KEY FACTS
Terminology
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Membranes insert on fetal surface of placenta instead of along edge
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Edges not “tacked down” & curl away from uterine wall
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Imaging
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Edge of placenta is rolled toward center
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Amniotic fluid gets between rolled-up edge & placenta
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Turning longitudinally creates band or shelf appearance
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Edges of shelf attach to placenta
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Cord insertion may be normal or marginal (vessels on edge)
Top Differential Diagnoses
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Many things create intrauterine linear echogenicities (ILE)
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Key is to look where they attach
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Synechiae (amniotic sheets)
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From uterine scar (covered by membranes)
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Thick membrane attaches to uterine wall
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Placenta may implant on synechiae
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Amniotic bands
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From rupture of amnion
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Thin membrane entangles fetus &/or umbilical cord
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Septate uterus (uterine duplication anomaly)
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Septum is always at fundus
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Marginal placental abruption
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Placental edge is lifted because of associated hematoma
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No placental shelf
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Clinical Issues
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Excellent prognosis if partial & isolated
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↑ incidence of preterm delivery, abruption, growth restriction (if most or all of placental margin is involved)
Scanning Tips
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Look for sites of attachment whenever ILEs are seen
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Make sure fetus & cord are not involved with ILE, which would indicate amniotic bands
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Look for placental shelf when edge looks free floating
