Diagnostic ultrasound ( PDFDrive )

1124 PART IV Obstetric and Fetal Sonography
of the second twin, 42,67,68 which is also more likely in monochorionic
twins, and the risk is particularly high for monoamniotic
twins. 39 Ater loss of one twin, the surviving twin is at increased
risk for adverse outcome, and the risk is again associated with
chorionicity, as a result of the vascular anastomoses in a shared
placenta.
In a dichorionic gestation with a single IUFD, there is no
signiicant risk of injury to the surviving fetus, but there is an
increased rate of preterm delivery. 67 However, in monochorionic
twins with a single demise, risk of severe cerebral injury in the
survivor may be as high as 25% to 34%. 68,69 In these cases, fetofetal
hemorrhage is thought to be responsible. When the irst fetus
expires, there is a sudden drop in vascular resistance across the
placental anastomoses and blood is shunted away from the
survivor, with subsequent anemia, hypotension, and hypoperfusion
of vital organs. his mechanism has been conirmed with in
utero documentation of anemia in surviving fetuses. 17,70,71 he
developing central nervous system is at highest risk for signiicant
injury, and the consequences of the insult may not be apparent
immediately. he sonographic manifestations of cerebral ischemia
are similar to those seen in premature infants, namely, intracranial
hemorrhage, middle cerebral artery infarction, and periventricular
white matter injury with subsequent leukomalacia (Fig. 32.10).
Renal injury can result in cortical necrosis, and limb reduction
A
B
C
D
FIG. 32.10 Sequelae of Intrauterine Fetal Demise in Monochorionic Twin Gestations. (A) Axial image of the fetal head 24 hours after
amnioreduction of 1800 mL from the gestational sac of this fetus. There is an echogenic lesion inseparable from the dependent lateral ventricle
consistent with intraparenchymal hemorrhage (arrowheads). (B) Same patient as A. Postnatal head ultrasound of the same twin, day of life 1, 48
hours after amnioreduction. There is a large intraparenchymal hemorrhage on the right (arrowheads). (C) Monochorionic twin at 30 weeks’
gestational age, following an IUFD of its twin 3 weeks ago. There is new ventriculomegaly of the survivor. (D) Same patient as C, 1 week later.
Postnatal head ultrasound on day of life 3 shows cystic changes (arrowheads) in a parietal periventricular location consistent with periventricular
leukomalacia, the result of the intrauterine fetal demise 4 weeks earlier.