many beans Flashcards
what is the natural incidence of twins
1/80
what is Hellin’s Law
mathematical approximation of the natural incidence of higher order multiple pregnancies
x2 = 1/89
x3 = 1/89^2
x4 = 1/89^3
fertilization of a different ova at different times (different cycles) is called __
superfetation
aka superfecundation
sonographic feature of superfetation
twins with diff GA
*hard to differentiate from twins with IUGR
how to you confirm heteropaternal superfecundation
genetic testing
?after birth
fertilization of two ova is called
dizygotic (DZ)
a single fertilized ovum that splits into two is called
monozygotic (MZ)
dizygotic aka
fraternal
*non identical
which type of zygocity has an increased risk of anomalies
monozygotic
monozygotic aka
identical twins
inherited conditions seen in one MZ twin are __ in the other twin
likely also
how to definitively confirm prenatal zygocity
amniocentesis
chorionic villous sampling
cordocentesis
postnatal zygocity is confirmed by __
DNA fingerprinting
what is the incidence of multiples in general today
1.5%
what is the most common zygocity of triplets
2 fertilized ova (DZ) including one set of MZ
risk factors for DZ twin incidence
advanced mat age
ART
race (++Nigeria)
previous DZ twins
increased parity, height, obesity
ris
risk factors for MZ twins
conception within 1 y of ceasing to use oral contraceptives
- considered a random event due to same rate worldwide
chorionicity refers to the no. of __
placentas
*chorionic sacs
amniocity refers to no. of __
yolk sacs
*amniotic sacs
if MZ splits very early (0-4 d), becomes __
DCDA
*still MZ origin
if MZ splits 4-8 d becomes __
MCDA
if MZ splits >8 d becomes __
MCMA
if MZ splits >13 d becomes __
conjoined
what combination of chorionicity and amniocity is NOT possible
DCMA
what options of chorionicity is possible with DZ twins
ONLY DCDA
chorionicity and amniocity of MZ twins depends on __
timing of twinning
there are __ in the intertwin membrane of DCDA twins that are MZ
4
*fused but separate placentas
*twin peak sign
there are __ in the intertwin membrane of DCDA twins that are DZ
4
there are __ in the intertwin membrane of MCDA twins
2
there are __ in the intertwin membrane of MCMA twins
0
‘time’ in twinning refers to the no. of days after __ that the twins separate
fertilization
what percentage of MZ twins split between 4-8 days
67%
*MCDA
how do you differentiate a DZ from a MZ pregnancy if both present as DCDA
you cannot UNLESS later on you can demonstrate each fetus is of a different sex
what are the main complications of multiples pregnancy
preterm delivery
PROM
IUGR
complications of MCMA twins (5)
TTTS
acardiac twins
twin embolization
cord entanglement
conjoined
demise of one twin followed by the clotting in the surviving twins’ circulation is called __
twin embolization syndrome
TTTS is easier to recognize if __
MCDA
what is the most common twin presentation
cephalic with vertex presenting part (against internal OS)
clinical manifestation of multiples on labs in 1st trimester will show __ betas and MSAFP
high
twins have a __ mortality rate than singletons
higher
* especially in MZ
u/s is most accurate in identifying DCDA twins from __ GA
6-9 w GA
*++thick septum
you see 2 YS, 1 GS, 2 fetal poles and an amnion between each embryo - what is the ddx
MCDA
you see no amnion between 2 embryos at 8w GA, 1 YS and 2 fetal poles - what is the ddx
MCMA
* bros before amnios
you see 2 GS, with a YS and a fetal pole in each - what is the ddx
DCDA
presence of 2 YS without visualization of the amniotic membranes confirms DA - T/F
TRUE
*should prompt followup for confirmation
when one embryo dies and is resorbed while the other continues to grow this is called __
vanishing twin
cause of vanishing twin
often idiopathic
more common with chromosomal abnormalities
false appearance of a second GS called
pseudotwin
cause of pseudotwin pregnancy
SCH
artifact
visualization of 2 placentas reliably predicts __
DCDA
visualization of a single placenta reliably predicts monochorionicity
NO
could be dichorionic with two fused placentas
*can only be differentiated by membranes
twin peak sign is a sign of attachment with __ twins
DCDA fused placentas
T intersection at placental attachment of amnions indicates __
MCDA
a single placenta
a MZ pregnancy with DC can develop into different sexes - T/F
FALSE
identical twins regardless of chorionicity
if placental CI close together or entagled in 2nd, 3rd trimester - likely __ pregnancy
MA
*likely no separating membrane whatsoever
twin discordance represents a difference of 15% weight, of > __ weeks GA difference
> 2 w
if one placenta viewed at 2nd, third trimester - sonographer must try to document __
twin peak sign and location of placental CI
TTTS is a __ pregnancy complicated by a twin-twin connection of blood supplies in the placenta
monochorionic
anastomosis between donor artery and recipient vein is the __
infrafetal placental shunt
TTTS usually presents with __ pregnancies
MCDA
*two amniotic sacs
in TTTS, the donor twin is aka as the __
stuck twin
in TTTS, the donor twin often associated with
oligohydramnios
in TTTS, recipient twin is usually larger and at risk of __
strain on the heart (LGA)
polyhydramnios (increased urinary output)
hydrops
in TTTS, amniotic fluid discordance only seen if __
diamniotic
‘stuck twin’ sign aka
cocoon sign
TTTS with unequal passage of RBC via placental anastomoses is referred to as
twin anemia polycythemia sequence
TAPS
*dx via pulsed Doppler of MCAs
in twin anemia polycythemia sequence, the donor twin becomes __ while the recipient becomes __
donor becomes anemic
recipient becomes polycythemic
what does TAPS stand for
twin anemic polycythemia sequence
do you expect to see hydramnios issues or stuck twin with TAPS
no
*only indication is elevated PSV in donor MCA and decreased PSV in recipient MCA (higher resistance) from anastamosis
what are causes of TAPS
chronic TTTS from tiny, unidirectional anastomoses
secondary to TTTS laser ablation
what does TRAP sequence stand for
twin reversed arterial perfusion
when MC have one acardiac live fetus perfused by ‘pump’ twin - this is called
TRAP sequence
what is the most common physical deformity possible with TRAP sequence
acardiac twin demonstrating acardis-acephalus (no head no heart)
what causes imbalance of intrafetal circulation in TRAP sequence
placental artery-artery anastomoses within a shared placenta
TRAP secuence usually occurs with what sex of twins
female
in an acardiac twin with TRAP sequence, what waveform would you expect from the umbilical vein
reversed flow (toward placenta, away from fetus)
TRAP sequence blood flows __grade into acardiac twin via umbilical artery
retrograde into fetus
in acardiac TRAP sequence twin, there will be gradual loss of normal form and relative sparing of __ body
lower body
sonographic features of pump twin in TRAP sequence gestation
normal or increased AF
+/- hydrophic
sonographic features of acardiac twin in TRAP sequence gestation
absent/ rudamentary heart, head, upper limbs
hydrops
2VC
how many umbilical arteries in acardiac twin TRAP sequence
1
what is the most important aspect of scanning TRAP sequence
pulse the umbilical vessels of abnormal twin to prove reversed flow in umbilical artery
twin embryos develop but don’t fully separate is called
parasitic twin
parasitic twin aka
asymmetrical
unequal conjoined twin
what is the chorionicity and amniocity of unequal conjoined twins
can only be MCMA
term for situation where one fetus enveloped inside its twin
fetus in fetu
the fetus in fetu chorionicity/amniocity is usually
can ONLY be MCMA
the fetus in the host with a fetus in fetu situation demonstrates __
living organ system with torso and limbs
blood supply
no functional brain heart lungs GI or urinary tract
DZ twins usually have __ defects
non concordant
oligohydramnios resultant from __ anomaly
fetal GU tract anomaly
IUGR
polyhydramnios usually due to __ anomaly
neural tube defect
upper GI tract obstruction
fetal hydrops
when MC twins with demise of one twin and subsequent vascular injuries to surviving twin referred to as __
twin embolization syndrome
vascular injuries associated with twin embolization syndrome result from disseminated __ coagulation
intravascular
(excessive clotting)
porencephaly / schizencephaly are complications of __ syndrome
twin embolization syndrome
*abnormal cystic areas to brain w/ communication of lat ventricles
when one fetus dies and is pressed against the uterine wall by growth of surviving twin, this is called __
fetus papyraceous
aka fetus compressus, paper-doll fetus
incomplete division of obryonic disc by __ d after fertilization results in conjoined twins
> 13d
what sex is more commonly associated with conjoined twins
female
__ is when conjoined twins at the xiphoid
xiphopagus
__ is when conjoined twins at the umbilicus
omphalopagus
__ is when conjoined twins at the rump
ischiopagus
__ is when conjoined twins at the sacral spine
pygopagus
__ is when conjoined twins at the head
craniopagus
__ is when conjoined twins at the chest
thoracopagus
which is the most common attachment of conjoined twins
thoracopagus
3 or more fetuses in one or more chorionic sacs are referred to as
high order pregnancies
chance of survival __ with no. of fetuses
decreases
combination of an extra uterine and intra uterine pregnancy is called
heterotopic pregnancy
*usually associated with ART
multifetal pregnancy reduction aka
selective fetocide
