical twins
  • one egg
  • chance of splitting early and not sharing anything
  • or splitting late and sharing anything
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7
Q

sharing rule

A
  • less than babies share the better the outcome of survival
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8
Q

dizygotic twins

A
  • 70% of all natural births
  • 1/80 births
  • hereditary on maternal side
  • fertilization of two separate ova
  • genetic similarity sam as siblings
  • have their own genetic mix
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9
Q

increasing chance of dizygotic twins

A 
- maternal age
   \+ young ( < 15)
   \+ old (> 37)
   \+ parity (many children)
- hereditary 
- racial background
- pharmaceutical agents
   \+ clomide and pergonal
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10
Q

monozygotic twins

A
  • 30% of all natural twins
  • 1/250 births
  • random occurrence
  • SINGLE fertilized ovum replicates during the early development
  • genetically the same
  • increased mortality rate is slightly higher than dizygotic twins
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11
Q

types of monozygotic twinning

A
  • dichorionic diamniotic
  • monochorionic diamniotic
  • monochorionic monoamniotic
  • conjoined twins
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12
Q

chorionic

A
  • placenta
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13
Q

dichorionic diamniotic twins

A 
- occurs with ALL dizygotic twins
   \+ two placentas two amniotic sacs
- can occur in monozygotic twins 
   \+ morula splits before it implants
   \+ 2 days post fertilization 
   \+ each implants separately (2 of everything, 4 layer membrane)
- 18-30% of all monozygotic twins
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14
Q

monochorionic diamniotic twins

A
  • division occurs at blastocyst stage after inner cell mass of embryo forms
  • day 4-8 post fertilization
  • 2 fetuses in separate amniotic sacs with single placenta
  • 2 layer membrane 1 placenta
  • 70% of all monozygotic twins
  • possibility of twin to twin transfusion
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15
Q

monochorionic monoamniotic twins

A
  • division occurs at embryonic disc stage after amnion’s sac develops
  • day 8-12 post fertilization
  • 4% of all monozygotic twins (rare)
  • increased risk of mortality due to cord entanglement
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16
Q

conjoined twins

A
  • incomplete division at embryonic disc stage
  • occurs after day 13 post fertilization
  • no separating of membranes
17
Q

scanning placentas - what to look for

A
  • identify number of placentas
  • identify presence or absence of a separating membrane
  • identify presence of a peak sign or t sign where the membrane meets the placenta
18
Q

2 placentas

A
  • with dizygotic twins or di chorionic twins there will be 2 separate placentas
  • or 2 placentas so close there appear fused looking like one placenta
  • look for lambda or t sign
19
Q

twin peak / lambda sign

A
  • if 2 placentas implant close together some placenta tissue will grow up between the membranes creating a twin peak sign or lambda sign
  • TWO PLACENTAS
20
Q

t sign

A
  • division occurring after implantation will result in one placenta
  • one placenta with two membranes creates a t sign
  • no placenta will grow between the membranes
  • monochorionic diamniotic
21
Q

distinguishing between monozygotic DI/DI twins and dyzygotic twins

A
  • can only tell if there is a boy and a girl

+ this means a dizygotic twin pregnancy

22
Q

clinical indication for twin scan

A
  • strong family history
  • large for gestational age
  • increased maternal hCG
  • two or more heart beats heard by doctor
23
Q

protocol

A
  • identify number of fetuses
  • position of fetuses
  • label presenting twin (closest to cervix) as A and label which side of the mom uterus baby is on
  • identify presence of
    + membrane
    + number of placentas
    + presence of twin peak sign or t sign
  • treat each fetus as a singleton and complete all documentation of one twin before moving on to the next
  • show similar fetal parts to demonstrate multiple babies
  • rule out polyhydroamnios (5-10%)
24
Q

demised twin

A
  • usually occurs in first trimester but can happen any time
  • if this happens the boney remains of the demised fetus is termed PAPYRACEUS FETUS
  • imaging of dead fetus only requires sag and trans image
25
Q

fetal reduction

A
  • increased rate of higher order multiples due to increased use of fertility treatment either with fertility drugs or IVF
  • much higher rate of prematurity
  • option is offered to have a fetal reduction (fetoscide) to improve outcome of pregnancy
26
Q

AFI on twin pregnancy

A
  • can’t do a real AFI

- try to locate a 2x2 pocket of fluid anterior to each baby as close to membrane as you can

Ob/Gyne (24 decks)

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