Multiple gestations can be either dizygotic (fraternal) twins resulting from two separate eggs fertilized by two separate sperm or monozygotic (identical) twins from the splitting of a single fertilized egg. Risk factors for twinning include race, family history, fertility treatments, and more. Complications can be fetal like prematurity or maternal like preeclampsia. Diagnosis involves history, exam, imaging and placental/fetal examination after delivery. Management consists of increased prenatal monitoring and timing delivery based on chorionicity and any complications.

1. Multiple Gestations
“”Twins
Prepared by:
Eman Falah Hassona

2. Definition
This is a pregnancy in which more than one fetus is present.
Classification:
Dizygotic Twins (Fraternal):
66% U.S. twins
fertilization of 2 ova by 2 sperm
Monozygotic Twins (Identical)
33% U.S twins
division of 1 ovum fertilized
by same sperm

3. Risk Factors
• Dizygotic twins are most common. Identifiable risk factors include
by race, geography, family history, or ovulation induction.
• Risk of twinning is up to 10% with clomiphene citrate and up to 30%
with human menopausal gonadotropin.
•Monozygotic twins have no identifiable risk factors.

7. Conjoined twins:
Also called "Siamese" twins
Incomplete division of the embryonic
disk at day 13-15 after conception
The incidence 1: 50-100,000 births
High rate of congenital anomalies
Classification according to the anatomic location of
the incomplete splitting:
thoracopagus (anterior),pygopagus (posterior), craniopagus (cephalic), or
ischiopagus (caudal).
The majority of such twins are thoracopagus

9. Complications

10. Complications
(Fetal &maternal)
Fetal
Prematurity (MC neonatal complication)
Vanishing twin
Congenital Anomalies
Hydramnios / Oligohydramnios: TTTS
Discordant growth
Intrauterine growth retardation:
IUGR ~ 70% of multiple gestations

11. Vanishing twin:
•1st trim. spontaneous loss of one .
• or more with higher order multiples fetus.
•Higher loss rate with advancing maternal age.
•Excellent prognosis for remaining fetus(es)

12. Twin-to-twin transfusion: mechanism
Donor Recipient
Placental shunt
Chronic blood loss Chronic blood gain
Hypervolemia
Polyhydramnios
Polycythemia
Embolization
Hypertension
Cardiac failure
Hypovolemia
Anemia
Hypoxia
IUGR
Decreased renal flow
 Oligohydramnios

13. The folding of the membrane
Early stages of the stuck twin phenomenon:
folding of the membrane

14. Treatment of TTTS
Fetoscopically guided laser
Coagulation to disrupt the placental blood vessels that connect the
circulations of the two fetuses.

16. Monoamniotic twins:
Cord entanglement
Twin to twin transfusion
Mortality - up to 60%
Ultrasound surveillance and delivery ~34 weeks

17. Diagnosis

18. Diagnosis
Hx
Examination
Imaging

19. Determination of zygosity
Ultrasonographic evaluation is very helpful.
◦ Discordant fetal gender >> dizygotic gestation.
◦ Thick amnion-chorionic septum >> dizygotic twins.
◦ “peak” or inverted “V” at the base of membrane septum >>
dizygotic
◦ The dividing membrane is fairly thin >> Monozygotic
But ??
◦ These findings are not definitive.
Thus, definitive diagnosis of zygosity may require detailed
examination of the placenta after delivery.

20. Dichorionic-Diamniotic: late determination
 Unlike sex fetuses
 "Lambda" or “Y” sign
 Thick membrane (> 2mm) 3-4 layers
 Two separate placentas
Placentas may fuse (40%), but
no vascular anastamosis occurs

21. Determination of chorionicity & amnionicity:
Monochorionic-Diamniotic: late determination
Same sex fetuses
"T" sign
Thin membrane: 2 layers
Fused placenta
Interplacental vascular anastamosis > 20%

22. Determination of chorionicity & amnionicity:
Monochorionic-Monoamnionic: late determination
Same sex fetuses
No membrane seen between fetuses
Adequate fluid with free movement of both fetuses
Single placenta
Interplacental vascular anastamosis - almost always

23. Management

24. Management
Antepartum care
(1) Counsel on increased nutritional needs.
(2) Monitor for preterm labor and delivery .
Menstrual-like cramps.
Onset of new Iow-back pain.
Pelvic pressure.
Change in vaginal discharge.
(3) Monitor for pregnancy-induced hypertension.
(4) Monitor for appropriate fetal growth.
(5) Monitor for fetal well-being.

25. CHOOSING THE ROUTE OF DELIVERY

26. TIMING OF DELIVERY
Uncomplicated twin pregnancies
Dichorionic/diamniotic — delivery at 38+0 to 38+6 weeks of
gestation,
Monochorionic/diamniotic at 36+0 weeks of gestation
Complicated twin pregnancies
Monochorionic/monoamniotic
between 32+0 and 34+0 weeks of gestation.

27. References :
Kaplan lecture notes obs and gyn
Blueprint obs and gyn
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