• Establishing an accurate date of delivery is important to:
• Determine timing of antenatal screening
• Monitor growth of the fetus
• Scrutinize timing of delivery
• Common abbreviations denoting delivery date
• EDD: Estimated date of delivery
• EDC: Estimated date of confinement
• EDB: Estimated date of birth

Naegele’s Rule

• Formula used to estimate date of delivery
• Count back 3 months and add 7 days to the last normal menstrual period (LNMP) reported by the patient
• Example: The patient states that her LNMP was April 20th
  {4th Month (April) –3 months} {20th day +7 days}
  = 1st month 27th day

The baby is estimated to be due on January 27th of the following year.

Trimesters of Pregnancy

Normally, pregnancy continues for 40 weeks or 280 days

• 1st trimester: Conception until 13 6/7 weeks’ gestation
• 2nd trimester: 14 0/7 weeks until 27 6/7 weeks’ gestation
• 3rd trimester: 28 0/7 weeks until 40 6/7 weeks’ gestation