computation

• EDC


  Expected Date of Delivery/Confinement
• EDC calculation


  • Using Naegele's Rule (based on LMP for women with regular menstrual period)
  • Using McDonald's Rule (based on fundic height for women with irregular menstrual period)
• Naegele's Rule


  1. Go back 3 months from LMP

  2. Add 7 days

  3. Add 1 to the year
• Naegele's Rule (if LMP is Jan 1 to Mar 24)

  1. Add 9 months

  2. Add 7 days
• McDonald's Rule


  Estimates EDC based on fundic height, used if woman has irregular menstrual periods and doesn't know LMP
• Steps in Measuring Fundic Height

  1. Empty bladder

  2. Position woman in dorsal recumbent position

  3. Consider placing pillow under right buttock

  4. Ensure examiner's hands are clean and warm

  5. Place tape measure at uppermost border of symphysis pubis, run to uppermost border of uterine fundus

  6. Locate fundus and measure height in cm
• Calculating AOG in Months using McDonald's Rule

  Fundic height (cm) x 2/7 = AOG in months
• Calculating AOG in Weeks using McDonald's Rule

  Fundic height (cm) x 8/7 = AOG in weeks
• Gestational Age


  • Calculated from first day of mother's last menstrual period, not date of conception
  • Birth normally occurs at 37-42 weeks gestation, before 37 weeks is preterm