INTERESTING CASE PRESENTATIONDr. A. JEYARAMAN, D.M.R.D., TUTOR,

Dr. S. THIYAGARAJAN, II YR D.M.R.D. – PG

DEPARTMENT OF RADIOLOGYGOVERNMENT RAJAJI HOSPITAL

MADURAI

• 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.

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

US findings…

• Twin 2• Fetus papyraceous• Side to side compressed head• Compressed body

Diagnosis

• Twin embolisation syndrome / vanishing twin syndrome

Discussion

Multiple gestation

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

Chorionicity

• Chorionicity• Membrane complement of the

pregnancy• Is determined by the occurrence and

timing• Determined non-invasively by

ultrasound

Dizygotic Pregnancy

• Twins resulting from 2 ova fertilized by 2 sperm

• These are ALWAYS dichorionic• Fused or separated

Monozygotic Pregnancy

• One ovum fertilized by one sperm that subsequently splits

Chorionicity

Chorionicity - USG

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

Chorionicity

• Ultrasound detection of a single placenta

• Either monochorionic or dichorionic (fused placenta)

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

"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

Chorionicity

"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

Chorionicity

Dichorionic diamniotic pregnancy

Visualization of two placentas and a dividing membrane ("half twin peak" sign) orVisualization 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

Zygosity - USG

• Twins are definitely dizygotic if they are of different sexes.

Monozygotic twins

• Single gestational sac with only one placenta

• Intertwined two umbilical cords• Conjoined twin

Complication of multiple pregnancy

• DICHORIONIC DIAMNIOTIC TWINS• Maternal complications> singleton

pregnancyo Hypertensiono Preeclampsiao Antenatal hemorrhage

• Placenta previa• Placental abruption• Other causes

o Postpartum hemorrhage• Perinatal mortality reported 10%

o Preterm delivery• Median gestational age (GA) twins at delivery 36 weeks

o Intrauterine growth restrictiono Anomalies

MONOCHORIONIC TWIN

• MONOCHORIONIC DIAMNIOTIC TWIN Vanishing twin Discordant twin growth TTTS Twin embolisation syndrome Parasitic twin (acardiac

acranius)/(TRAP sequence)

MONOCHORIONIC TWIN

• MONOCHORIONIC MONOAMNIOTIC TWINDiscordant twin growthTTTSConjoined twinsTangled umblical cords

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%

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

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

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

Vascular anastomoses betweenfetus

• 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%.

Type of anastomoses

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

• Donor twinHypovolemia

Hypotension, decreased venous

return

Growth retardation, anemia

Heart failure

Hydrops

Intrauterine death

• Recipient twinHypervolemia

Hypertension, increased venous

return

Myocardial hypertrophy, plethora

Heart failure

Hydrops

Intrauterine death

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

• 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

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

TTTS (Twin to Twin Transfusion Syndrome)

Diamniotic Gestation with Stuck Twin

Twin Embolization Syndrome

• Uncommon• Death of One Twin In Utero• Blood Products from Dead Twin

Shunted• Results

• Disseminated Intravascular Coagulopathy

• Multifocal Tissue Infarction

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.

Twin embolization syndrome: Current theory

• Twin demise => loss of peripheral resistance• Vascular anastomoses between twins due tomonochorionic placentation• Abrupt drop in peripheral resistance secondary todemise hypotension in live twino End result is "hypoperfusion" lesions of brain andkidneys

Intraventricular hemorrhage Porencephaly Periventricular leukomalacia Renal infarction

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

Twin Embolization Syndrome

• Genitourinary AnomaliesFetal Renal Cortical NecrosisHorse shoe kidney

• Other findingsFetal HydrothoraxPulmonary InfarctsHemifacial microsomiaAplasia cutis congenitaTerminal Limb Defects

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

USGAcardiac 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

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

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

Craniopagus occipitalis. Cephalothoracopagus monosymmetros. Thoracopagus.

Pygopagus.

Ischiopagus.

CONJOINED TWINS

• Symmetrical conjoined twins ("Siamese twins")

• Asymmetrical conjoined twins (autosite and parasite)

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

• 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

Omphalopagus twins shows a fused liver

Common heart

Asymmetrical conjoined twins

• One is complete than the other, fully developed twin (autosite)