OB: Second Trimester Biometry

1. 1

   Position patient supine with slight left tilt. Curvilinear probe, adequate gel.

2. 2

   BPD/HC: axial plane through cavum septi pellucidi, thalami, and falx. No cerebellum visible. Measure outer-to-inner for BPD, outer perimeter for HC.

3. 3

   AC: true transverse at the level of the stomach and umbilical vein junction (J-shaped). Measure outer perimeter.

4. 4

   Femur length: visualize full femoral diaphysis, perpendicular to beam. Measure diaphysis only — not cartilaginous ends.

5. 5

   Calculate EFW using Hadlock formula. Plot on growth chart and note percentile.

6. 6

   Assess amniotic fluid: measure deepest vertical pocket (DVP) or AFI (four-quadrant sum).

7. 7

   Document placental location relative to internal os. Note fetal presentation.

• BPD/HC plane (transthalamic)
• AC plane (stomach/UV junction)
• Femur length
• Placental location

• Fetal biometry parameters
• EFW percentile
• AFI/deepest pocket
• Placental position

• BPD: must visualize cavum septi pellucidi and thalami
• AC: true transverse at liver/umbilical vein junction

Standard growth curves: Hadlock 1984 for EFW; Hadlock 1982 for individual parameters.