Module 1 - GAP Theory
Module 2 - GAP Practice

4.2 Serial ultrasound biometry

  • Indications:
  • – If SFH not possible

    – If pregnancy moderate or high risk (see Module 1, Ch 3)

  • Recommended frequency: 3 weekly
  • Starting from 28 weeks to establish baseline
  • Plot EFW based on preferred formula (usually Hadlock)
  • Algorithm – see GAP guidance 17


17. Perinatal Institute. GAP Guidance 2020. https://www.perinatal.org.uk/GAPguidance.pdf