This document discusses multiple pregnancy, including twins and higher order multiples. It covers the incidence, risks, types (dizygotic/monozygotic), complications, diagnosis and management of twin pregnancies. Key points include: - Twins account for a significant percentage of preterm births and low birthweight infants. - Determining chorionicity and zygosity is important for risk assessment and management. - Monochorionic twins carry risks of complications like twin-twin transfusion syndrome requiring specialized care. - Complications include preterm birth, growth discordance, fetal demise of one twin, and others. Careful monitoring and possible interventions may be needed.

1. Multiple Pregnancy
DR NISHMA BAJRACHARYA
FCPS RESIDENT, 1ST YEAR, KMH

2. Introduction
Two or more fertilization events
Single fertilization followed by splitting of zygote
Combination of both

3. Incidence
Global incidence: 4/1000 births
Hellin’s Law : Twins: 1/80 singleton births
Triplets: 1:802
Quadruplets: 1:803
Conjoined twins: 1 : 60,000

4. Impact
Twins account for
17% of all preterm births
24% of low birth-weight infants (<2,500 g) and
26% of very-low-birth-weight infants (<1,500 g)
(ACOG,2004)
Women with twin pregnancy are 6 times more likely to be
hospitalized with complications

5. Dizygotic / non-identical twins
(binovular , fraternal, 2 egg twins)
~ two third of twins.
fertilization of two independently released ova by two different sperm.
In all polyzygotic multiple pregnancies, each zygote develops its own amnion,
chorion and placental circulation, and hence will be polychorionic.
not true twins

7. Monozygotic twins
( uniovular, identical or single egg twins)
~One third of twins.
arise from the splitting of a single fertilized egg within the first 14 days after
fertilization.
Always same sex (Identical)
does not necessarily result in equal sharing of genetic material , so they may be
discordant for genetic mutations , or may have the same genetic disease but with
marked variability in expression.
 teratogenic event

10. Etiology
Maternal age
Race and heredity : Black race
 Parity: Increasing parity (2.7% in 4th pregnancy)
 Heredity
 Pituitary Gonadotropin
 ART:
Ovulation induction with FSH and gonadotropin /chlomiphine
Greater the number of embryos transfered, the greater the risk of
multiple pregnancy

11. Determination of zygosity/ chorionicity
Chorionicity can be identified in the first trimester with sonography
Before 10 weeks sonographic findings to determine chorionicity.
Number of
1.gestational sacs
2.amniotic sacs within the chorionic cavity
3.yolk sacs.

12. 1. Number of Gestational Sacs
Each gestational sac forms its own placenta
and chorion:
2 gestational sacs: DC twin
1 gestational sac with 2 identified
heartbeats: MC twin

13. 2. Number of Amniotic Sacs Within the Chorionic Cavity
Diamniotic twins: separate and distinct amnions
before 10w the separate amnions of a diamniotic pregnancy will not have
enlarged sufficiently to contact each other and create the inter-twin septum.
TAS: Each single amnion is extremely thin and delicate: very difficult to see
TVS: often successful in differentiating separate amnions.

14. 3. Number of Yolk Sacs
2 yolk sacs are seen in the extra-embryonal
coelom: diamniotic
1 yolk sac
--in most cases indicate monoamniotic twins
-- when there are dual embryos: a follow-up 1st T
scan to definitively assign amnionicity.

16. After 10 weeks
These sonographic signs are no longer present: gestational sacs are no
longer distinctly separable, and the inter-twin membrane is formed.
Findings:
1.Genitalia
2. Placental number
3. Chorionic peak sign
4. Membrane characteristics.

17. Number of Distinct Placentas
1 placental mass: MC
2 distinct, separate placentas: DC
Presence or Absence of the Chorionic Peak
(twin peak or lambda sign)
Projecting zone of tissue of similar
echotexture to the placenta
Triangular in cross-section and wider at the
chorionic surface of the placenta, extending
into, and tapering to a point within, the inter
twin membrane.
 Most often identifies DC
MC: absence of the twin peak sign.

18. Dichorionic Twins (Two placentas) Lambda sign Monochorionic Twins (One placenta) T sign

19. Inter-Twin Membrane Characteristics
DC : 2 layers of amnion and 2 layers of chorion.
Thicker > 2 mm
more reflective
MC: ≤ 2mm
In 2nd T: Number of membranes may be counted, and if there are > 2, then
dichorionicity is strongly suggested

20. Dichorionic Diamniotic twin: a triangular projection of
chorionic tissue emanating from fused dichorionic
placentas and extending between layers of the intertwin
membrane.
Dichorionic twin in the first trimester: a thick inter twin
membrane

21. Monochorionic Twins thin intertwin membrane
Monochorionic Twins
(One placenta)
T sign

22. Pregnancy complications
2 to3 fold increased than singletons
Threatened and spontaneous abortions (vanishing twin) 7.3 % risk in multiple
pregnancy versus 0.9 % in singleton (Joo, 2012)
Hyperemesis
Severe anemia
Hypertensive disorders of pregnancy: 3 to 4 fold increase
Gestational diabetes
Antepartum hemorrhage: abruption
Preterm premature rupture of the membranes
Operative delivery
PPH : 3-4 fold increase
Increased maternal mortality

23. Fetal complications
Congenital Malformations- 406/10000 in twins versus 238/10000 singletons
(Glinianaia and associates, 2008)
Low birthweight- due to restricted fetal growth and preterm delivery
Preterm birth
Monochorionic pregnancy complications
Perinatal asphyxia
Fetal death, Cord accidents
Increased perinatal mortality

24. Unique fetal complications
Monoamniotic twins- 1 in 20 monochorionic twins are
monoamniotic
Associated with high fetal death rate from cord entanglement,
congenital anomalies, preterm birth, or twin- twin transfusion
syndrome
Diamniotic twins can become monoamniotic if the dividing
membrane ruptures

25. Aberrant twinning mechanisms

26. Conjoined twins

27. External parasitic twins- grossly defective fetus or merely fetal parts attached
externally to a relatively normal twin
Believed to result from demise of the defective twin with its surviving tissues
attached to and vascularized by its normal twin
Fetus in fetu- early in development, one embryo may be enfolded within its twin
Classically vertebral or axial bones are found in these fetiform mases, supported
by their host by a few large parasitic vessels

28. Monochorionic twins with vascular
anastomoses
Two amniotic sacs and a common surrounding chorion
 anatomical sharing of the two fetal circulations through
anastomoses of placental arteries and veins
Artery to artery anastomoses are most common and are identified on
the chorionic surface of the placenta- 75%
Vein to vein and artery to vein– approx. 50%

29. Deep artery to vein connections can extend from capillary bed of a
given villus, creating a common villous compartment or third
circulation
Depending on the degree to which they are hemodynamically
balanced, severity occurs
With significant pressure or flow gradients, a shunt will develop
between fetuses
Chorioinic feto fetal transfusion result in several clinical syndromes

30. Twin-Twin Transfusion syndrome
5 – 17 % of monochorionic twin
Mortality irrespective of
gestational age is 60-70%
Mechanism: deep A-V vascular
anastomosis

31. Blood is transfused from donor twin to its recipient sibling – donor is anemic and
growth may be restricted
Recipient becomes polycythemic, with circulatory overload and may manifest as
hydrops
Classic TTTS results from unidirectional flow through AV anastomoses
Deoxygenated blood from donor placental artery- pumped into a cotyledon shared
by recipient. Once oxygen exchange is completed in the chorionic villus,
oxygenated blood leaves the cotyledon via a placental vein of the recipient twin

32. Clinically important TTTS is frequently
chronic, results from significant volume
differences
Presents in mid pregnancy, donor fetus-
oliguric due to decreased renal perfusion –
develops oligohydramnios
Recipient- polyhydramnios
Stuck twin, polyhydramnios-
oligohydramnios – syndrome (poly-oli)

33. Diagnosis
Society for maternal- fetal medicine (2013)
Two criteria- 1.presence of a monochorionic diamniotic pregnancy
2. Hydramnios defined if the largest vertical pocket > 8 cm in one twin and
oligohydramnios < 2cm in the other twin.
Quintero staging:
Stage 1 – Oligo/poly sequence and bladder seen in donor twin, normal Doppler
studies
Stage 2 - Oligo/poly sequence; donor bladder not seen; normal Doppler studies.

34. Stage 3 - Oligo/poly sequence; donor bladder not seen; Doppler with at least one
of the following alterations:
 Absent or reversed diastolic flow in the umbilical artery of the donor twin
Reversed flow in the ductus venosus of the donor twin
Pulsatile flow in the umbilical vein of the recipient twin.
Stage 4 – fetal hydops in any of the twins
Stage 5 – Death of one or both twins.

35. Management and Prognosis
Related to Quintero staging and gestational age at presentation
> 3/4 of stage 1 cases- remains stable and regress without
intervention
Perinatal loss rate of 70-100 % of stage 3 or more without
intervention
Therapies- amnioreduction, laser ablation of vascular anastomoses,
selective feticide, septostomy

36. Recommendations by RCOG
TTTS should be managed in conjunction with fetal medicine centres with
recourse to specialist expertise and treatment in supraregional centres.
TTTS presenting before 26 weeks of gestation should be treated by fetoscopic
laser ablation rather than amnioreduction or septostomy.
Weekly ultrasound assessment (including examination of the fetal brain, heart
and limbs) and serial measurements of UAPI, MCA- PSV and ductus venosus
Doppler velocities should be performed. After 2 weeks post treatment, the
ultrasound interval can be increased to every 2 weeks with documentation of
adequate fetal growth (by calculating EFW).
In treated TTTS pregnancies, ultrasound examination of the fetal heart should
be performed by the fetal medicine specialist to exclude functional heart
anomalies.

37. Serial amnioreduction
Laser photocoagulation of placental vascular
anastamosis

38. septostomy Selective feticide

39. Twin Anemia Polycythemia Sequence
(TAPS)
3-5 % monochorionic pregnancies
13% after laser photocoagulation
Significant hemoglobin differences between donor and recipient twins without
the discrepancies in amniotic fluid volumes
Diagnosis- MCA peak systolic velocity (PSV) > 1.5 mutiples of median in
donor and <1.0 multiples of median in recipient twin
Spontaneous TAPS usually occurs after 26 weeks and iatrogenic TAPS within 5
weeks after the procedure.

40. Twin Reversed Arterial Perfusion
(TRAP) Sequence
Aka acardiac twin
Most serious complication of monochorionic multifetal gestation
1 in 35,000 pregnancies
Normally formed donor twin with features of heart failure and
recipient twin that lacks a heart and other structures.
Hypothesis- caused by a large artery to artery placental shunt, also
accompanied by vein to vein shunt.

41. Discordant growth of twin fetuses
15 % of twin gestation
Diagnosis- sonographic fetal biometry to compute the estimated
weight for each twin
% discordancy= (wt of larger twin- wt of smaller twin)/ wt of larger
twin (20% or more)
AC measurements differ more than 20mm
Weight discordancy > 25-30 % predicts an adverse perinatal
outcome- such as respiratory distress, intraventricular hemorrhage,
seizures, sepsis etc

42. Selective growth reduction (sGR)
sGR (growth discordance of > 20%) --Approximately 10–15% of
monochorionic twins
Cause- unequal placental sharing where one fetus gets blood from major
placental territory than the other
Stage I- Growth discordance but positive diastolic velocities in both fetal
umbilical arteries.
Stage II- Growth discordance with persistent absent or reversed end-
diastolic velocities (AREDV) in one or both fetuses.
Stage III- Growth discordance with intermittent absent or reversed end-
diastolic flow in a cyclical pattern(iAREDV)

43. Recommendations by RCOG
sGR in monochorionic twins requires evaluation in a fetal medicine centre.
In cases of early-onset sGR in association with poor fetal growth velocity and
abnormal umbilical artery Doppler assessments, selective reduction may be
considered an option.
surveillance of fetal growth should be undertaken at least every 2 weeks with fetal
Doppler assessment (by umbilical artery and middle cerebral artery pulsatility index,
and peak systolic velocity)
Clinicians should be aware that there is a longer ‘latency period’ between diagnosis
and delivery in monochorionic twins complicated by sGR compared with growth
restriction in dichorionic twin pregnancy or singleton pregnancy.

44. In type I sGR, planned delivery should be considered by 34–36 weeks of
gestation if there is satisfactory fetal growth velocity and normal umbilical artery
Doppler waveforms.
In type II and III sGR, delivery should be planned by 32 weeks of gestation,
unless fetal growth velocity is significantly abnormal or there is worsening of the
fetal Doppler assessment.

45. Fetal demise
More in monochorionic twins
Death of one fetus- early in pregnancy- vanishing twin
Fetal death in a slightly more advanced gestation sometimes- can go unnoticed, and
during delivery- normal appearing live infant along with dead fetus, compressed-
fetus compressus
Flattened remarkably through desiccation -fetus papyraceus
Management- decision should be based on gestational age, cause of death and risk
to surviving fetus

46. Vanishing twin in first trimester is harmless
If loss occurs in 2nd trimester, the risk of death and damage to survivor is limited
to monochorionic twin, (due to vascular anastomoses)
Single fetal death during late second and early third trimester presents the
greatest risk to the surviving twin.
Risk of preterm birth is increased
After a single fetal death in a monochorionic pregnancy, the risks to the
surviving twin of death or neurological abnormality are 15% and 26%,
respectively.

47. Prenatal care and antepartum
management
All women with a twin pregnancy should be offered an ultrasound examination
between 11+0 weeks and 13+6 weeks of gestation (crown–rump length 45–84
mm) to assess fetal viability, gestational age and chorionicity, and to exclude
major congenital malformations.
Chorionicity should be determined at the time the twin pregnancy is detected by
ultrasound based upon the number of placental masses, the appearance of the
membrane attachment to the placenta and the membrane thickness. This scan is
best performed before 14 weeks of gestation.

48. Women with monochorionic twins who wish to have aneuploidy screening
should be offered nuchal translucency measurements in conjunction with first
trimester serum markers (combined screening test) at 11+0 weeks to 13+6 weeks
of gestation
In women with monochorionic twin pregnancies who ‘miss’ or who have
unsuccessful first trimester screening for aneuploidy, second trimester screening
by the quadruple test should be offered.
All monochorionic twins should undergo a routine detailed ultrasound scan
between 18 and 20+6 weeks of gestation which includes extended views of the
fetal heart anatomy.

49. Fetal ultrasound assessment should take place every 2 weeks in uncomplicated
monochorionic pregnancies from 16+0 weeks onwards until delivery.
At every ultrasound examination, liquor volume in each of the amniotic sacs
should be assessed and a deepest vertical pocket (DVP) depth measured and
recorded, as well as the umbilical artery pulsatility index (UAPI). Fetal bladders
should also be visualised.
Although first presentation of TTTS is rare after 26+0 weeks of gestation, it can
occur and therefore, scans should be performed at 2-weekly intervals in
uncomplicated monochorionic twins until delivery
From 16+0 weeks of gestation, fetal biometry should be used to calculate an
EFW and the difference in EFW calculated and documented. As the risk of sGR
extends to delivery, this should be performed at 2-weekly intervals until delivery.

50. Prediction of preterm birth
Cervical Length Measurement by Ultrasonography
<25 mm at 24 wks-best predictor for preterm birth
>35 mm at 24 wks-low risk of preterm birth

51. Prevention of preterm birth?
Routine Hospitalization
retrospective study have shown that bed rest in the hospital does not prolong twin gestation
Prophylactic Cerclage
cerclage did not prolong gestation or improve perinatal outcome
Restriction of Activities and Rest at Home
it has not been evaluated in a prospective randomized manner.
Progesterone therapy-
Weekly injections of 17 a hydroxyprogesterone caproate (17 OHPC) is not shown to be
effective for multifetal gestations.
Vaginal progesterone therapy (Micronized progesterone) no certain benefit

52. Tocolytics
trials showed no consistent effect on preterm birth, birth weight, or neonatal
mortality.
Corticosteroids
recommends that all women in preterm labor who have no contraindications to
steroid use be given one course of steroids, regardless of the number of fetuses

53. Labor and Delivery
Timing of delivery of twins should be decided when the benefit of prolonging
the pregnancy is outweighed the risk of still birth
Perinatal mortality of twins starts to become significantly high after 38 weeks
Uncomplicated dichorionic twins – managed expectantly and delivery can be
around 38 weeks
In cases of prematurity and discordant fetal well being exists, timing of delivery
should be based on parameters of healthy twin.
Uncomplicated monochorionic twins- delivery at around 37 weeks
In case of discordant fetal well being or an anomaly, timing of delivery should
be based on the condition of compromise fetus.

54. Mode of Delivery
Cephalic- cephalic presentation- vaginal delivery preferred,
RCT by Barrett and coworkers (2013) concluded that planned cesarean delivery
does not improve neonatal outcome when both twins are cephalic
Cephalic- non cephalic presentation- controversial
Reports say- vaginal delivery of second non cephalic twins whose birthweight
<1500gm is safe
2nd twin- breech extraction of non cephalic twin, or internal podalic version of an
unengaged cephalic second twin followed by breech extraction
Following delivery of 1st twin, the presenting part of the second twin, its size, and
its relationship to the birth canal should be quickly and carefully ascertained by
combined abdominal, vaginal and at times, intrauterine examination.

55. Internal podalic version- with this maneuver, a fetus is turned into a breech
presentation using the hand placed into the uterus.
Breech extraction is considered superior to external version because less fetal
distress developed.
Breech presentation of the first twin- similar as singleton breech fetus- cesarean
delivery is preferred
Locked twins- first fetus breech and second cephalic, breech of the first twin
descends through the birth canal, the chin locks between the neck and chin of the
second cephalic presenting co twin- cesarean delivery is preferred.

56. Multifetal pregnancy reduction (MFPR)
Initially used as a procedure to selectively terminate fetuses with congenital
abnormality or genetic d/o
Now, usage to terminate one or more fetuses of a multiple gestation pregnancy
while allowing some fetuses to remain alive
Risks associated and ethical issues related to it are still a debate.
MFPR is usually carried out through transabdominal route with USG guidance.
2-3 Meq KCL is injected to each fetus that is to be terminated into fetal thorax,
asystole should be observed for 3 minutes
Associated with 5-7 % risk of miscarriage.

57. Keys to remember
Multiple pregnancies are at increased risk of pregnancy complications that
singletons
Pregnancy outcome of multiple pregnancy is mainly determined by the chorionicity
First trimester USG is very reliable in determining accurate pregnancy dating,
chorionicity, orientation and abnormal twin gestation
Monochorionic twins should be monitored more often between 16- 24 weeks for
early diagnosis of fetal transfusion syndromes
Fetal growth of the multiple pregnancy should be monitored 4 weekly from 26-38
weeks

58. In case of suspected fetal transfusion syndrome, discordant growth >25
%, MCMA and higher order twins should be managed in specialized
centers
Uncomplicated DC twins should be delivered at 38 weeks,
Uncomplicated monochorionic twins- delivery at around 37 weeks
Mode of delivery is decided by presentation of presenting twin, gestation
of delivery, chorionicity and fetal well being at the time of delivery
MFPR is an option to improve pregnancy outcome in higher order
multiples.

59. References
Fernando Arias, Shirish, Amarnath. Multifetal gestation, High
risk pregnancy and delivery. 4th edition
 RCOG Green-top Guideline No. 51, November, 2016
Cunningham, Levono, Bloom, H Auth, Rouse,Sponge. Multifetal
Pregnancy Williams obstetrics; 24th edition
ACOG practice bulletin. Clinical management guidelines for
Obstetrician–Gynecologists.Number 56, October 2004

60. Thank you