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Vickie Vickie A A Feldstein, Feldstein, MD & Larry Rand, MDMD & Larry Rand, MD

Departments Departments of Radiology of Radiology andandObstetrics, Gynecology & Reproductive SciencesObstetrics, Gynecology & Reproductive Sciences

University of California, San University of California, San FranciscoFrancisco

Ultrasound in theUltrasound in theEvaluation andEvaluation andManagement ofManagement ofTWINSTWINS

Ultrasound in TwinsUltrasound in Twins

1stTrimester

1stTrimester

2ndTrimester

2ndTrimester

3rdTrimester

3rdTrimester

Ultrasound in TwinsUltrasound in Twins

1stTrimester

1stTrimester

2ndTrimester

2ndTrimester

3rdTrimester

3rdTrimester

���� Monochorionic versus Dichorionic

���� Complications of Monochorionicity

���� Focus on Growth and Fluid

���� High-risk issues to consider

US & US & Multiple GestationsMultiple Gestations

PerinatalPerinatal complications are more common complications are more common in twin pregnancies:in twin pregnancies:

•• PTL, HTN, PTL, HTN, Fetal anomalies, Poly/Fetal anomalies, Poly/OligoOligo, , IUGR, IUGR, Fetal demise, Fetal demise, MalpresentationMalpresentation, Abruption, , Abruption, PreviaPrevia, Postpartum , Postpartum hemorrhagehemorrhage

•• PerinatalPerinatal mortality rate 4mortality rate 4--10X that of singletons10X that of singletons•• Risks differ with Risks differ with chorionchorion/amnion types/amnion types•• Ultrasound is critically Ultrasound is critically important!important!

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from Larsen WJ: Human Embryology, 2nd ed NY, Church ill Livingstone, 1997from Larsen WJ: Human Embryology, 2nd ed NY, Church ill Livingstone, 1997

DizygoticDizygotic (“fraternal”)(“fraternal”)

from Larsen WJ: Human Embryology, 2nd ed NY, Church ill Livingstone, 1997from Larsen WJ: Human Embryology, 2nd ed NY, Church ill Livingstone, 1997

MonozygoticMonozygotic(“identical”)(“identical”)

ZygosityZygosity && ChorionicityChorionicity

•• DIDI--chorionic =chorionic =EITHER MonoEITHER Mono-- or Dior Di--zygotic twinszygotic twins

•• MONOMONO--chorionic = Monochorionic = Mono--zygotic twinszygotic twins

FIRST TRIMESTER:FIRST TRIMESTER:Important Ultrasound ObservationsImportant Ultrasound Observations

•• Accurate head count!Accurate head count!

Undercounting is easy, Undercounting is easy, espesp with MC twinswith MC twins

Outcomes are better when detected Outcomes are better when detected earlyearly

•• NTNT

•• MOST MOST critical piece of information:critical piece of information:

CHORIONICITY!CHORIONICITY!

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ChorionicityChorionicity

•• Chorionicity is the most important U/S Chorionicity is the most important U/S predictor of outcome for twinspredictor of outcome for twins

•• Under 14 weeks, can be detected with Under 14 weeks, can be detected with 99% sensitivity and 100% specificity99% sensitivity and 100% specificity

•• Chorionicity determination when <14 Chorionicity determination when <14 weeks is considered the weeks is considered the standard of carestandard of care

DichorionicDichorionic DiamnioticDiamniotic

DichorionicDichorionic DiamnioticDiamniotic MonochorionicMonochorionic DiamnioticDiamniotic

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DichorionicDichorionic DiamnioticDiamniotic

What would you say…………?

MonochorionicMonochorionic DiamnioticDiamniotic

What would you say…………?

MonochorionicMonochorionic DiamnioticDiamniotic

FIRST TRIMESTER: FIRST TRIMESTER: Risk CorrelationRisk Correlation

Why all the fuss?Why all the fuss?

Determining Determining CHORIONICITYCHORIONICITY will:will:

–– Influence ultrasound plan and Influence ultrasound plan and surveillance for the pregnancysurveillance for the pregnancy

–– Inform overall pregnancy risk counselingInform overall pregnancy risk counseling

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If DICHORIONICIf DICHORIONICUS Plan: US Plan:

–– Twin anatomyTwin anatomy–– Monthly growth scansMonthly growth scans–– Cervical length Cervical length –– 2 2 placentationsplacentations: rule out : rule out previaprevia

Genetics:Genetics:–– Assume Assume dizygoticdizygotic; increases risk of aneuploidy ; increases risk of aneuploidy

(AMA pts)(AMA pts)

Overall Risks:Overall Risks:–– Usual twins risks:Usual twins risks:

•• PTB/PTL, cervical shortening, abruption, PTB/PTL, cervical shortening, abruption, previaprevia, IUGR, pre, IUGR, pre--eclampsiaeclampsia, diabetes, PPH, etc, diabetes, PPH, etc

If MONOCHORIONIC:US Plan:US Plan:

–– Level II twin anatomy Level II twin anatomy –– q2 week fluid pockets & growth (q2 week fluid pockets & growth (espesp 1616--28 weeks) 28 weeks)

•• Fluid discordance, TTTS, unequal placental sharingFluid discordance, TTTS, unequal placental sharing•• Frequent 3rd trim due to increased risk IUFDFrequent 3rd trim due to increased risk IUFD

–– Cervical lengthCervical length

Genetics:Genetics:–– Must be monozygotic; risk of aneuploidy equals Must be monozygotic; risk of aneuploidy equals

that of a singleton fetusthat of a singleton fetus

Overall risks:Overall risks:–– Compared to DC twins: higher risks of IUFD, PTB Compared to DC twins: higher risks of IUFD, PTB

<32wk (2x), IUGR (4x), SAB (6x), CP (8x)<32wk (2x), IUGR (4x), SAB (6x), CP (8x)

Cervical Length in Twins

•• Serial cervical length measurement may aid Serial cervical length measurement may aid in identifying patients at riskin identifying patients at risk–– <1.5 cm <1.5 cm at increased riskat increased risk

•• CerclageCerclage for USfor US--detected cervical shortening detected cervical shortening in twins very controversialin twins very controversial

•• Common protocol: b/w 16 to 24/28wksCommon protocol: b/w 16 to 24/28wks•• Targeted scan: Targeted scan: transvaginaltransvaginal / / translabialtranslabial

•• CervixCervix•• CHORIONICITY (if unknown)CHORIONICITY (if unknown)•• Anomalies (increased in twins)Anomalies (increased in twins)•• Fetal Fetal size and AFV size and AFV –– r/or/o discordancediscordance

SECOND TRIMESTER:Important Ultrasound Observations

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U/S Clues:U/S Clues:

SECOND Trimester SECOND Trimester ChorionicityChorionicity

Placental NumberPlacental NumberFetal GenderFetal Gender“Twin Peak” Sign, if present“Twin Peak” Sign, if presentMembrane ThicknessMembrane Thickness

2 Placental Masses 2 Placental Masses �������� DichorionicDichorionic

PP

PP

XY & XX XY & XX ��������DizygoticDizygotic ��������DichorionicDichorionic

MonochorionicMonochorionicDichorionicDichorionic

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“Twin Peak” Sign“Twin Peak” Sign

indicates DICHORIONIC twin pregnancyindicates DICHORIONIC twin pregnancy

Membrane ThicknessMembrane Thickness

MonochorionicMonochorionic DiamnioticDiamniotic

SECOND TRIMESTER US:

•• All things being equal, 2All things being equal, 2 ndnd trim focus trim focus is on MC TWIN COMPLICATIONSis on MC TWIN COMPLICATIONS

–– WHYWHY do some MC twins develop do some MC twins develop complications?complications?

–– WHATWHAT is TTTS?is TTTS?–– Not allNot all complications are TTTS!complications are TTTS!

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A placenta is designed to A placenta is designed to support 1 fetussupport 1 fetus

When 1 placenta supports 2 When 1 placenta supports 2 fetuses, no set plan/roadmapfetuses, no set plan/roadmap

Each MC placenta is like a Each MC placenta is like a ‘snowflake’‘snowflake’

How the circulations interact How the circulations interact ((angioarchitectureangioarchitecture ) will be ) will be uniqueunique

Placental Vascular AnatomyPlacental Vascular Anatomy

Geoffrey A Geoffrey A MachinMachin, MD PhD, MD PhD

Placental Vascular AnatomyPlacental Vascular Anatomy

SHARING of placental territory and CROSSSHARING of placental territory and CROSS--TALKTALKInterInter--twin Vascular CONNECTIONS twin Vascular CONNECTIONS –– number, size, typenumber, size, type

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ArterialArterial--Venous Venous AnastomosisAnastomosis ArterioArterio--Arterial Arterial AnastomosisAnastomosis

ArterioArterio--Arterial Arterial AnastomosisAnastomosis Doppler Interrogation for an ADoppler Interrogation for an A--A: A: start with umbilical cord insertion sitesstart with umbilical cord insertion sites

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Color Doppler of AColor Doppler of A--A A AnastomosisAnastomosis • AAs are detectable by antenatal ultrasound

• AAs associated with: 10-fold reduction in TTTS and 7-fold reduction in IUFD

Donor

Recipient

Twin Twin Transfusion Syndrome (TTTS)

• May or may not be weight discordant

• Staging:– Based on bladders,

Dopplers, ?hydrops

• True TTTS carries up to 90% dual mortality rate

• Both donors and recipients face other organ morbidities

Oligohydramnios/PolyhydramniosOligohydramnios/Polyhydramnios

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“Stuck” Twin / Donor“Stuck” Twin / Donor OligohydramniosOligohydramnios / / PolyhydramniosPolyhydramnios

Recipient. DVP > 8cmRecipient. DVP > 8cmDonor. DVP < 2cmDonor. DVP < 2cm

DonorDonor

RecipientRecipient

EFW discordanceEFW discordance(346 (346 -- 197) 197) ÷÷÷÷÷÷÷÷ 346 = 43 %346 = 43 %

Minimally invasiveSingle port3 mm device

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Laser Ablation of TTTS

Discordant size ≠ TTTSDiscordant size ≠ TTTS

Unequal Placental SharingUnequal Placental Sharing

Cord Insertions

Central

Velamentous

Equator

Central

Velamentous

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Unequal Placental Sharing

Sub-optimal growthPossible Oligo

Normal growthNormal fluidNo poly

Umbilical Cord Insertion SiteUmbilical Cord Insertion Site

% Weight Discordance: (295 % Weight Discordance: (295 –– 206) 206) ÷÷÷÷÷÷÷÷ 295 = 30 %295 = 30 %

Monochorionic Pregnancies

TTTS≈ 10%

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Monochorionic Pregnancies

Discordant EFWs

TTTS≈ 10%

Monochorionic Pregnancies

Unequal Sharing

TTTS≈ 10% AFV =

WNL/WNL WNL/Oligo

AFV = Poly AND Oligo

•• GrowthGrowth•• Amniotic Fluid VolumeAmniotic Fluid Volume•• Delivery planning:Delivery planning:

–– PositionPosition–– Presentation (A, B)Presentation (A, B)–– EFW (EFW (espesp nonnon--presenting)presenting)

THIRD TrimesterTHIRD TrimesterImportant Important Ultrasound Ultrasound ObservationsObservations IUFD of one twinIUFD of one twin

•• Are Are theythey MC MC oror DCDC??MCMC = surviving co= surviving co--twin has high risk of twin has high risk of

neurologic injury (up to 40%) from neurologic injury (up to 40%) from ischemia (vascular connections)ischemia (vascular connections)

•• Consider fetal MRI, best sensitivity for ischemic Consider fetal MRI, best sensitivity for ischemic injuryinjury

DCDC = = surviving twin not typically at risk surviving twin not typically at risk unless ongoingunless ongoing maternal processmaternal process

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ConclusionsConclusions

•• Twins have increased risk of perinatal Twins have increased risk of perinatal complicationscomplications vs. singletonsvs. singletons

•• MCMC more more complications than DC twinscomplications than DC twins•• Management of twin pregnancies Management of twin pregnancies

depends ondepends on knowledge knowledge of of chorionicitychorionicity!!

•• CHORIONICITY can be determined by USCHORIONICITY can be determined by US•• Assessment is easiest in 1st TrimesterAssessment is easiest in 1st Trimester•• US Examination and Report should address US Examination and Report should address

CHORIONICITY!CHORIONICITY!•• Note: Discordant weight and fluidNote: Discordant weight and fluid•• Unequal Placental SharingUnequal Placental Sharing•• Vascular Vascular AnastomosesAnastomoses in shared placentain shared placenta

Ultrasound in TwinsUltrasound in Twins

1stTrimester

1stTrimester

2ndTrimester

2ndTrimester

3rdTrimester

3rdTrimester

--Head countHead count--ChorionicityChorionicity--NTNT

--AnatomyAnatomy--Serial growth Serial growth & fluid& fluid--Serial cervixSerial cervix--MC MC surveillancesurveillance

--Continued MC Continued MC surveillancesurveillance--Growth/fluidGrowth/fluid--PresentationsPresentations--Delivery Delivery planningplanning