Module 9.1 : Multiple Gestation Flashcards
1
Q
what percentage of natural pregnancies are twins
A
3%
2
Q
how much higher mortality rate for twins than singleton
A
5-10 times higher
3
Q
twinning rate
A
- higher earlier in pregnancy
+ one may die and reabsorbed in early pregnancy - ART and IVF increasing rate of twins
4
Q
types of twins
A
- dizygotic
- monozygotic
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
6
Q
monozygotic
A
- identical twins
- one egg
- chance of splitting early and not sharing anything
- or splitting late and sharing anything
7
Q
sharing rule
A
- less than babies share the better the outcome of survival
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
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
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
11
Q
types of monozygotic twinning
A
- dichorionic diamniotic
- monochorionic diamniotic
- monochorionic monoamniotic
- conjoined twins
12
Q
chorionic
A
- placenta
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
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
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
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
