1. family and parenting
2. motherhood
3. pregnancy

BETH ISRAEL DEACONESS
MEDICAL CENTER
HARVARD
MEDICAL
SCHOOL
Perinatal mortality
Sonography of Twins
Deborah Levine, MD
Gezer, Arch Gynecol Obstet (2012) 285:353–360
Cerclage in twins
Risks
Di-di
preterm delivery - check the cervix!
IUGR
congenital malformations
Di-mo
twin twin transfusion syndrome
Mo-mo
cord entanglement
Rates of very low birthweight and of respiratory distress syndrome were
significantly higher in the cerclage compared to the control group….
Based on these Level 1 data, cerclage cannot currently be recommended
for clinical use in twin pregnancies with a maternal short cervical length
in the second trimester.
RDS
Dextrocardia
Malrotation
Acta Obstet Gynecol Scand. 2015
2/3 of all twins
1/3 of all twins
Twin Morbidity
1%
1/3
Survey of 33,873 women, 1.3% twins
• Preterm delivery
– 54% of twins
– 9.6% of singletons
2/3
Monozygotic
Day 3
di-di (33%)
Day 4-7
di-mo (66%)
Day 7-12
mo-mo (1%)
Day 13-21
conjoined
1/50,000-1/100,000 births
• 15.4% of neonatal deaths
• 9.5% of fetal deaths
Gardner et al, Obstet Gynecol 1995
Image from: Larsen, WJ
Human embryology
1
Twins
Multiple Gestations
• Dizygotic (2/3 of twins)
– maternal age
– race
– parity
Chorionicity is most accurately
determined in the first trimester
• Monozygotic (1/3 of twins)
– 1/250
Why Do Endovaginal Scanning?
Amnionicity/Chorionicity
Di-Di
Thick membrane (> 2 mm) - 92%
2 Placenta sites - another 4%
Di-Mo
Thin membrane
(< 1 mm) - 88%
Transabdominal
“Empty Sac”
Transvaginal
Di-Mo Twins!
Chorionicity
•
•
•
•
Discordant twins
Twin-twin transfusion
Congenital abnormalities
Fetal death of one twin
– Di-Di allow pregnancy to continue
– Di-Mo at risk for anomalies/demise
*Kurtz, Radiology 1992
Di-Di Twins
• Different sex
• Separate placentae
• Thick membrane
(>2mm)
• “Twin peak”
• Amniocentesis
2
Diamniotic Monochorionic Twins
Finberg, JUM 1992
Twin
Peak
Twin mimic: Synnechia
Twin Mimic: Bicornuate Uterus
Decidual reaction in other horn, not twin
3
IVF population:
beware heterotopic multiple gestations
Regardless of history: make sure they are in
the uterus
Dichorionic Triamniotic Triplets
1
2
?3
Early counting of Twins
Twins at > 6 weeks who were studied
at 5-5.9 weeks
–24/213 (11%) Di-Di twins missed
–6/7 (86%) Di-Mo twins missed
Vanishing Twin
• 21% of twins verified to be alive with
sonography disappeared subsequently*
• Late 1st trimester, early 2nd trimester
• No significant risk to the living co-twin
Doubilet, JUM 1998
– Landy, Obstet Gynecol 1986
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1
2
7 weeks, 2 sacs
One with fetal pole with FH
Smaller sac with yolk sac, no FH
10 weeks, 1 live fetus
Second empty sac
Twins of Different Sizes
Fetus Papyraceous
• Small non-viable fetus in a small sac
• Flattening, necrosis, atrophy
• 1/184 twin births
Twin Anomalies
• Embryologic hypothesis
– Monozygous twinning is a result of abnormal
embryologic development
– Therefore is associated with other anomalies
5
Growth Discordance
So, are they identical?
Weight discordance > 20% is worrisome
Monochorionic twins
• 6 weeks, two
heartbeats
• 40% 2 liveborn
• 30% 1 liveborn
• 30 % 0 liveborn
Stuck Twin
• 12 weeks, two
heartbeats
74.5 % 2 liveborn
0.5 % 1 liveborn
25.0 % 0 liveborn
Benson, Radiology, 1994
Twin Twin Transfusion
• Occurs in 4-35% of monochorial multiple
gestations
• Perinatal mortality >80% (17% of twin
mortality
• Vascular anastomoses
Twin Twin Transfusion
• Donor twin
– Anemia
– Growth retardation
– Oligohydramnios
• Recipient twin
– Polyhydramnios
– Polycythemia
– Hydrops
6
Placental Anastomoses
Placental Anastomoses
• 20 sets of twins with and without TTS
• Placentas from pregnancies with TTS had
fewer anastomoses than controls
• No significant correlation between the
number of anastomoses and the intercord
distance
• Location
– Superficial
– Deep
• Type
– A-A (common, superficial)
– V-V (rare)
– A-V (unequal sharing)
Bajoria et al, Am J Obstet Gynecol 1995
A-A Anastomosis
A-V Anastomosis
Images courtesy of V. Feldstein, UCSF
Images courtesy of V. Feldstein, UCSF
Twin Twin Transfusion
Therapy
•
•
•
•
Amnioreduction
Laser ablation of placental anastomoses
Selective feticide
These have reduced fatalities by 50%
From: Vickie Feldstein MD, in Callen, PW
4th edition, Ultrasound in Obstetrics
and Gynecology
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TAPS (Twin anemia / polycythemia )
• Doppler increase MCA-PSV >1.5 MoM in
one fetus with a decrease in MCA-PSV of
<0.8 MoM in the co-twin.
• Postnatal TAPS inter-twin hemoglobin
difference of ≥ 8 g/dL at birth and at least
one of
– reticulocytosis in the donor with an inter-twin
reticulocyte count ratio >1.7
– presence of only small (<1 mm in diameter)
residual anastomoses seen at the time of
postnatal placental injection studies
Long term neurologic outcome after TTS
Studies
(fetuses)
Amnioreduc‐ 3(182)
tion
Laser
7(1428)
therapy
Postnatal
f/u
(months)
Perinatal
mortality
Mild
Survivors
withknown impaired
outcome‐
normal
Severely
impaired
36‐144
55%
14‐72
31%
43/54
(80%)
274/325
(84%)
13/73
(18%)
115/969
(12%)
3/54
(6%)
22/325
(7%)
“when addressing neurological risks associated with any intervention,
what are the baseline risks to a survivor without intervention?”
No
treatment
1 (94)
48%
18/40
(45%)
13/40
(33%)
9/40
(9%)
Quintero Staging TTS
• I
MVP <2 cm in donor sac; MVP >8 cm in
recipient sac; both twins bladder present
II
Absence of urine-filled bladder
III
Absent/reverse end diastolic flow UA
Reverse flow ductus venosus
Pulsatile umbilical venous flow
IV
Ascites, pericaridal/pleural effusion, hydrops
V
Death of one of the twins
“Solomon technique”
• In patients with TTTS, photocoagulation of
causative anastomoses and the chorionic
plate along the vascular equator decreases
recurrence without increasing adverse
outcome and improves survival compared
with the selective technique
• Hope is that long term studies will also
show improved outcomes
Gebb J. Am J Obstet Gynecol. 2014 Epub ahead of print
Fluid Discordance
Co-twin Demise
Monochorionic Pairs
• Cerebral palsy
8
Twin Anomalies
• Thromboembolic vs. ischemic
–
–
–
–
–
–
–
Acardiac Twin
chorioangiopagus parasiticus
•
•
•
•
1% monochorionic twins
Umbilical arterial to arterial anastomoses
Pulsatile flow to internal iliac arteries
Structures supplied by the distal abdominal
aorta and iliac arteries are developed best
• Upper trunk and head are not perfused
microcephaly
multicystic encephalomalacia
hydrocephaly
hydranencephaly
limb amputation
intestinal atresia
aplasia cutis
Acardiac Twin
• Blood retrograde from
normal to abnormal fetus
• Retrograde flow in umbilical
cord of acardiac twin
• Cardiac failure and death of
the normal twin in 50%
– Additional workload increases
in third trimester when size of
the acardiac twin becomes
larger
Image from Rodeck, NEJM, 1998: 1294
9
Amniocentesis in Monzygotic Twins
• Usually have the same karyotype
• Rare postzygotic nondysjunction
• Turner and normal male; Mosaic Turners
10
Mo-Mo twins
• One yolk sac
• Need to follow-up, since with early
di-mo twins, only one yolk sac may be seen
Mo-Mo Twins
• Conjoined twins
• Cord entanglement
– perinatal mortality 30-70%
? Conjoined?
• Monitor heart tracings
• Deliver early
Bromley, JUM 1995
Move independently
Cord Entanglement
• 7 nonconjoined monoamniotic twins
– Cord entanglement seen in 4
– Missed in one
Aisenbrey et al ObGyn 1995
11
Intertwined Cords
Conjoined twins
• 1/50,000 births
• Mo-mo
• After 13 days and before the
third week
• Site and extent of fusion
varies
• Congenital anomalies separate
from region of union
Conjoined twins
• Suffix -pagus, “fastened”
– Craniopagus
– Thoracopagus
– Omphalopagus
• Thoracoomphalopagus
most common
12
Conjoined twins
30 weeks
single kidney & bladder
Day 10
Images courtesy of Dr. Barnewolt, Boston
Images from S. Sinnott
Summary: TWINS
• Congenital abnormalities
• F/U - growth - Discordant twins
• Chorionicity is important
– Twin-twin transfusion
– Fetal death of one twin
• Di-Mo at risk for anomalies/demise
– Amniocentesis
• Amnionicity is important
– Monoamniotic twins at high risk
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