MULTIPLE GESTATION

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MULTIPLE GESTATION
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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

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Maternal Risks

• Hyperemesis
• Anemia
• PIH
• Gestational diabetes
• Postpartum hemorrhage
• Placenta previa

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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

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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

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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

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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
DIZYGOTIC
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MONOZYGOTIC Dichorionic, Diamniotic
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MONOZYGOTIC Monochorionic, Diamniotic
Highest risk of twin-twin transfusion
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MONOZYGOTIC Monochorionic, Monoamniotic
Risks cord problems, high mortality rate
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Conjoined Twins
 

• 1/200,000 births
• Half born stillborn
• More likely female 75
• Thoracopagus most common

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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

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Vascular Anastomoses
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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 gt5 g/dl between the twins

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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

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Obstetrical Management

• Serial removal of amniotic fluid for
  polyhydramnios if gt 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

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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