Multiples In Pregnancy Flashcards
1
Q
Twinning accounts for how many natural pregnancies?
A
1%
2
Q
Twinning accounts for how many of all pregnancies?
A
3%
3
Q
Twinning rate has increased since when? Why?
A
- 1980s
- LMA and ART
4
Q
Why is there increased stats of twinning in LMA?
A
Due to an increase in FSH concentration as women age
5
Q
Prenatal mortality for twinning is what in North America?
A
13- 14%
6
Q
How much more higher is the mortality rate for twins compared to singletons?
A
5-10 x
7
Q
Twinning mortality rate is higher initially in utero, what happens to the dead twin?
A
One twin may die in early pregnancy and be re-absorbed resulting in single tone pregnancy
8
Q
Early u/s show that a large a number pregnancies start off how?
A
As twins
9
Q
Why is there a loss in twins in utero? 3
A
- Spontaneous abortion
- Embryonic malformation
- Non viable pregnancy
10
Q
What is a dizygotic twin - fraternal? 2
A
- Zygote meaning number of eggs
- Di = 2 eggs
11
Q
What are monozygotic twins?
A
Identical
12
Q
Dizygotic twins account for how many of the twins rate?
A
70%
13
Q
How many births are dizygotic twins? (Ratio)
A
1/80 births
14
Q
Is dizygotic twins hereditary or acquired?
A
Hereditary on maternal side
15
Q
What happens with the fertilization of dizygotic twins?
A
Fertilization of two separate ova
16
Q
What is the genetic similarity of the two dizygotic twins?
A
Same as siblings
17
Q
What increases the rate for dizygotic twins? 3
A
- Young mother
- Late maternal age
- Parity (increased number increases incidence)
18
Q
What is the hereditary for dizygotic twins?
A
Maternal side
19
Q
What is the racial background of individuals often affected by dizygotic?
A
- Asian rates low
- African rates high
20
Q
What pharmaceutical agents increase frequency of dizygotic twins? 2
A
Clovis and pergonal
21
Q
Monozygotic twins account for what percentage of all twins?
A
30%
22
Q
How random is the occurrence rate of monozygotic twins?
A
Random
23
Q
What is the occurrence rate of monozygotic twins? (Ratio)
A
1/250 births
24
Q
How is the ovum of the monozyogtic twins fertilized?
A
A single fertilized ovum replicates during early development
25
What is the genetic relation of monozygotic twins?
The same
26
What is the mortality rate of monozyogtic twins compared to dizygotic twins?
2x higher
27
Congenital anomalies occur how many times more often, in terms of monozygotic vs singleton?
2-3 times more often
28
What does chorionicity mean?
The number of placenta
29
What is the most important predictor of pregnancy outcome in twins?
Chorionicity
30
When is chorionicity best determined? (weeks)
10-14 weeks
31
What are the two signs of chorionicity?
1. Lambda (twin peaks)
2. T sign
32
What does Lambda sign mean? 2
1. Dichorionic
2. 2 placentas
33
What does the T sign mean? 2
1. Monochorionic
2. 1 Shared placenta
34
What do we need to do when we look at the membranes and placenta? 3
1. Identify the number of placentas
2. Identify the presence or absence of a separating membrane
3. Identify the presence of a twin peak sign or T sign where the membrane meets the placenta
35
If chorionicity cannot be determined transabdominally, what needs to be done?
EV scan is recommended
36
What sign is seen with DC/DA?
Twin peaks sign where membrane meets placenta
37
What sign is seen with MC/DA? (in terms of the sign and the placenta)
T sign where membrane meets the placenta
38
What membrane is seen with MC/MA?
No membrane
39
How many placentas are seen with DC/DA ?
2 Placentas, may appear separate or fused
40
How many placentas are seen with MC/DA?
1 Placenta
41
How many placentas are seen with MC/MA
1 placenta
42
What is the membrane like for DC/DA?
Thick membrane
43
What does the membrane look like for MC/DA?
Thin membrane
44
With dizygotic twins there will always be how many placentas?
2
45
If 2 placentas implant close together, what may happen?
They can fuse together
46
Some placental tissue may group up where? (In terms of fused placentas)
Between the membranes
47
What is the twin peak sign or lambda sign?
When some placental tissue grows up between the membranes
48
How does monochorionic/ diamniotic occur? What is a sign?
1. If twinning or division occurs after implantation, only one placenta is formed.
2. The membrane between the babies create a T sign
49
What re the different types of monozygotic twinning? 4
1. Dichorionic- diamniotic (Di/DI)
2. Monochorionic- diamniotic (Mono/Di)
3. Monochorionic- monoamniotic (mono/ mono)
4. Conjoined twins
50
Dichrionic- diamniotic twins occur with how many of dizygotic twins?
All cases
51
What is Di/DI?
Two placentas/ two amniotic sacs
52
Can Di/Di occur with monozygotic twins (one ovum)?
Yes
53
How can Di/Di happen with monozygotic twins? 3
1. Morula splits before it implants
2. 2 Days post fertilization
3. Each implant separately
54
How many monozygotic twins are di/di?
18-30%
55
What are complications of di/di?
Increased risk of preterm delivery
56
Monochorionic- diamniotic can be shortened to what abbreviation?
Mono/di
57
When does division occur with Mono/di?
At blastocyst stage, after the inner cell mass of the embryo forms
58
When does Mono/di occur?
Day 4-8 post fertilization
59
What is a Mono/Di pregnancy?
2 fetuses in separate amniotic sacs with a single chorionic sac. (1 placenta)
60
How many of all monozygotic twins are mono/di?
70%
61
What are complications of mono/ di?
Vascular distribution due to shared placenta
62
When does mono/mono occur? 2
1. At embryonic disc stage after the amniotic sac has formed
2. Day 8-12 post fertilization
63
What is mono/mono?
No membrane between fetuses, one placenta
64
How many monozygotic twins are mono/mono?
4%
65
What is the complications associated with mono/mono?
Increased risk of mortality due to cord entanglement
66
What is the chorion and amniotic sac for conjoined twins?
Mono-mono
67
When does incomplete division occur with conjoined twins?
At embryonic disc stage
68
When does conjoined twins occur?
Day 13 post fertilization
69
Is there a membrane with conjoined twins?
No
70
What is the sonographic protocol for twins? 4
1. Identify the number of fetuses present
2. Identify the position of both fetuses
3. Label the presenting twin (closest to the cervix) as A and label which side of the mom (uterus) this baby is on (left or right)
4. Identify chorionicity/ amnionicity by presence of membrane, # of placentas, Presence of twin peak sign or T sign
71
For better consistency in monitoring to reduce confusion, rather than labelling twins A/B at each scan based on proximity to cervix, it is now recommended to assign each individual twin as what?
Fetus 1 and fetus 2
72
Identifying features of each fetus are what? 8
1. Presentation
2. Presenting/trailing
3. Left/ right side
4. Gender
5. Larger, smaller
6. Placental position/ cord insertion
7. Markers
8. Structural abnormalities
73
What do we need to do with each fetus during protocol?
Scan each fetus as a singleton and complete all documentation before moving to the next fetus
74
What do we need to do with biometry measurements for twins?
Enter biometry measurements into separate calculation packages (fetus a/b)
75
What do we need to show to demonstrate multiple fetuses and compare size? 2
1. Head
2. Abdomen
76
What do we need to do with sonographic protocol? 2
1. Rule out polyhydraminos
2. Rule out fetal demise (papyraceus fetus)
77
What are 2 abnormal twinning variation?
1. Conjoined twins
2. TRAP syndrome
78
Conjoined twins are most commonly joined where? What is the occurrence rate?
1. At the chest or abdomen (thorocopagus or omphalopagus)
2. 70%
79
70% of conjoined twins are which gender?
Female
80
How many conjoined twins are still born?
1/3
81
How many conjoined twins die on day one of life?
1/3
82
What is the sonographic appearance of conjoined twins? 4
1. Lack a separate membrane
2. Inability to separate fetal parts
3. More than 3 vessels in the cord
4. Complex anomalies
83
What is diprosopus?
Duplication of anatomy seen in conjoined twins
84
What are examples of diprosopus?
Duplication of face or head
85
What is TRAP sequence? (acronym breakdown)
Twin reversed arterial perfusion
86
What is TRAP sequence also called?
A cardiac parabolic twin or a cardiac monster
87
TRAP sequence happen with what individuals?
Twins
88
TRAP sequence results from what?
Large arterial venous anastomosis (shunts) in the placenta
89
What is the blood flow seen with TRAP sequence with doppler? 3
1. Reversal of normal blood flow for the acardiac twin
2. Flow towards it in the umbilical arteries
3. Flow away from it in the umbilical vein
90
What is seen with TRAP sequence?
Either no heart (acardiac) or a very abnormal heart in one twin
91
What prevents TRAP twin from surviving on its own?
No head/heart
92
A TRAP sequence twin is perfused how?
Completely perfused by the other donor twin
93
What does the TRAP sequence baby develop?
Only the lower limbs and trunk
94
The donor twin in TRAP is at high risk for what?
Developing hydrops due to high cardiac output resulting in cardiac failure
95
What is fetus in fetu? How easy is this to identify? 2
1. A parasitic twin within abdomen of its sibling
2. Difficult to distinguish from a teratoma
96
What is an identifying factor of the coexisting twin for fetus in fetu?
Hydatidiform mole
97
What kind of pregnancy is fetus in fetu?
Heterotopic pregnancy
98
What is superfetation? How common is it? Who is affected?
1. Fertilization of two separate ova months apart
2. Extremely rare
3. Women undergoing fertility treatments
99
What is Twin to twin transfusion syndrome abbreviated to?
TTTS
100
What are 5 complications with twins?
1. TTTS
2. Twin embolization syndrome
3. Premature delivery
4. Congenital anomalies
5. Cord accidents
101
TTTS occurs with what kind of twins?
Monochorionic twins
102
TTTS affects what percentage of MC twins?
10-15%
103
What is seen with TTTS in the placenta?
Arteriovenous fistulas in the placenta
104
In terms of TTTS what does AV fistulas look like in placenta? Which is worse?
1. A-A or V-V or A-V
2. A-V is the worse because of difference in pressure gradient
105
What happens to the donor with TTTS?
Anemic donor and fluid overload
106
What is the mortality rate for TTTS?
70-80%
107
What is seen with stuck twin? (TTTs)2
1. Donor twin may have little or no flood
2. Amniotic membrane holds baby tightly to uterine wall
108
Stuck twin can occur in ___________ twin pregnancy as well where in one twin has what? 2
1. Dichorionic
2. One has Placenta insufficiency (IUGR) and the other twin as normal growth
109
What is the sonographic appearance of stuck twin? 4
1. Disparity in amniotic fluid
2. Single placenta/ Monochorionic
3. Thin or no membrane seen
4. Hydrops of one twin
110
What is the discrepancy in size for Stuck babies?
>20%
111
How many stages are there in TTTS?
5
112
What this the sonographic appearance of TTTS during stage 1?
Oligohydraminos in donor/ polyhydraminos in recipient due to unequal blood flow
113
What is the sonographic appearance of TTTS during stage 2?
Bladder not visualized in donor, due to blood being diverted to vital organs
114
What is the sonographic appearance of TTTS during stage 3?
Doppler signals abnormal
115
What does abnormal doppler signals mean with TTTS? 4
1. The heart function of one or both twins is affected
2. DV: reversed flow
3. Absent/ reversed diastolic flow
4. MCA: Low resistance (PI)
116
What kind of growth is seen with TTTS?
Discordant growth
117
What is the sonographic appearance of TTTS during stage 4?
Hydropic recipient twin
118
What is the sonographic appearance of TTTS during stage 5?
One or both fetal demise
119
With TTTS can polyhydraminos occur?
Yes with one twin
120
How do you do an AFI on a twin pregnancy?
1. Measure deepest vertical pocket (DVP), ideally in view of the dividing membrane
2. Oligohydraminos is <2cm,
3. Polyhydraminos is >8cm
121
What is doppler used for with TTTS?
Performed to assess blood flow to each fetus
122
What vessels are sampled for TTTS? 3
1. Umbilical artery (low resistance)
2. Middle cerebral artery (high resistance)
3. Ductus venosus (triphasic)
123
What is the preferred measurment for TTTS?
PI
124
TTTS doppler demonstrating no diastolic flow or reverse diastolic flow can be expressed with what?
PI?
125
How do we calculate PI?
A-B/mean
126
What is normal fetal doppler of the umbilical artery? 3
1. Lots of diastolic flow
2. S/D ratio = 2
3. PI at 28 weeks = 1
127
What is bad in terms of fetal doppler of the umbilical artery?
No diastolic flow
128
What is abysmal fetal doppler of the umbilical artery?
1. Reverse diastolic flow
2. PI of 6.02
129
How do we get a doppler of the ductus venosus?
From the AC locate the ductus by following the umbilical vein posterior towards the IVC
130
Aliasing when looking at doppler of the ductus venosus means what?
High velocity flow in the ductus venosus
131
What is seen with abnormal ductus venosus? 2 (Think peaks)
1. First peak corresponds to ventricular systole
2. Second peak corresponds with passive filling of the ventricular diastole
132
What does Abnormal ductus venosus look like?
Reversal of the A wave
133
Abnormal waveforms of the abnormal ductus venosus represent what/
Myocardial impairment and increased ventricular end-diastolic pressure from an increased in the right ventricle afterload
134
What does MCA stand for?
Middle cerebral artery
135
Where do we sample the MCA for doppler?
MCA closest to the transducer
136
What angle do we need fro MCA doppler?
0 degrees
137
In terms of MCA doppler, vasodilation occurs with what?
Brain sparing IUGR
138
What is the PI for MCA doppler? What about the Diastolic flow?
1. PI reduces
2. Diastolic flow increases
139
Twin embolization occurs when?
There is a demise of a twin in monochorionic twins
140
What can happen with twin embolization syndrome causing infarcts to the fetal brain or liver?
Clots can pass from demised twin to surviving twin causing infarcts in fetal brain or liver
141
Twin emboliztion syndrome may cause severe hypetention to the suriving twin, why?
Due to demised twin’s placenta becoming a low pressure bed allowing blood to pool in this placenta
142
What does twin embolization syndrome cause to the suriving twin?
Asphyxia (low oxygen) in the live surviving twin
143
What is the sonographic appearance of twin embolization syndrome? 4
1. Ventriculomegaly
2. Porencephalic cysts
3. Cerebral atrophy or Microcephaly
4. Demise of co-twin in DI/DI twin can result in a parlay race out fetus (bones remains)
144
Why does premature delivery happen?
Uterus is unable to accommoadate 2 fetuses to term
145
What happens to the cervix during premature delivery?
It shortens
146
To look out for premature delivery, what must be done with all twin pregnancies fetal assessments visits?
An EV measurement of the cervix until 32 weeks gestation
147
Genetic developmental abnormalities are more common in what kind of twin?
Monozygotic twin
148
In terms of monozygotic twins, how more higher is the incident rate for congenital anomalies?
2-3 times
149
What types of twins have the same risk of congenital anomalies as singletons?
Dizygotic twins
150
What kind of twin has cord entanglement pretty much all the time?
In MC/MA twins
151
What does cord accidents increase the risk of?
Cord accidents
152
What are examples of cord accidents? 3
1. May tangle
2. Prolapse
3. Strangle
