With the use of fertility enhancing medications, advance maternal age pregnancies and just the natural order od twinning, this pregnancy presentation has become more common among providers. Here we explore the etiology, presentation and management of twin pregnancies.

1. TWIN GESTATION
By La Lura White MD
Maternal Fetal Medicine

2. TWIN GESTATION
 Multiple gestations have become one of the most
common high-risk conditions encountered by the
practicing obstetrician/gynecologist.
 Since 1980, the number of twins delivered in the
United States has risen over 80%, mainly
secondary to ART, ovulation induction agents
and AMA.
 Now twins represent approximately 3% of all live
births.

3. TWIN GESTATION
 Despite the fact they account for only a small percentage
of all live births, they are responsible for a
disproportionate share of perinatal morbidity and
mortality:
 17% of all preterm births less than 37 weeks, 23% of
early preterm births less than 32 weeks, 24% of all low–
birth-weight (LBW) (<2,500 g) 26% of all very low–
birth-weight (VLBW) (<1,500 g).
 Because of the increased prematurity and LBW, twins are
at an approximate 7-fold greater risk of dying before their
first birthday compared with singletons.

4. TWIN GESTATION
 Epidemiology :Twin birth rate in the United States
33.3 per 1,000 births
 Japan: 6.7/1000 (lowest)
 Africa: 40/1000 (highest)
 Triplets are about 1 in 7,500 births (1/5 major
handicap)
 Quadruplets are about 1 in 650,00 births (1/2 major
handicap)

5. TWIN GESTATION
 Average birth weight 2,347 g
 Average gestational age at delivery 35.3
wk

6. TWIN GESTATION
 Multifetal gestations also are associated with significantly
higher maternal morbidity and associated health care costs.
 6 times more likely to be hospitalized with complications.
 Hospital costs for women with multiple gestations are on
average 40% higher than for women with gestational-age
matched singleton pregnancies.
 Neonatal intensive care unit (NICU) admission is required:
one fourth of twins
three fourths of triplets,
virtually all quadruplets
average NICU stays
 18 days (twins), 30 days (triplets), 58 days(quads)

7. TWIN GESTATION
 Monozygotic: (33%)
 Splitting of an embryo after
fertilization.
 Identical
 Dizygotic: (67%)
 Fertilization of more than
one egg.
 Non-identical

8. TWIN GESTATION
 Dizygotic
 Incidence varies
 Race: 7 to 10/1,000 Caucasian,
10 to 40 /1,000 African
descent, 3 /1,000 Asians
 Personal hx (2X)
 Family hx (maternal side)
 Increasing maternal age
 Increasing parity
 Increasing body mass
 Monozygotic
 Incidence relatively
constant 3-5/100
 Largely independent
of race, heredity, age
and parity
 Assisted reproductive
therapy

9. TWIN GESTATION
 Affect ART
 Incidence of monochorionic twins with ART 1-5%
compared with the background rate of 0.4%.
 Manipulation zona pellucida may cause a defect that leads
to premature and partial hatching of the blastomeres
 Slowed movement through the fallopian tube.

10. TWIN GESTATION
 Chorionicity: # placentas
Monochorionic (1)
Dichorionic(2)
 Amnionicity: # amnions
Monoamnionitic (1)
Diamnionitic(2)

11. Twin Gestation
 Dizygotic
 Diamnionitic
 Dichorionic
 Two complete placental units
are produced, each composed
of an amnion and a chorion.
 The placentas themselves may
be separate or fused.
 The dividing membrane will
always consist of four layers.

12. TWIN GESTATION
 Monozygotic
 # placentas depends on the time at which twin
division occurs.
 If division of the zygote occurs in the first 3
days, two complete placental units will be
formed and the dividing membrane will contain
two amnion and two chorion layers, just as with
DZ.
 At about day 3, the syncytiocytotrophoblast
cells, which will give rise to the chorion, begin
to differentiate from the periphery of the
blastocyst.
 If embryonic division occurs between days 3
and 8, the placentation will be a single chorion
that has now already differentiated and two
amnions that have not yet begun to form.

13. TWIN GESTATION
 The dividing
membrane will be
thin because it
consists of only two
opposed amniotic
membranes without
the intervening
chorionic layers.

14. TWIN GESTATION
 The amnion differentiate by
about day 8.
 If embryonic division occurs
between days 8 and 13, the
twins will share a single
amnion and chorion.
 No dividing membrane
separating the fetuses.
 Allows for potentially lethal
entanglement of the umbilical
cords.

15. TWIN GESTATION
 Monochorionic/Monoamnionitic
 40% mortality (cord entanglement)
 Serial ultrasonographic assessment of fetal growth (TTTS
common).
 Daily fetal kick counts beginning at 26 weeks.
 Nonstress testing three times per week beginning at 26 weeks.
 Antenatal glucocorticoid administration at 32 weeks and
amniocentesis for fetal lung maturity.
 Elective delivery at 34 to 35 weeks if fetal lung maturity not
previously confirmed.
 Cesarean delivery usually recommended.

16. TWIN GESTATION
 Embryonic division, which
occurs after day 13, also results
in monochorionic, monoamniotic
placentation.
 There is physical attachment of
the fetuses producing conjoined
twins.
 Thoraco-omphalopagus (28%)
 Thoracopagus (18.5%)
 Omphalopagus (10%)
 Craniopagus (6%)

17. TWIN GESTATION
 TABLE 1
Placentation based on age of embryonic splitting
Age of embryonic splitting % in monozygotic twinning
< 4 days after fertilization
Dichorionic
diamniotic (33%)
4 to 8 days (stage of inner cell
mass)
Monochorionic
diamniotic (65%)
8 to 12 days (stage of embryonic
disc)
Monochorionic
monoamniotic (1%)
>13 days Conjoined twins

18. TWIN GESTATION
 Identification of Zygosity of Twins:
 DZ
 Different sex
 Two separate placentas
 4 layers in the dividing membranes (thick)
 MZ
 Dividing membrane contains only amniotic layers
 Monochorionic placenta (70%)
 Monochorionic same sex twins

19. TWIN GESTATION
 Either DZ or MZ
 If the dividing membrane has 4 layers (two amnion and
two chorion layers: diamniotic, dichorionic)
 The infants are the same sex.

20. Twin Gestation
 U/S techniques for determining chorionicity
and amnionicity
 Best U/S for determining chorionicity and
amnionicity (first trimester).
 Vaginal sonogram is preferred, due to its high
resolution.
 Early in pregnancy focus on the gestation sacs
and yolk sacs.

21. TWIN GESTATION
 Before 10 weeks’ gestation, several
sonographic findings can help determine
chorionicity and amnionicity.
(1) the number of observable gestational
sacs.
(2) the number of amniotic sacs within the
chorionic cavity.
(3) the number of yolk sacs.

22.  Number of Gestational Sacs
.
 Each gestational sac forms its own
placenta and chorion.
 Thus, the presence of 2 gestational
sacs implies a dichorionic
pregnancy.
 Single gestational sac a
monochorionic placenta.
TWIN GESTATION

23. TWIN GESTATION
 Number of Amniotic Sacs Within the
Chorionic Cavity
 In diamniotic twins, separate and distinct
amnions may be visible on ultrasound.
 The amnion grows outward from the
embryonic disk, and before 10 weeks the
separate amnions of a diamniotic
pregnancy will not have enlarged
sufficiently to contact each other and
create the inter-twin septum.
 Each single amnion is extremely thin
and delicate and endovaginal imaging is
often successful in differentiating
separate amnions.

24. Twin Gestation Amnionicity: # yolk
sac number
 The number of yolk sacs
present is equal to the
number of amnions.
 If two yolk sacs, it's
considered a diamniotic
gestation,
 If only one yolk sac is
seen, the gestation is
monoamniotic.

25. Twin Gestation
Second Trimester:
 Fetal sex visualization
 Separate placentas
 Thickness membrane layers
 "lambda" or "twin peak" sign or T-sign

26. Twin Gestation
 Membrane thickness and
chorionicity.
 In dichorionic diamniotic
pregnancies, the membranes
dividing the two amniotic cavities
is thick (>2mm)consist of two
layers of chorion and two layers
of amnion, in contrast.
 Monochorionic diamniotic
pregnancies,the dividing
membranes consist of two layers,
the dividing membrane will be
thinner in monochorionic twin
pregnancies (<2 mm )

27. Twin Gestation
 Lambda or twin peak sign
 In 1981, Bessis and Papiernik
reported that a projection of
placental tissue into the intertwin
membrane could be imaged in 20
of 24 dichorionic twin
pregnancies and in none of six
monochorionic pregnancies
 They coined the descriptive term,
"lambda" sign, for this finding,
which roughly 10 years later
again came to prominence as the
"twin peak" sign
 Best seen in the second trimester

28. TWIN GESTATION
 T-sign:
 Monochorionic gestation.
 The membrane has a flat
interface with the single
placenta.

29. TWIN GESTATION

30. TWIN GESTATION
 Vanishing Twin Syndrome
 Reabsorption of one twin early in pregnancy.
 Asymptomatic.
 5% of all patients with first-trimester bleeding may be
experiencing a vanishing twin.
 Prognosis for the surviving twin is excellent when silent
reabsorption occurs in the first trimester.

31. TWIN GESTATION
 Fetal Risk
 Placental abruption
 Stillbirth/Neonatal death
 IUGR
 Cord accidents
 Congenital anomalies
 Umbilical Cord Prolapse
 Fetal Malpresentation
 TTTS and TRAP (monochorionic)

32. TWIN GESTATION
 Maternal complications:
 Anemia
 Hyperemesis
 Gestational diabetes
 PTL/PTD
 Pre-eclampsia
 Hypertension
 Antepartum/post partum hemorrage
 Polyhydramnios
 UTI

33. TWIN GESTATION
 Acute fatty liver, which is marked by
severe coagulopathy
hypoglycemia
hyperammonemia,
 Can lead to fetal or maternal death.
 Postpartum period can be complicated by pancreatitis or
diabetes insipidus or both.

34. TWIN GESTATION
 Management
 Maternal weight gains of 24 lb by 24 weeks and overall
weight gains of 40 to 45 lb.
 Increase to 3,000 kcal/d.
 Iron (60 mg per day) and folic acid. (1 mg per day)
 Reduce activity and increase rest.
 Consider work restrictions especially after 28 weeks.

35. TWIN GESTATION
 Clinic visits at least every 2 weeks after 24 week.
 Fetal Movement Count daily after 32 weeks.
 Obstetric Ultrasound every 4-6 weeks after diagnosis
Assess for Placenta Previa
Assess Fetal Growth, r/o discordance
 Bi-weekly-Weekly Nonstress Test after 32 weeks
Assess fetal well-being
Predict cord compression

36. TWIN GESTATION
 Interpertation of Multiple Marker Screening:
 Have a decreased sensitivity for aneuploidy and a higher
false-positive rate compared with its use in singletons.
 Down syndrome detection rates in both first and second
trimester serum screening is about 52% for twins with a
5% screen positive rate.
 Suggested to use first-trimester nuchal translucency (NT)
measurement between 10 and 14 weeks to evaluate
aneuploidy.

37. TWIN GESTATION
 Timing of Delivery
 The lowest fetal death rate per 1,000 singleton conceptions was
0.9 at 3,700 to 4,000 g between 40 to 41 weeks.
 The lowest fetal death rate for twins was 3.3 per 1,000
conceptions at 2,500 to 2,800 g at 36 to 37 weeks gestation.
 The incidence of both stillbirth and early neonatal death
gradually declined until 37 to 38 weeks gestation for multiples
and increased thereafter.
 By 38 weeks gestation, asymmetric growth restriction is present
in almost half of twin pregnancies.
 Available data do not support the prolongation of a twin
gestation past 38 weeks.

38. TWIN GESTATION
 Intrapartum
 When vaginal birth is attempted, the delivery room should
be doubly set up for possible emergency cesarean,
including immediate availability of anesthesia and
neonatal services.
 Intrapartum ultrasonic scanning capability.
 Uterotonics available.
 Availability of blood and blood products.

39. Twin Gestation
 Presentation
 First twin presents vertex: 75%
 Both twins vertex: 45%
 One twin vertex, one twin Breech 37%
 Both twins Breech 10%

40. TWIN GESTATION
 Twin A vertex, twin B vertex
 Twin A vertex, twin B nonvertex
 Twin A nonvertex.

41. TWIN GESTATION
 Twin A Vertex/Twin B Vertex (40%)
 More than 80% of vertex/vertex-presenting twin gestations are
successfully delivered vaginally.
 The presentation of the second twin should be reconfirmed following
delivery of the first as a change in the presentation may occur in 10%
to 20% of cases.
 There is no evidence that perinatal outcomes for VLBW (<1500 gm)
twins are improved by cesarean delivery.
 Vaginal delivery is associated with a lesser degree of respiratory
distress and pulmonary disease in the neonatal period.
 Nor is there evidence to support the need for a cesarean based on
discordance in the size of the twins, even if twin B is substantially
larger than twin A.

42. TWIN GESTATION
 Twin A Vertex/Twin B Nonvertex (40%)
 Vaginal delivery of the nonvertex second twin by breech
extraction appears to be the best approach for infants over 1,500
g.
 Most clinicians would not recommend attempted breech
extraction if the second twin was anticipated to be significantly
larger (>500 g) than the presenting twin.
 Recommendations for route of delivery for a nonvertex twin B
whose birth weight is estimated to be less than 1,500 g is not so
clear, literature mixed.
 External cephalic version for the nonvertex second twin after
delivery is an option.

43. TWIN GESTATION
 Twin A Nonvertex (20%)
 C/S recommended
 Possibility of interlocking
 Breech twin A is free to extend
its head during labor as a result
of the space created by twin B
with increased risk cervical
spine injury.

44. TWIN GESTATION
 OBJECTIVES: To assess neonatal morbidity in twin pregnancy according to
the planned mode of delivery.
 METHODS: A retrospective cohort study of 758 consecutive sets of twins
born after 35 weeks of gestation with a cephalic-presenting first twin was
undertaken in a level III maternity unit.
 The primary outcome was a composite measure of neonatal mortality and
morbidity, including pH less than 7.0, 5-minute Apgar score less than 4,
neonatal intensive care unit transfer more than 4 days, pneumothorax, and
fracture.
 Neonatal Outcomes of Twin Pregnancy According to the Planned Mode of Delivery; Schmitz, Thomas
MD,,
Carnavalet, Céline de Carné MD,

45. TWIN GESTATION
 RESULTS: Vaginal or cesarean delivery was planned for 657
(86.7%) and 101 (13.3%) women, respectively.
 Among planned vaginal deliveries:
 515 (78.4%) patients delivered both twins vaginally
 139 (21.1%) had a cesarean delivery during labor
 3 (0.5%) had cesarean delivery for the second twin.
 Neonatal Outcomes of Twin Pregnancy According to the Planned Mode of Delivery; Schmitz, Thomas
MD,,
Carnavalet, Céline de Carné MD,

46. TWIN GESTATION
 After vaginal birth of the first twin, the mean intertwin delivery interval
was 4.9±3.2 minutes.
 Excluding pregnancy complications, the neonatal composite morbidity for
the second twin did not differ between planned cesarean and planned
vaginal delivery (5.0% compared with 4.7%)
 Neonatal composite morbidity of first twins did not differ between groups.
 CONCLUSION: For twin gestations with a cephalic-presenting first twin,
planned vaginal delivery after 35 weeks of gestation in selected women
remains a safe option in centers used to active management of the second
twin delivery.
 Neonatal Outcomes of Twin Pregnancy According to the Planned Mode of Delivery; Schmitz, Thomas MD,,
Carnavalet,
Céline de Carné MD,

47. Twin Gestations
 Other complications
 IUFD of one twin
 Twin-Twin Transfusion Syndrome (TTTS)
 TRAP (Twin reversed arterial perfusion
syndrome)
 Delayed interval delivery

48. TWIN GESTATION
 IUFD of One Twin
 Single fetal demise occurs in 2% to 5% of twin gestations (3-4X
increase with monochorionic gestations).
 When death of one fetus occurs in a dichorionic gestation, the
risk to the surviving co-twin is minimal, although higher rates of
preterm labor or PPROM.
 Monochorionic gestations deliver soon as fetal maturity
 25% mortality rate
 “acute intertwin transfusion syndrome.”
 5% to 25% of the surviving monochorionic twins have ischemic
end-organ injury (heart,kidneys brain), most frequently
neurologic (cortical necrosis).

49. Twin Gestation
 Twin-to-twin transfusion syndrome (TTTS)
 Complicates about 15% of monochorionic twin gestations
and is responsible for 17% of the perinatal mortality in
multifetal gestations.
 Results from a shared placenta,in which deep vascular
anastomoses develop between their circulations.

50. TWIN GESTATION
 The donor twin or “pump”
twin bleeds into the
circulation of a recipient twin.
 The donor twin become
anemic, hypovolemic,
hypoxic, oligohydramnios
and IUGR.
 Ischemic organ damage
involving the brain, kidneys,
or bowel.
 Can fix against the intertwing
membrane “stuck twin”

51. TWIN GESTATION
 The recipient twin
becomes volume
overloaded,
polycythaemia, polyuric
polyhydramnios and
hydrops.

52. Twin Gestation
 Sonographic features
 Marked size disparity in sixe fetuses,
discordance in size equal or over 20%.
 Disparity in size between the two amniotic sacs.
 Disparity in size of the umbilical cords.
 A single placenta.
 Abnormal Doppler S/D ratio
 Hydrops or evidence of congestive heart failure

53. TWIN GESTATION
 Prognosis
 When the disease manifests during the second trimester
there is a high risk of perinatal morbidity and mortality.
 Intrauterine hypoxia, preterm delivery and death of the
fetus (usually the donor) with subsequent death or
hypoxic-ischemic sequelae in the surviving twin (5-10%
develop neurological sequale).

54. TWIN GESTATION
 Treatments which have been advocated include digoxin,
serial amnioreduction, prostaglandin inhibitors, “give and
take” transfusion, selective fetocide, laser ablation, and
septostomy.
 The length of this list demonstrates how elusive development
of optimal therapy has proven.
 Milder cases are treated with amnioreduction/septostomy, and
more severe with laser or fetocide.

55. TWIN GESTATION
 OBJECTIVE: The objective of the study was to review current
controversy on laser therapy (LT) vs serial amnioreduction (SA)
performed for twin-twin transfusion syndrome (TTTS).
 STUDY DESIGN: A search in PubMed from 1997–2007 was
performed.
 Inclusion criteria were diamniotic monochorionic pregnancy, TTTS
diagnosed with standard parameters well defined.
 Diagnostic criterion for TTTS: discordance of amniotic fluid in the 2
sacs: maximal vertical pocket 8 cm or greater in the recipient's cavity
and 2 cm or less in the donor's cavity.
 Laser therapy and serial amnioreduction as treatment for twin-twin transfusion syndrome: a metaanalysis and review
of literature

56. TWIN GESTATION
 RESULTS:
 Ten articles provided 611 cases of TTTS (LT: 70%; SA: 30%) and
included 4 studies comparing the 2 treatments (395 cases: LT, 58%;
SA, 42%).
 Fetuses undergoing LT were more likely to survive than fetuses
undergoing SA.
Laser therapy and serial amnioreduction as treatment for twin-twin transfusion syndrome: a metaanalysis and review of
literature
 Other studies:
 Comparison of treatments suggests that laser leads to more single
survivors and amnioreduction more double survivors.
 Perinatal survival rates of <20% without treatment have improved to
>50% with modern treatments.

57. TWIN GESTATION TRAP: Twin reversed arterial perfusion
syndrome (TRAP)
 Prevalence: 0.3:10,000 pregnancies, 1%
monozygotic twin pregnancies.
 Definition: A complication of monozygotic
twin pregnancies in which one fetus
develops normally (pump twin) and the
second twin (recipient twin) demonstrates
cardiac maldevelopment ranging from
complete absence of heart tissue to some
formation of rudimentary myocardia and
gross anomalies including absent head and
extremities.
 Pump twin develops congestive heart failure
ascites, pleural effusions, poly-hydramnios,
skin edema.

58. TWIN GESTATION
 Extremely poor prognosos
 Various treatment modalities are based on
the premise of interrupting vascular
connections.
 Intrafetal radiofrequency ablation (RFA

59. TWIN GESTATION
 Objective: The objective of the study was to review perinatal
outcomes in pregnancies treated with intrafetal radiofrequency
ablation (RFA) for twin reversed arterial perfusion (TRAP).
 Study Design: Perinatal outcome data from a quaternary care referral
center were abstracted from a chart review of pregnancies with TRAP
sequence treated in the midtrimester with umbilical cord RFA of the
perfused twin.
 Intrafetal radiofrequency ablation for twin reversed arterial perfusion (TRAP): a single-center experience.
Livingston, Jeffrey C. MD; Lim, Foong-Yen MD; Polzin, William MD; Mason, Jennifer RN; Crombleholme,
Timothy M. MD

60. TWIN GESTATION
 Results:
 Twenty-one pregnancies with TRAP sequence were evaluated.
 Twelve of 13 pump twins treated with RFA (94%) survived to 30
days of life.
 The average gestational age at birth was 37 weeks (range 26–39
weeks).
 Conclusion: Primary therapy with RFA is a successful modality for
pregnancies complicated by TRAP sequence.
 Intrafetal radiofrequency ablation for twin reversed arterial perfusion (TRAP): a single-center experience.
Livingston, Jeffrey C. MD; Lim, Foong-Yen MD; Polzin, William MD; Mason, Jennifer RN; Crombleholme,
Timothy M. MD

61. TWIN GESTATION
 Delayed interval delivery
 Diamniotic, dichorionic twin gestation where the loss of
the presenting fetus is the consequence of extrusion
following either PPROM or true cervical incompetence.
 Adjunctive rescue cerclage appears to offer a better
chance of greatly prolonging the interval between
deliveries.
 Aggressive perioperative tocolysis and broad-spectrum
antibiotic coverage after delivery of the previable fetus.
 Perioperative indomethacin for prophylactic tocolysis.

62. TWIN GESTATION
 Specific pathogens such as gonorrhea, chlamydia, and
group B streptococci should be identified and treated.
 Following delivery of the first fetus, the umbilical cord is
tied, cut short, and allowed to retract back into the uterus.
 At that point, most clinicians place a 5-mm Merseline
band using the McDonald technique as a rescue cerclage
procedure.
 Tocolytic therapy, antibiotic coverage, and hospitalized
observation are continued for variable periods of time
along with intensive maternal and fetal surveillance.

63. TWIN GESTATION
 Conclusion:
 Twin pregnancies have
higher mortality and
morbidity complications
compared to singleton
gestations.
 Require physician due
dilligence.
 May need co-management
with peri-natal consultants.
 Affect outcome for mother
and both.