Twin Embolization Syndrome

2. • A 21 year old previous LSCS lady
• G2P1L1A0
• LMP-GA 30 weeks 5 days
• Intrauterine Monochorionic twin
pregnancy which is confirmed by
ultrasound at 11th week of pregnancy
• No family history of twin pregnancy
• Previous child was normal.

11. US findings
• Intrauterine monochorionic twin gestation
• Twin 1
• Gross ventriculomegaly with thinned out
cerebral mantle
• Multiple dilated small bowel loops s/o
small bowel atresia
• Non visualisation of left kidney
• No e/o spinal anomaly
• No e/o cardiac anomaly

12. US findings…
• Twin 2
• Fetus papyraceous
• Side to side compressed head
• Compressed body

13. Diagnosis
• Twin embolisation syndrome /
vanishing twin syndrome

22. Discussion

23. Multiple gestation

24. Zygosity
• Zygosity
• Genetic makeup of the pregnancy
• Is determined by type of fertilization, i.e.
monozygotic or dizygotic
• Zygosity can only be determined by
genetic analysis of both fetuses
• USG can be used to determine the
likelihood of zygosity

25. Chorionicity
• Chorionicity
• Membrane complement of the pregnancy
• Is determined by the occurrence and
timing
• Determined non-invasively by
ultrasound

27. Dizygotic Pregnancy
• Twins resulting from 2 ova fertilized by
2 sperm
• These are ALWAYS dichorionic
• Fused or separated

28. Monozygotic
Pregnancy
• One ovum
fertilized by one
sperm that
subsequently splits

31. Chorionicity

32. Chorionicity - USG
• Ultrasound detection of two separate
placentas.
• Confirms a dichorionic pregnancy
• The detection of different-sex fetuses.

33. Chorionicity
• Ultrasound detection of a single
placenta
• Either monochorionic or
dichorionic (fused placenta)

34. Chorionicity
• Thick inter-twin membrane
• Often taken as > 2 mm
• All membranes look thin in third
trimester
• Count layers with high resolution
transducer, if ≥ 2 must be DC

37. "Twin peak" or Lambda sign
• Chorionic tissue extends into inter-twin
membrane at placenta
• Chorion forms echogenic triangle
• Triangle base on placental surface, apex
fades into inter-twin membrane
• Reliable indicator of dichorionicity

39. Chorionicity

40. "T" sign
• Absent "twin-peak"
• Membrane abuts placental surface
without triangle of chorionic tissue
• Does NOT exclude dichorionicity
• Monochorionic pregnancies have a thin
wispy membrane between the sacs
made up of two layers of amnion and
generally less than 1 mm in thickness

42. Chorionicity

43. Dichorionic diamniotic
pregnancy
Visualization of two
placentas and a dividing
membrane ("half twin
peak" sign) or
Visualization of one
placenta and a dividing
membrane, plus a lambda
sign
Monochorionic
diamniotic pregnancy
Visualization of one placenta
and a dividing membrane, plus
a T sign
Monochorionic
monoamniotic
pregnancy
Visualization of one placenta;
dividing membrane and T sign
are not visualized

44. Zygosity - USG
• Twins are definitely dizygotic if they
are of different sexes.

45. Monozygotic twins
• Single gestational sac with only one
placenta
• Intertwined two umbilical cords
• Conjoined twin

46. Complication of multiple
pregnancy
• DICHORIONIC DIAMNIOTIC TWINS
• Maternal complications> singleton
pregnancy
o Hypertension
o Preeclampsia
o Antenatal hemorrhage
• Placenta previa
• Placental abruption
• Other causes

47. o Postpartum hemorrhage
• Perinatal mortality reported 10%
o Preterm delivery
• Median gestational age (GA) twins at
delivery 36 weeks
o Intrauterine growth restriction
o Anomalies

48. MONOCHORIONIC TWIN
• MONOCHORIONIC DIAMNIOTIC
TWIN
 Vanishing twin
 Discordant twin growth
 TTTS
 Twin embolisation syndrome
 Parasitic twin (acardiac acranius)/(TRAP
sequence)

49. MONOCHORIONIC TWIN
• MONOCHORIONIC
MONOAMNIOTIC TWIN
Discordant twin growth
TTTS
Conjoined twins
Tangled umblical cords

50. Discordant twin growth
• May occur in monochorionic or
dichorionic pregnancies
• Monochorionic more common
• Discordant growth
One twin with intrauterine growth restriction
• EFW < 10th percentile
• AC difference > 20mm
• EFW difference > 20%

51. USG
• Crown rump length disparity in first
trimester predictor for discordant birth
weight
• Series dichorionic pregnancies with
demise/anomalies excluded
• CRL difference> 3 days at 11-14 weeks
gestational age

52. USG
• Oligohydramnios about smaller twin
• Sign of placental insufficiency
• May also occur with anomaly or
aneuploidy
• Twin-twin transfusion syndrome
unlikely unless monochorionic twins
and polyhydramnios around other fetus

53. Color Doppler
• UmA
• Significant difference in SD ratio> 15%
between twins
• SD ratio difference > 0.4 between twins has
also been used to predict discordance

54. Vascular anastomoses between
fetus
• Present only in monochorionic twin
placentas.
• Nearly 100% of monochorionic twin
placentas have vascular anastomoses,but
there are marked variations in the number,
size, and direction.
• A-A anastomoses on the chorionic surface
of the placenta have been identified in up
to 75%.

56. Type of anastomoses

57. TTTS (Twin to Twin
Transfusion Syndrome)
• Incidence : 4 - 20%
of MC twins
• It is characterised
by an imbalance of
blood flow between
the twins
• 15 - 20% of perinatal
deaths in twins

59. • Donor twin
Hypovolemia
Hypotension, decreased
venous return
Growth retardation,
anemia
Heart failure
Hydrops
Intrauterine death
• Recipient twin
Hypervolemia
Hypertension, increased
venous return
Myocardial hypertrophy,
plethora
Heart failure
Hydrops
Intrauterine death

60. Ultrasound signs of TTTS
• Detection of monochorionic placenta with
different echogenicities
• Detection of concordant external genitalia
• Growth discordance between the twins
 Discrepancy in abdominal circumference > 20
mm or
 Weight discrepancy > 20% relative to the larger
twin
• Unequal amniotic fluid volumes
 Donor: oligohydramnios (stuck twin)
 Recipient: polyhydramnios

61. • Unequal bladder filling
 Donor little or no visible bladder filling
 Recipient: well-distended bladder
• Unequal umbilical cord thickness
 Donor: thin umbilical cord,
 Recipient: thick umbilical cord
• Hydrops of one fetus
• Marked discrepancy in Doppler findings (umbilical
artery) between the two umbilical cords
 S/D ratio discrepancy > 0.4
• Color Doppler: development of tricuspid
insufficiency in the recipient
• Vascular anastomoses in the chorionic plate may be
directly visualized with color Doppler

62. Staging of TTTS
• Stage 1: Donor bladder visible, normal
Doppler
• Stage 2: Donor bladder empty, normal
Doppler
• Stage 3: Donor bladder empty, abnormal
Doppler
• Stage 4: Hydrops in recipient
• Stage 5: Demise of one or both

63. TTTS (Twin to Twin Transfusion Syndrome)
Diamniotic Gestation with Stuck Twin

64. Twin Embolization Syndrome
• Uncommon
• Death of One Twin In Utero
• Blood Products from Dead Twin
Shunted
• Results
• Disseminated Intravascular Coagulopathy
• Multifocal Tissue Infarction

65. Twin Embolization Syndrome
Passage of thromboplastin like material on
embolic debris into the circulation of the
surviving twin
A variety of ischemic or vascular disruptive
defects of the central nervous system,
gastrointestinal tract, on genitouninamy
tract.

66. Twin embolization syndrome:
Current theory
• Twin demise => loss of peripheral resistance
• Vascular anastomoses between twins due to
monochorionic placentation
• Abrupt drop in peripheral resistance secondary to
demise hypotension in live twin
o End result is "hypoperfusion" lesions of brain and
kidneys
 Intraventricular hemorrhage
 Porencephaly
 Periventricular leukomalacia
 Renal infarction

67. Twin Embolization Syndrome
• CNS anomalies
 Fetal ventriculomegaly
 Porencephalic cyst
 Fetal cerebral atrophy
 Cystic encephalomalacia
 Microcephaly
• GI anomalies
 Hepatic and splenic infarcts
 Small bowel atresia
 Gastroschisis

68. Twin Embolization Syndrome
• Genitourinary Anomalies
Fetal Renal Cortical Necrosis
Horse shoe kidney
• Other findings
Fetal Hydrothorax
Pulmonary Infarcts
Hemifacial microsomia
Aplasia cutis congenita
Terminal Limb Defects

69. TRAP (Twin Reversed Arterial
Pressure)
• Acardiac Monster
• Extremely Rare <1:25000
• Large arterio-arterial anastomosis
• “Pump” & “Perfused” twins
• Perinatal mortality in the pump twin is
55%, due to polyhydramnios and
cardiac failure

71. USG
Acardiac twin
• Dysmorphic with edema and cyst
formation in soft tissues
• No cardiac structures or activity
• Often no identifiable cranial structures
• Presence and structure of upper
extremities variable
• Usually recognizable torso and lower
extremities

72. USG
• Lower extremities move spontaneously
• Single umbilical artery in 66% of
acardiac twins
• Polyhydramnios
• Strong correlation with presence of
renal tissue in acardiac twin
• Increases risk for premature labor

74. CONJOINED TWINS
• Thoracopagus: Fused at chest
• Omphalopagus: Fused xiphoid to
umbilicus
• Thoraco-omphalopagus: Extensive
chest and abdominal fusion
• Pygopagus: Fused at buttocks
• Ischiopagus: Fused at hips
• Craniopagus: Fused at cranial level

75. Craniopagus occipitalis. Cephalothoracopagus
monosymmetros.
Thoracopagus.
Pygopagus.
Ischiopagus.

76. CONJOINED TWINS
• Symmetrical conjoined twins ("Siamese
twins")
• Asymmetrical conjoined twins (autosite
and parasite)

77. Symmetrical conjoined twins
• Same-sex twins that are joined at certain
body sites
• Often called "Siamese twins"
• Forms
 Complete symmetrical conjoined twins
 Incomplete symmetrical conjoined twins

78. • Complete form
• Both twins are equally well developed and
are conjoined at certain body regions.
• Incomplete form
• The superior or inferior part of the body is
duplicated in varying degrees

79. Omphalopagus twins shows a
fused liver

80. Common heart

81. Asymmetrical conjoined twins
• One is complete than the other, fully
developed twin (autosite)