Module 13 : Multiple Gestation Complications Flashcards
how much higher mortality rate for twins than singleton
5-10 times higher
twinning rate
- higher earlier in pregnancy
+ one may die and reabsorbed in early pregnancy - ART and IVF increasing rate of twins
types of twins
- dizygotic
- monozygotic
dizygotic
- fraternal twins
- zygote = number of eggs
- not sharing anything
- have their own placenta and amniotic sac
- dichorionic diamniotic
- as similar as siblings
monozygotic
- identical twins
- one egg
- chance of splitting early and not sharing anything
- or splitting late and sharing anything
sharing rule
- less than babies share the better the outcome of survival
dizygotic twins
- 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
increasing chance of dizygotic twins
- maternal age \+ young ( < 15) \+ old (> 37) \+ parity (many children) - hereditary - racial background - pharmaceutical agents \+ clomide and pergonal
monozygotic twins
- 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
types of monozygotic twinning
- dichorionic diamniotic
- monochorionic diamniotic
- monochorionic monoamniotic
- conjoined twins
chorionic
placenta
dichorionic diamniotic twins
- 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
monochorionic diamniotic twins
- 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
monochorionic monoamniotic twins
- 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
conjoined twins
- incomplete division at embryonic disc stage
- occurs after day 13 post fertilization
- no separating of membranes
scanning placentas - what to look for
- 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
2 placentas
- 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
twin peak / lambda sign
- 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
t sign
- 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
distinguishing between monozygotic DI/DI twins and dyzygotic twins
- can only tell if there is a boy and a girl
+ this means a dizygotic twin pregnancy
clinical indication for twin scan
- strong family history
- large for gestational age
- increased maternal hCG
- two or more heart beats heard by doctor
protocol
- 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%)
demised twin
- 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
fetal reduction
- 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
what are 6 abnormal twinning variations
- conjoined twins
- TRAP syndrome
- fetus in fetu
- hydatidiform mole with coexisting twin
- heterotopic pregnancy
- superfetation
where are conjoined towns most commonly attached
- chest or abdomen
+ thoracopagus or omphalopagus
what is TRAP syndrome
- twin reversed atrial perfusion
- arterial» arterial or venous»_space; venous shunts IN PLACENTA
what is the other twin called in TRAP syndrome
- acardiac parabolic twin
- acardiac monster
in what type of twinning does TRAP syndrome only occur in
- monochorionic twinning
ultrasound appearance of TRAP syndrome
- lack of separating membrane
- inability to separate fetal parts
- more than three vessels in cord
- complex anomalies
what are the physical characteristics of the acardiac twin in TRAP syndrome
- either no heart or very abnormal
- no head/heart which prevents twin from surviving
- completely perfused by the other donor twin
- on lower limbs and trunk
what condition is the donor twin susceptible to have in TRAP syndrome
- high risk for developing hydrops due to high cardiac output resulting in cardiac failure
what is fetus in fetu
- parasitic twin within abdomen of its sibling
- looks like a teratoma
what is superfetation
- fertilization of 2 separate ova months apart
what are 5 complications with twins
- twin to twin transfusion (TTTS)
- twin embolization
- premature delivery
- congenital anomalies
- cord accidents
in what types of twins does TTTS occur
- monochorionic twins only
what is TTTS
- arteriovenous fistulas in the placenta
+ A-A or V-V or A-V
+ A-v the worse because of difference in pressure gradient
what will the physical characteristics be of the fetuses with TTTS
- anemic donor
- fluid overload recipient
+ getting fluid from placenta and donor
characteristics of recipient twin in TTTS
- larger
- hypertensive
- polyhydramnious
- edematous
characteristics of donor twin in TTTS
- small
- hypotensive
- oligohydramnious
- stuck twin appearance
ultrasound appearance of TTTS
- discrepancy in size > 20%
- disparity in amniotic fluid
- single placenta seen
- thin or no membrane seen
- hydrops of one twin
what is a stuck twin
- donor twin in TTTS may have little or no fluid
- amniotic membrane holds baby tightly to uterine wall
can stuck twin occur in dichorionic twinning
- yes with placenta insufficiency
when does twin embolization syndrome occur and with what type of twins
- demise of a twin
- monochorionic twins
what is twin embolization syndrome
- clots pass from demised twin to surviving twin causing infarcts in live fetal brain or liver
what can twin embolization syndrome cause
- sever hypotension in surviving twin due to demised twin placenta becoming a low pressure bed allowing blood to pool in placenta causing asphyxia
ultrasound appearance of twin embolization syndrome
- ventriculomegaly, porenchephalic cysts, cerebral atrophy, microcephaly
- papyraceous fetus
why does premature delivery occur with twins
- uterus unable to accomadate 2 fetuses to term
- cervix begins to shorten or efface
what is the risk of congenital anomalies in monozygotic and dizygotic twins
- more common in monozygotic than singleton
- dizygotic is same risk as singleton
what type fo twins have increased risk of cord accidents and what are examples of cord accidents
- mono mono twins
- tangle, prolapse, wrap around fetal neck and strangle
what is the usually waveform of the umbilical artery
- low resitance
- lots of diastolic flow
- S/D ratio = 2
- PI at 28 weeks = 11
what would be considered bad umbilical artery flow
- no diastolic flow
what would be super bad umbilical artery flow
- reverse diastolic flow
- PI = super high
what is normal ductus venosus waveform
- triphasic
- some aliasing
- no reversal
what do the parts of the ductus venosus waveform represent
- first peak ventricular systole
- second peak passive filling of ventricular diastole
- reversal A wave
what is an abnormal ductus venosus waveform and what does it represent
- increased reversal of A wave
- myocardial impairnment
- increased ventricular end diastolic pressure from increased right ventricular afterload
what is the normal waveform of the MCA and at what angle do we sample it
- high resistance
- 0º insonation on MCA closest to transducer
what would cause an abnormal MCA waveform and what would it look like
- vasodilation occurs with brain sparring IUGR
- PI reduces and increased diastolic flow
