2. OBJECTIVES:
• Definition.
• Incidence and epidemiology.
• Clinical characteristics.
• Classification.
• Diagnosis.
• Complications.
• Abnormalities of the twinning process.
• Management.
3. DEFINITION:
• Any pregnancy which two or more embryos or
fetuses present in the uterus at same time.
• It is consider as a complication of pregnancy due
to ;
▫ The mean gestational age of delivery of twins is
approximately 36w.
▫ The perinatal mortality &morbidity increase.
4. Terminology vs. number
Singletons one fetus
Twins tow fetuses.
Triplets three fetuses.
Quadruplets four fetuses.
Quintuplets five fetuses.
sextuplets six fetuses.
Septuplets seven fetuses.
5. Mean gestational age of delivery
Number of babies Weeks of Gestation
1 40 weeks
2 36 weeks
3 33 weeks
4 29 ½ weeks
6. Incidence & epidemiology
• The incidence of multiple pregnancy in US is
approximately 3% (increase annually due to ART ).
• Monozygotic twins ( approx. 4 in 1000 births ).
• Triplet pregnancies ( approx. 1 in 8000 births ).
• Multiple gestation increase morbidity & mortality
for both the mother & the fetuses.
• The perinatal mortality in the developed countries
▫ Twins = 5 – 10 % births.
▫ Triplets = 10 – 20 % births.
7. Clinical characteristics:
Multiple gestation should be suspected when ;
Uterine size is greater than expected for
gestational age.
Multiple FHRs are heard
Multiple fetal parts are felt.
hCG & serum alpha-fetoprotein levels are
elevated for gestational age.
If the pregnancy is a result of ART.
Diagnosis is confirmed by US .
8. DDx of uterus that is greater than
expected for gestational age:
1- Polyhydramnios.
2- Macrosomia.
3- Placental abruption.
4- Gestational trophoplastic disease.
5- Uterine fibroid.
6- Ovarian mass.
9. Classification
Dizygotic (>70%) Monozygotic (<30%)
Dichorionic/Diamniotic
Dichorionic/Diamniotic Monochorionic/Monoamniotic
(8%( (1%)
Monochorionic/Diamniotic
(20%)
N.B. : Placentation in higher-order multiples ( triplets, quadruplets…( follows the same
principles, except monochorionic & dichorionic may coexist.
10. Important notes:
1- Monozygotic twins having same sex & blood
group.
2- Process of formation of chorion is earlier than
formation of amnion.
3-Dizygotic twins must be dichorionic/diamniotic.
4- There is no dichorionic/ monoamniotic.
11. A- Dizygotic twins (fraternal):
Most common represents 2/3 of cases.
Fertilization of more than one egg by more than
one sperm.
Non identical ,may be of different sex.
Two chorion and two amnion.
Placenta may be separate or fused.
“each fetus is contained within a complete
amniotic-chorionic membrane “
12. Cont
The incidence of dizygotic twins is higher in ;
1. Certain families .
2. Race ;African Americans .
3. Increases with maternal age, parity, weight and
height .
4. Ovulation induction.
13.
14. B- Monzygotic twins:
Constitutes 1/3 of twins
These twins are multiple gestations resulting from
cleavage of a single, fertilized ovum.
The timing of cleavage determines the
placentation of the pregnancy.
Constant incidence .
Not affected by heredity.
Not related to induction of ovulation.
15. Time of Nature of membranes % Perinatal
cleavage mortality
0 - 72 hr diamniotic,dichorionic 8 8.9%
4 – 8 days diamniotic,monochorionic 20 25%
9-12days monoamniotic,monochorionic 1 50-60%
>13 days Conjoined twin ---- -----
16.
17.
18. Placentation in Higher-Order Multiples ;
The relationship of placentas among triplets,
quadruplets, and higher-order multiple fetuses
generally follows the same principles, except that
monochorionic and dichorionic placentation may
coexist, and placental anomalies are more frequently
found in higher-order multiples.
19. Diagnosis:
• History:
▫ Family hx of dizygotic twins.
▫ Use of fertility drugs.
▫ sensation of excessive fetal movements.
▫ Exaggerated symptoms of pregnancy (hyperemesis
gravidarum ).
• Examination:
▫ GPE ( weight gain, Pre-eclampsia signs )
▫ Abdominal examination (excessive uterine fundal
growth, and auscultation of fetal heart rates in separate
quadrants of the uterus are suggestive but not
diagnostic).
• Sonographic examination ( diagnostic )
20. Ultrasound evaluation:
• The diagnosis of multiple gestation requires a
sonographic examination demonstrating two
separate fetuses and heart activities.
• The diagnosis can be made as early as 6 weeks of
gestation.
21. DETERMINATION OF ZYGOSITY:
Very important as most of the complications occur in
monochorionic monozygotic twins.
By ;
Ultrasound : genders,numbar of placentas,
Blood groups.
HLA.
DNA analysis.
22. • During pregnancy by US :
• Very accurate in the first trimester, two sacs,
presence of thick chorion between amniotic
membrane .
• Less accurate in the second trimester the
chorion become thin and fuse with the amniotic
membrane .
• Different sex indicates dizygotic twins.
• Separate placentas indicates dizygotic twins
23. After birth ;
• By examination of the MEMBRANE,
PLACENTA,SEX , BLOOD group .
• Examination of the newborn DNA and HLA may
be needed in few cases.
24. DETERMINATION OF ZYGOSITY:
Findings Zygosity Freq.
Different genders dizygotic 30%
Two placentas,same gender dizygotic 27%
different blood groups
One placentas monozygotic 23%
Two placentas,same gender HLA & DNA analysis 20%
Same blood group
25. US
different gender same
dizygotic Monozygotic Number of
twins twins 1 placenta
2
different same
same Blood
HLA & DNA group
analysis
different
26. Septum Placental type Twin type
1- None Monochorionic/Monoamniotic monozygotic
2- Amnion only Monochorionic/Diamniotic monozygotic
3- Amnion & chorion Dichorionic/ diamniotic Dizygotic or monozygotic
4- No common septum Dichorionic/ diamniotic dizigotic
1 2 3 4
27.
28. Complications:
• A - Maternal:
▫ Antepartum
Anemia.
Miscarriage.
Preeclampsia ( 40% in twins & 60% in triplets ).
Polyhydramnios ( 5 – 8%).
PTL ( Twin account for 10% of all PTL & 25% of all preterm
perinatal deaths ).
Cervical incompetence.
Hyperemesis gravidarum.
▫ Intrapartum
CS.
▫ Postpartum
postpartum uterine atony. b/c of
post partum Hemorrhage. Over distended uterus
postpartum endometritis
33. Conjoined Twins ;
• Etiology : It result from cleavage of the embryo is
incomplete because it happen very late (after 13 days,
when the embryonic disc has completely formed).
•
• Incidence : once in 70,000 deliveries.
• Classification:
▫ Thoracopagus (antreior) “most common”.
▫ Pygopagus (posterior)
▫ Craniopagus (cephalic)
▫ Ischiopagus (caudal)
• Delivery by C.S.
35. Interplacental Vascular Anastomoses:
• It occurs almost exclusively in monochorionic
twins at a rate of 90% or more.
• Type:
▫ Arterial_artarial(most common).
▫ Arterial_venous.
▫ Venous_venous.
• Complications:
▫ Abortion.
▫ Hydramnios.
▫ Twin-twin transfusion syndrome (TTTS).
▫ Fetal malformations.
36. Twin-Twin Transfusion Syndrome ;
• Definition:
▫ 15% of monochorionic twins have domensturable
anastomosis.
▫ The presence of unbalanced anastomosis in the placenta
(typically arterial-venous connections) leads to a syndrome in
which one twin’s circulation perfuses the other Twin.
• Complication:
▫ Donor : anemic HF, hypovolemia, hypotension, anemia,
oligohydramnios, growth restriction. ( do intrauterine blood
trans fusion).
▫ Recipient : hypervolemic HF , hypervolemia, hypertension,
polyhydramnios, thrombosis, hyperviscosity,cardiomegaly,
polycythemia, hydrops fetalis. ( do repeated amnioreduction).
▫ Both: risk of demise & PTL.
37. Management of TTTs ;
If not treated death occurs in 80-100% of cases.
If extreme prematurity prevents immediate delivery,
Several interventions can be considered in view of the
high mortality associated with expectant management.
• Repeated amniocentesis from ( recipient) .
• Intrauterine transfusion of the anemic (donor) twin
is of no benefit in this condition.
• Indomethacin.
• Fetoscopy and laser ablation of communicating
vessels.
38.
39. Fetal Malformations:
• Incidence:
▫ Twice as common in twins & 4 times more common
in triplets than in singleton infants.
▫ Monozygotic > Dizygotic.
• Etiology:
▫ Usually result from arterial-arterial anastomosis.
▫ Common deformations in twins include limb
defects, plagiocephaly, facial asymmetry, and
torticollis.
▫ Acardia and twin-reversed arterial perfusion
(TRAP) “ rare but unique to multiple pregnancy”.
• Amniocentesis:
▫ If U/S shows abnormality.
41. Umbilical Cord Abnormalities:
• Absence of one umbilical artery occurs in about
3% to 4% of twins (30% of case absence of one
artery associated with other congenital
anomalies”renal agenesis” ).
• Cord entanglement ( esp. in monochorionic
monoamniotic twins ).
42. Discordant Twin Growth:
• Definition:
▫ Discrepancy of more than 20% in the estimated fetal
weights.
• Causes:
▫ TTTS.
▫ Chromosomal or structural anomalies.
▫ Discordant viral infection.
▫ Interplacental Vascular Anastomoses.
43. Specific indication C/S in Twins ;
1. monochorionic monoamniotic twins
2. Conjoined twins
3. Non vertex presentation of first twin
4. Locked twins
5. Twin-reversed arterial perfusion (TRAP)
6. Placentation in Higher-Order Multiples
7. Other obstrictic indication of C/S
44. Management:
Antepartum
• Adequate nutrition.
▫ Adequacy of maternal diet is assessed due to the increased
need for overall calories, iron, vitamins, and folate .
▫ The Institute of Medicine (IOM) recommends women with
twins gain a total of 16.0 to 20.5 kg during the pregnancy.
• More frequent prenatal visits.
• Periodic U/S assessment “ every 3-4 weeks from23weeks’
gestation “ to monitor the growth and detection of
discordant growth or TTTS.
• Fetal surveillance:
▫ Performance of NST is not indicated before 34 wks unless to
confirm IUGR or discordant growth.
▫ ( avoid CST )
• Amniocentesis. ( If indicated )
45. In case of death of one fetus is managed based on the gestational
age and condition of the surviving fetus.
1- fetal surveillance weekly measured Until evidence
2- maternal clotting profiles of fetal lung maturity in the
surviving fetus is exhibited
Delivery should be considered if :
1) Fetal lung maturity is demonstrated
2) If compromise of the remaining fetus develops
3) If evidence of disseminated intravascular coagulation in the
mother is present.
In the setting of TTTS, the death of one twin should prompt
consideration of delivery, particularly after 28 weeks, given the
high rates of embolic complications in the surviving twin.
46. Cont..
Intrapartum
• The route of delivery depends on:
▫ Presentation of the twins.
▫ Gestational age.
▫ Presence of maternal or fetal complications.
▫ Experience of obstetrician.
▫ Availability of anesthesia & neonatal intensive
care.
47. Delivery:
• Vertex/Vertex(43%):
▫ Vaginal delivery. (Successful in 70-80%of cases).
▫ Surveillance of twin B with real-time U/S.
• Vertex/Nonvertex(38%):
▫ Vaginal delivery ( better ) (in absence of discordant
growth).
▫ Either external cephalic version or podalic version
with breech extraction may be attempted.
▫ CS.
• Nonvertex Twin A(19%):
▫ CS .
49. Multiple gestation with more than
two fetuses
Most frequent cause is iatrogenic from the use of
ovulation induction agent.
Prematurity increase as the number of fetuses
increase .
1) Multifetal reduction may be offered:
Reduce the risk to the mother & the remaining
fetuses.
Performed only in the setting of dichorionic
/diamniotic gestation.
2) Selective termination:
Termination of one or more fetuses with structural or
chromosomal anomalies.
51. References
• The Johns Hopkins manual of gyencology &
obestetrics.
• Essentials of gyencology & obestetrics by
Hacker, Moore & Gambone.
• Pictures: From internet.
