1. MULTIPLE GESTATION

2. Incidence Spontaneous twins ~1 in 80 pregnancies
Triplets ~1 in 8000 pregnancies
Monozygotic twins- 3 to 5 per 1000 pregnancies with uniform frequency worldwide
Dizygotic twins- variable incidence (4-50 per 1000 pregnancies) by locale, race, maternal age

3. Maternal Risks Hyperemesis Anemia PIH Gestational diabetes
Postpartum hemorrhage
Placenta previa

4. Fetal Risks Congenital anomalies Growth restriction of discordant twin
Twin-twin transfusion
Fetal demise (death of one fetus puts other at risk for DIC)
Premature delivery
2nd twin: malpresentation, in utero hypoxia,
hyaline membrane disease
Cerebral palsy

5. Unique Risk of CP in Multiple Gestation
Single fetal demise
Zygosity and chorionicity (monochorionic)
Twin-twin transfusion
Growth restriction
Embryonic death
Mode and circumstances of delivery
Fetal inflammation

6. Types of Twins Dizygotic (2/3): dichorionic (2 placentas)
if implant sites are near, placentas may fuse yet there are no vascular connections
Monozygotic (1/3): dichorionic, monochorionic, diamniotic, monoamniotic
fused or separate placentas
at risk for twin-twin transfusion

7. Most common Monochor, Diamnio Single placenta MONOZYGOTIC Rare
Monochor,Monoamnio
Single placenta
Dichor, Diamnio
Separate or fused
placenta
Monochor, Monoamnio
Fused placenta
Dichor, Diamnio
Separate placenta
Twins. (A), The most common type of monozygotic twinning, with division of the inner cell mass of the blastocyst resulting in separate amnions but a single chorion and placenta; (B), a rare form of monozygotic twinning, with complete division of the embryonic disc resulting in two embryos in a single amniotic sac with a single placenta and chorionic sac; (C), monozygotic twinning with division occurring between the two-cell and morula stages to produce identical blastocysts, resulting in separate amniotic and chorionic sacs and either separate (shown) or fused placentas; (D,E), dizygotic twinning, with (D) or without (E) fusion of the placenta and chorion.
DIZYGOTIC

8. MONOZYGOTIC: Dichorionic, Diamniotic
Due to early division

9. MONOZYGOTIC: Monochorionic, Diamniotic
Highest risk of twin-twin transfusion

10. MONOZYGOTIC : Monochorionic, Monoamniotic
Twins. (A), The most common type of monozygotic twinning, with division of the inner cell mass of the blastocyst resulting in separate amnions but a single chorion and placenta; (B), a rare form of monozygotic twinning, with complete division of the embryonic disc resulting in two embryos in a single amniotic sac with a single placenta and chorionic sac; (C), monozygotic twinning with division occurring between the two-cell and morula stages to produce identical blastocysts, resulting in separate amniotic and chorionic sacs and either separate (shown) or fused placentas; (D,E), dizygotic twinning, with (D) or without (E) fusion of the placenta and chorion.
Risks: cord problems, high mortality rate

11. Conjoined Twins 1/200,000 births Half born stillborn
Conjoined Twins
1/200,000 births
Half born stillborn
More likely female ~75%
Thoracopagus most common
Thoracopagus:connected at the upper portion of the torso, share a heart, which makes it nearly impossible to separate them and save them both. Thoracopagus twins make up about 40 percent of all conjoined cases.
Eng Bunker’s home in Surry County, NC
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12. Twin-Twin Transfusion
Placental vascular anastomoses
Occurs in only 5-15% of monochorionic, diamniotic twins despite ~85% with vascular anastomoses
Does not occur in dichorionic twins
Interestingly, does not occur in monochorionic, monoamniotic twins

13. Vascular Anastomoses

14. Twin-Twin Transfusion
Dx: discordant growth by ultrasound
Amniotic sacs and umbilical cords
Single placenta
Clinical Sxs: rapid uterine growth, changes in fetal movement, preterm labor, postnatal hemoglobin difference of >5 g/dl between the twins

15. Twin-Twin Transfusion
Recipient twin:
Polycythemia
Hypervolemia
Polyhydramnios
CHF, hydrops
Hyperbilirubinemia
High birthweight
Donor twin:
Anemia
Hypovolemia
Oligohydramnios
Hypoglycemia
“stuck twin” fetus appears stuck due to amnion adhering to fetus
Decreased urine output
Lower birthweight

16. Obstetrical Management
Serial removal of amniotic fluid for polyhydramnios if > 20 weeks gestation
Create an opening in amnion between the two fetuses to allow fluid exchange
Laser ablation of placental vascular anastomoses (high complication rate)
Selective reduction of donor twin if high risk of death for both twins

17. Prognosis Perinatal death rate is 9-11 times the rate for singletons
Monoamniotic twins have the highest mortality rate mostly because of cord entanglement
Monozygotic twins have a mortality and morbidity rate that is 2-3 times that of dizygotic twins