Malformation complex characterized by varying degrees of developmental failure involving sacral and lumbar vertebrae and corresponding segments of spinal cord

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  Abnormal innervation affects lower extremity development

1st-trimester US findings

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  Short crown-rump length

  
  
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  May have increased nuchal translucency

2nd- and 3rd-trimester US findings

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  Abrupt termination of spine on longitudinal views

  
  
  
  
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    Looks as if spine has been rubbed out

  
  
  
  
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  Because of absent sacrum, iliac wings are approximated or fused (shield appearance)

  
  
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  Lower extremity contractures and muscle wasting

  
  
  
  
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    Crossed-legged tailor or Buddha pose

  
  

GI and GU anomalies common and often severe

Open neural tube defect in up to 50%

Congenital heart disease in 24%

1% of infants born to diabetic mothers have caudal regression sequence (CRS)

12-16% of infants with CRS have diabetic mothers

Clinical outcome determined by level of defect

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  Neurogenic bladder, motor deficits common in survivors

Always check for spine ossification centers in axial scan plane at level of iliac wings

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  Sacrum not well ossified until mid-2nd trimester

  
  
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  Mild cases easy to miss

Can be seen at time of nuchal translucency exam

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  Should specifically target in any diabetic mother

  
  
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  Perform transvaginal exam looking for contour abnormalities of lower spine