09/08/2026
EDD (Estimated Date of Delivery) β Nursing Quick Notes π€°π
EDD (Estimated Date of Delivery) is the estimated date on which a pregnant woman is expected to give birth. It is also called the expected date of delivery or due date.
Normal Pregnancy Duration
Approximately 40 weeks
280 days from the first day of the Last Menstrual Period (LMP)
EDD is an estimate, not a guaranteed delivery date.
How to Calculate EDD β Naegeleβs Rule
EDD = LMP + 7 days β 3 months + 1 year
Example:
LMP: 10 January 2026
7 days β 17 January 2026
β 3 months β 17 October 2025
1 year β EDD: 17 October 2026
Dating by Ultrasound
A first-trimester ultrasound provides the most accurate ultrasound estimation of gestational age and is particularly useful when:
LMP is uncertain
Menstrual cycles are irregular
LMP dating does not agree with ultrasound dating
Why is EDD Important?
Plans antenatal appointments and investigations
Helps monitor fetal growth and development
Guides timing of pregnancy screening
Helps assess preterm and post-term pregnancy
Supports planning for labour and delivery
Helps guide appropriate maternal and fetal care
Factors That Can Affect LMP-Based EDD
Irregular menstrual cycles
Uncertain LMP
Recent hormonal contraception
Breastfeeding
Variation in timing of ovulation
Key Nursing Points
Record the first day of the LMP accurately.
Calculate and document the EDD.
Confirm gestational dating with the dating ultrasound when appropriate.
Monitor pregnancy according to gestational age.
Explain that only a minority of women deliver on their exact EDD.
Encourage regular antenatal care.
π§ Quick Memory Tip
LMP β +7 days β β3 months β +1 year = EDD
40 weeks = 280 days from the first day of LMP.