Detailed extended obstetric ultrasound examination

What is a detailed extended obstetric ultrasound examination?

The detailed extended obstetric ultrasound examination involves real-time US maternal evaluation plus detailed fetal anatomic examination. This is used when there is an increased risk of fetal abnormalities. The elements included in the detailed extended obstetric ultrasound examination are more detailed themselves in comparison to those of the level II examination. For the elements of fetal anatomy that are included in a detailed extended obstetric ultrasound examination, see the below table.

Elements of Fetal Anatomy in a Detailed Extended Obstetric Ultrasound Examination

Head and neck3rd ventricle4th ventricleLateral ventriclesCerebellar lobes, vermis, cisterna magnaCorpus callosumIntegrity and shape of cranial vaultBrain parenchymaNeck
FaceProfileCoronal face (nose, lips, lens)Palate, maxilla, mandible, tongueEar position and sizeOrbits
ChestAortic archSuperior vena cava and inferior vena cava3-vessel view3-vessel and trachea viewLungsIntegrity of the diaphragmRibs
AbdomenSmall and large bowelAdrenal glandsGallbladderLiverRenal arteriesSpleenIntegrity of abdominal wall
SpineIntegrity of spine and overlying soft tissueShape and curvature
ExtremitiesNumber: architecture and positionHandsFeetDigits: number and position
PlacentaMassesPlacental cord insertionAccessory/succenturiate lobe with location of connecting vascular supply to primary placenta
BiometryCerebellar widthInner and outer orbital diametersNuchal skin thickness (15-22 weeks)HumerusUlna/radiusTibia/fibula

In addition to the fetal anatomic survey elements of a level II obstetric ultrasound examination, a detailed extended obstetric ultrasound examination usually includes:

  • • Doppler US evaluation of the umbilical artery, umbilical vein, and ductus venosus.
  • • Measurement of the fetal nasal bone length.
  • • Documentation of the fetal extremities (includes imaging the forearms and forelegs to show the radius, ulna, tibia, and fibula and detailed imaging of the hands and feet to show five digits).
  • • Cardiac outflow tracts.
  • • Fetal gender.

Other anatomy that is evaluated depends on the suspected or detected abnormalities, including:

  • • Doppler US evaluation of one or both middle cerebral arteries.
  • • Demonstration of the corpus callosum (and pericallosal artery on color flow Doppler US).
  • • Measurement of fetal external ear length.
  • • Measurement of the cerebellar width and cisterna magna anteroposterior diameter.
  • • Demonstration of the anterior maxilla and mandible on transverse views.
  • • Aortic and ductal arch views.
  • • Cardiothoracic circumference (or area) ratio.
  • • Pulmonary vein drainage to the left atrium.
  • • Fetal gallbladder.
  • • Fetal spleen.
  • • Fetal adrenal glands.
  • • Sagittal and transverse kidney images.
  • • Fetal perineum (showing anal orifice).
  • • Fetal genitalia.
  • • Measurement of long bones (all four extremities) as well as foot length.
  • • Measurement of other skeletal structures such as clavicles, scapulae, and finger lengths.

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