TWINS

1. MULTIFETAL
GESTATION

2. INTRODUCTION
• The development of two or more than two fetuses simultaneously
in a pregnant uterus is called multiple pregnancy.
• Simultaneous development of two fetuses is called twin pregnancy
and it is the most common variety of multi-fetal pregnancy.
• Other types include-
three fetuses (triplets)
four fetuses (quadruplets)
five fetuses (quintuplets)
six fetuses (sextuplets)
• Zygosity – number of originating eggs/ zygotes
• Chorionicity – number of placentas

3. INTRODUCTION
Multiple pregnancy is of two types.
• DIZYGOTIC
• MONOZYGOTIC

4. Dizygotic twins or Binovular or
Fraternal twins
• It results from fertilization of two ova which
have most probably ruptured from two
distinct graffian follicles, usually of the same
ovary or one from each ovary, by two sperms.
- fetuses bear fraternal resemblance
• most common variety
• 2/3rd (67%) of all twins are dizygotic

5. Monozygotic or Uniovular twins or
Identical twins
• It results from fertilization of a single ovum by
a single sperm and occurs in 1/3rd (33%) of all
twin pregnancies.
It can be:
• DADC
• DAMC
• MAMC
• CONJOINED TWINS/SIAMESE TWINS

6. DADC
• If the cleavage takes place at about 8 cells
stage i.e within 3 days (72 hours) after
fertilization, the resulting embryo will have
two separate or a single fused placenta, two
chorions and two amnions (dichorionic
diamniotic)
• It accounts for nearly 1/3 rd of monozygotic
twin pregnancies.

7. DAMC
• If the division occurs when the inner cell mass
is forming (4-7 days), the two embryos will
develop enclosed by a single chorion, have a
single placenta but two separate amniotic
sacs
(diamniotic monochorionic)
• It is the most common variety accounting for
about 2/3 rd of monozygotic twins.

8. MAMC
• If the splitting occurs between 8-12 days after
fertilization i.e after differentiation of amnion
there is a single amniotic cavity, single chorion
and a single placenta
(monochorionic monoamniotic)
-these account for only 1-5% of monozygotic
twins.

10. CONJOINED TWINS
(SIAMESE TWINS)
• On rare occasions when splitting occurs after
the appearance of the primitive streak i.e
after the 13 th day of fertilization, it results in
the formation of conjoined twins within a
single amnion and chorion.

12. DAYS 0-3 3-9 9-12 12-15
CLASSIFICATION DADC DAMC MAMC CONJOINT
PLACENTA
NUMBER
2 1 1 1
NUMBER OF
AMNIONS
2 2 1 1
NUMBER OF
FETUSES
2 2 2 1
PROPORTION 33% 65% 1% <1%

13. Determination of zygosity
• The most frequent method to examine the
zygosity of twins is the examination of the
placenta at birth.
• In DADC (Diamniotic-dichorionic) placenta
there is a chorionic tissue present between
two amnions.
• In MAMC (Monochorionic-diamniotic)
placenta, the septum consists of two amnion
layers without interposing chorion.

14. SUPERFETATION:
• There is fertilization of two ova released in
two different menstrual cycles.
• It requires ovulation and fertilization during
the course of an established pregnancy and
the uterine cavity is obliterated by the fusion
of the decidua capsularis to the decidua vera.
• It is yet unproven in humans.

15. SUPERFECUNDATION
• It refers to the fertilization of two ova within
the same menstrual cycle but not in
the same coitus nor necessarily by sperms
from the same male.

16. INCIDENCE AND EPIDEMIOLOGY
• The frequency of monozygotic twin births is
relatively constant throughout the world at
approximately one in 250 births and is largely
independent of race, heredity, age and parity.
• There is now evidence that the incidence of zygotic
splitting is increased following assisted reproductive
technology (ART)
• The incidence of dizygotic twinning ,however is
influenced remarkably by race, heredity, maternal age,
parity and especially fertility drugs.

17. ETIOLOGY
• The exact cause of multiple pregnancy is not known.
• There are variations in the frequency of dizygotic
twinning (varying with maternal characterstics) as
follows :
• 1.) Racial –It is more common in certain races
(Nigerians,Africans) than others (Japanese) Due to high
rate of consumption of a specific type of yam
containing natural phytoestrogen
2.)Hereditary factors especially from the maternal side
(history of twin pregnancy in mother or sister)

18. ETIOLOGY
3.) High parity (especially para 5 and above)
4.)Rising maternal age : with a peak at 37 years
(due to maximum FSH levels leading to double
ovulation )
5.)Nutrition :Higher rates (25-30%) in taller,
heavier women with increased nutritional levels

19. ETIOLOGY
• 6.) Iatrogenic
-Use of assisted reproductive techniques – the
treatment of infertility with ovulation inducing drugs or
in vitro fertilization and embryo transfer possibly due
to a minor trauma to the blastocyst.
-Ovulation induction with clomiphene or
gonadotrophins increase the chances of both
monozygotic and dizygotic twins especially the later.
-Contraception –Risk of twin pregnancy increases by
two times if the conception occurs within one month
after discontinuation of oral contraception (after using
for more than 6 months )due to sudden release of
gonadotrophins.

20. PROGNOSIS
• Twin pregnancy is a high risk pregnancy.
• Maternal mortality increases (3-7 times) in
multiple pregnancy than singleton pregnancy.
• Postpartum haemorrhage which may be due to
larger size of the uterus in twin pregnancy is the
most common cause of maternal mortality
followed by anemia and pre eclampsia
• Maternal morbidity is increased significantly due
to complications and increased incidence of
operative interference in multiple pregnancy.

21. DIAGNOSIS OF MULTIPLE PREGNANCY
• HISTORY :
-Family or past history of multiple pregnancy
especially on the maternal side.
-History of treatment of infertility with
ovulation inducing drugs like FSH plus
chorionic gonadotropins or clomiphene citrate
or use of assisted reproductive techniques
like in vitro fertilization.

22. CLINICAL FEATURES
• Due to excess of hCG hormone in multiple pregnancy
and excessive distension of uterus, minor ailments of
normal pregnancy are seen commonly.
• Increased nausea and vomitting and hyperemesis
gravidarum during early pregnancy.
• Cardio respiratory symptoms like palpitation and
dyspnea are more common in later pregnancy.
• Increased chances of swelling and varicosity of leg
and vulval veins and hemorrhoids (piles) due to
pressure of large gravid uterus.
• Excessive abdominal distension.
• Excessive fetal movements.

23. ABDOMINAL EXAMINATION
• INSPECTION
-there is excessive distension of the abdomen
PALPATION
-Symphysio fundal height of the uterus is more
than the gestational period especially in the
second half of pregnancy.
• Abdominal girth is increased (>100 cm at term)
• Uterus feels full of too many fetal parts.
• Palpation of two fetal heads or three fetal poles
is diagnostic of multiple pregnancy

24. • AUSCULTATION
Presence of two distinct fetal heart sounds at
two different areas at least 10 cm apart with
a silent area in between two independent
observers, is diagnostic of twin pregnancy,
provided the difference in heart rates is
atleast 10 beats per minute.

25. • VAGINAL EXAMINATION
Depending upon the presentation of two
fetuses, one fetal head is usually felt on
vaginal examination while the fetal head may
be higher up.
Sometimes diagnosis may not be made
before the birth of first baby.

26. ULTRASONOGRAPHY
• It is an extremely important and diagnostic modality of
first choice for multiple pregnancy.
It is useful for
-Diagnosis of multiple pregnancy as early as 10th week
of pregnancy.It can also demonstrate vanishing twin
with fetal pole in one sac and no pole in the other sac.
-Fetal viability.
-Chorionicity of the placenta
-Gestation
-Fetal anomalies
-Fetal growth monitoring( at every 3-4 weeks interval
for fetal growth restriction)

27. • -Presentation and lie of the fetuses
-Twin to twin transfusion syndrome
-amniotic fluid index of two sacs
-localization of the placenta
-fetal well being
• Chorionicity can be diagnosed ultrasonographically as
early as first trimester i.e 6 to 9 weeks.
The presence of two separate placentas and a thick
>2mm dividing membrane helps in the diagnosis of
dichorionicity
• Fetuses of opposite gender are almost always dizygotic.

28. • If a triangular projection of the placental
tissue is seen to extend beyond the chorionic
surface between the layers of the dividing
membrane, then two fused placentas are
actually present, this finding is termed as
“twin peak” sign or “lambda sign” and
indicates dichorionic placenta.

32. • Monochorionic pregnancies have a very thin
<2mm dividing membrane and magnification
reveals only two layers. this right angle
relationship between the membranes and
placenta with no apparent extension of placenta
between the dividing membrane is called
“T” sign
• Ultrasonographic evaluation of the dividing
membrane is the easiest and most accurate in the
first half of pregnancy because the fetuses are
smaller.

33. DIFFERENTIAL DIAGNOSIS
• Mistaken dates
• Hydramnios
• Fetal macrosomia
• Fibroid with pregnancy
• Ovarian tumor with pregnancy
• Ascitis with pregnancy
• Full bladder
• Hydatidiform mole
• Closely attached adnexal mass

34. COMPLICATIONS
MATERNAL MORBIDITY PERINATAL MORTALITY AND
MORBIDITY
HEART FAILURE PREMATURITY
HR,SV CEREBRAL PALSY
PRE ECLAMPSIA LEARNING DISABILITIES
GESTATIONAL DIABETES SLOW LANGUAGE DEVELOPMENT
POSTPARTUM HAEMORRHAGE BEHAVIOURAL DIFFICULTIES
PROLONGED HOSPITAL STAY CHRONIC LUNG DISEASE
NEED FOR OPERATIVE VAGINAL
DELIVERY
DEVELOPMENTAL DELAY
BLOOD TRANSFUSION SPONTANEOUS LOSS

35. PREMATURITY
• Pre term labour is the most important
complication of the multiple pregnancy and main
reason for higher perinatal mortality.
• It can be due to uterine over distension,
hydramnios , intrauterine infections with or
without premature rupture of membranes.
• It may be spontaneous or iatrogenic.
• Patients with twin to twin transfusion and those
showing a discordant fetal growth may require a
preterm delivery as soon as lung maturity is
detected.

36. • The second twin is at higher risk than the first
twin, the monozygotic twins have two and a
half times higher mortality than dizygotic
twins.

37. VANISHING TWIN
• When in a twin pregnancy one of the fetuses
aborts or gets reabsorbed within 10 weeks of
pregnancy, it is called vanishing twin.
• It is seen in upto 20-60% of spontaneous twin
conception.
• There may be little accompanying bleeding.
• It is diagnosed on ultrasound examination by
observing a viable pregnancy accompanied by
a non viable one.

40. • When a fetal death occurs during second trimester the
remains of the baby get compressed and become paper like
and flattened by pressure from the survivor
(fetus compressus or papyraceous)
• The vanishing twin can cause can problems in screening for
neural tube defects( elevated levels of alpha fetoprotein in
maternal serum and amniotic fluid) and a discrepancy in
the karyotyping.
• Monochorionic twins have higher chances of abortion.
• In the dichorionic twins spontaneous abortion and loss of
one or both twins has to be kept in mind when diagnosing
twins in very early pregnancy by transvaginal USG.

41. DISCORDANT TWINS
• Are due to unequal division of the zygote
resulting in unequal placental mass, umblical cord
abnormalities, genetic diseases ,twin to twin
transfusion or placental insufficiency.
• The difference of birth weight is 25% or more
amongst the twins (expressed as a percentage of
the larger twins weight) is termed as discordant
growth.
• The smaller twin has a higher risk of perinatal
complications, long term physical and intellectual
growth restriction and risk of death.

42. COMPLICATIONS OF
MONOCHORIONICITY
• TWIN TO TWIN TRANSFUSION SYNDROME
• SELECTIVE FETAL GROWTH RESTRICTION
• SINGLE FETAL DEMISE
• MONOAMNIOTIC TWINS
• TWIN REVERSED ARTERIAL PERFUSION/ TRAP
• CONJOINED TWINS/ SIAMESE TWINS
• FETUS IN FETU

43. COMPLICATIONS OF
MONOCHORIONICITY
• SHARED CIRCULATION
• A-A
• A-V
• V-V
• PLACENTAL VASCULAR ANASTOMOSIS AND UNEQUAL
PLACENTAL SHARING as a result of post zygotic mitotic
crossing over, non-disjunction, imprinting differences,
inactivation and expression of selected genes,
differences in telomere size, discordant cytoplasmic
segregation and X- inactivation
• Unequal division of the blastomere masses during
twining

44. TTTS
• 15%
• DONOR TWIN- HYPOVOLEMIA AND
OLIGO/ANHYDRAMNIOS
• ASSOCIATED WITH EMPTY BLADDER, GROWTH
RESTRICTION AND ABNORMAL DOPPLER
FLOW IN THE UMBILICAL ARTERY
• QUINTERO STAGING

46. TTTS
• If untreated the perinatal mortality is
extremely high (>8o%).
• Although twin to twin transfusion is usually a
gradual process ,it can happen suddenly with
the death of one twin usually the recipient
due to heart failure.
• Hence recipient twin is at greater risk of death
than the donor.

47. Single fetal demise
• Risk of neurological abnormality in monochorionic co-
twin demise is eighteen times higher than the
dichorionic co-twin demise
• Single fetal death may either occur early in pregnancy
or later as the pregnancy progresses.
• Morbidity of the surviving fetus depends to a great
extent on the chorionicity of the pregnancy.
• When one monochorionic twin dies in utero there is
25% risk of necrotic neurological lesions including
cerebral palsy and renal lesions in the survivor.
• There is high risk of intrauterine death of the healthy
co twin.

48. TWIN REVERSED ARTERIAL PERFUSION
(TRAP) SEQUENCE AND ACARDIAC
TWINNING
• It is a complication in 1 % of monochorionic
pregnancies.
• It is characterised by an acardiac twin which recieves
its blood supply via a large arterio arterial anastamosis
from a normal pump co twin.
• This results in absent or rudimentary development of
the upper body structures like head or neck. The
perinatal mortality of the pump twin is high with death
usually occuring from cardiac failure, hydrops or
polyhydramnios induced pre term delivery.

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