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MULTIPLE GESTATION. 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. Maternal Risks.
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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
Maternal Risks • Hyperemesis • Anemia • PIH • Gestational diabetes • Postpartum hemorrhage • Placenta previa
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
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
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
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
MONOZYGOTIC: Monochorionic, Diamniotic Highest risk of twin-twin transfusion
MONOZYGOTIC : Monochorionic, Monoamniotic Risks: cord problems, high mortality rate
Conjoined Twins • 1/200,000 births • Half born stillborn • More likely female ~75% • Thoracopagus most common Eng Bunker’s home in Surry County, NC Return to Famous People Home
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
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
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
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
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