multiples- test 4 Flashcards
T/F
There is a greater danger when twins share a single placenta or single sac
True
2 types of twins
Monozygotic
Dizygotic
what is zygosity
Number of oocytes released from ovary and fertilized by spermatazoa
When should you determine zygosity?
Should only be determined > 6 wks GA
what is “vanishing twin” phenomenon.
one twin may die and is expelled or absorbed by mother
what is Chorionicity?
Number of chorionic sacs (placentas)
when is chorionicity determined
Assessed > 4.5-5 wks
can two placentas appear as one?
yes.
what is amnionicity
Number of Amniotic sacs
when is amnionicity determined?
Assessed > 8 wks GA
Best identified in 1st trimester
The process of twinning is diagrammed here. A dividing membrane that is “monochorionic” implies monozygous twinning.
However, a “dichorionic” twin placenta could result from either dizygous or monozygous twinning (the former more likely)
diamniotic
monochorionic
dichorionic
diamniotic
how many chorion and amnions does Dizygotic Twins havw
ALWAYS dichorionic and diamniotic
One blastocyst which divides, producing two embryos
Monozygotic Twins (30%)
Majority of monozygotic twins are _____________, _____________
monochorionic, diamniotic
Monozygotic Twins
Cleavage at the 2-cell stage (days 1-3) results in _______________, _____________
dichorionic-diamniotic (di-di),
DCDA gestation; 20 % of MZ twin pregnancies.
Monozygotic Twins
Cleavage during the blastocyst stage, before implantation (days 4-8) results in _____________, ______________
monochorionic-diamniotic (mono-di),
MCDA gestation; 75% of MZ twin pregnancies.
Monozygotic Twins
Cleavage after implantation results in ______________, ______________
monochorionic-monoamniotic (mono-mono),
MCMA gestation (days 8-13); 5% of MZ twin pregnancies.
Monozygotic Twins
Division > 2 weeks results in _______________: <1% of MZ twin pregnancies.
conjoined twins
dichorionic vs monochorionic thickness
dichorionic
>2mm
4 layers (amnion-chorion-chorion-amnion)
Monochorionic
< 2 mm
2 layers
(amnion-amnion)
what is another way to tell the difference between dichorionic or monochorionic besides thickness
Dichorionic
“twin-peak”/lambda sign
Monochorionic
T-shaped junction
dichorionic
diamniotic
monochorionic
monoamniotic
dichorionic
diamniotic
monochorionic
diamniotic
The successful fertilization of a second ovum released during an ongoing pregnancy, resulting in twins of unequal age.
Superfetation
Placenta can support up to _____________
3000 grams
Determine the gender of the twins (if twins are opposite sex, they are _______________; same-sex twins are indeterminate)
dizygotic
The twin closest to the cervix is ALWAYS called ______________
Baby A
Sonographic observations associated with increased fetal morbidity and mortality:
One gestational sac smaller than the other
Sac appearing “too small” for the fetus
One fetus visibly smaller than the other
Abnormal Doppler tracings
Results from arteriovenous communication between the circulatory systems of monochorionic twins (10-15%)
Recipient twin becomes hypervolemic, large for GA, produces excessive urine leading to hydramnios, heart working hard to pump extra blood (can lead to heart failure)
Donor twin hypovolemic, leading to severe, generally symmetric growth restriction, produces little urine resulting in oligohydramnios; “stuck-twin”
Prognosis is poor for both twins
Twin Transfusion Syndrome
in twin transfusion syndrome what are the two twins called
recipient twin and donor twin
what is the prognosis for twin transfusion syndrome
poor for both twins
Monochorionicity
Marked discordance in AFV
Discordance in size
Larger twin in hydramniotic sac, large bladder, possibly hydropic with enlarged heart
Smaller twin in oligohydramniotic sac, bladder NWV – “stuck-twin”
Check cord Dopplers (🡩 RI?, 🡫, absent, or reversed end-diastolic flow?)
twin transfusion syndrome
Staging of TTTS
Staging of TTTS-Doppler Specifics
treatment of twin transfusion syndrome
-Therapeutic amniocentesis
-Amniotic septostomy
-Fetoscopic laser surgery (occlusion of chorioangiopagous)
80% one twin survives
65-70% both twins survives
<5% have severe disabilities
https://youtu.be/JW-_L5aBQew
-Selective termination
-Hysterotomy with removal of one twin
-Endoscopic umbilical cord ligation
twin transfusion syndrome can be suspected when one twin is at least _____________ larger than the other.
25%
An AC difference of ≥ 20 mm on a scan within 2 weeks of delivery
or
a weight estimation difference > 20% of larger twin’s weight - associated with discordant growth
A 2 week difference in GA is suggestive
helps determine twin transfusion syndrome
-Acardiac parabiotic twin
-Occurs with monozygotic, monochorionic twins or triplets
-Blood flow reverses to acardiac twin
-“Perfused” twin received unoxigenated blood, resulting in aplasia or hypoplasia of the heart, head, and upper limbs
-“Pump” twin is usually normal but may have congestive heart failure and become hydropic
-Associated with hydramnios
-https://www.youtube.com/watch?v=cbo2XLbhjJA
Twin Reversed Arterial Perfusion Sequence (TRAP)
Twin Reversed Arterial Perfusion Sequence (TRAP)
what are the two twins called
perfused and pump twin
-“Perfused” twin received unoxigenated blood, resulting in aplasia or hypoplasia of the heart, head, and upper limbs
-“Pump” twin is usually normal but may have congestive heart failure and become hydropic
Subtypes of TRAP Sequence
Subtypes of TRAP Sequence
Most common
Absence of head and upper torso and limbs
Lower limbs, genitalia and abdominal organs are present.
Acardius Anephus
Subtypes of TRAP Sequence
Least differentiated type
Made up of a mass of bone, muscle, fat, and connective tissue.
Acardius Amorphus
Subtypes of TRAP Sequence
Most developed type
Rudimentary cranial structures, with trunk, limps and abdominal organs.
Lacks rudimentary heart
Acardius Anceps
Subtypes of TRAP Sequence
Rarest
Fetal head is the only developed structure
Umbilical cord insertion is directly into the fetal head
Acardius Acormus
what is this called
Death of a monochorionic twin may be followed by the development of emboli (clots) that can travel to the remaining twin through the placenta causing neurologic damage or injury to other organs including the small intestines and kidneys.
Twin Embolization Syndrome
Results from late and incomplete division of the monozygotic embryonic disk
Most cases have symmetry of joined regions
CONJOINED TWINS
