1. What is the Estimated Due Date?

The estimated due date (EDD) is the approximate date when a pregnant woman is expected to deliver. It's calculated as 280 days (40 weeks) from the first day of the last menstrual period (LMP). This is known as Naegele's rule.

2. How Does the Calculator Work?

The calculator uses the standard obstetric formula:

Where:

• LMP — First day of last menstrual period
• 280 days — Equivalent to 40 weeks gestation

Note: This calculation assumes a regular 28-day menstrual cycle with ovulation occurring on day 14.

3. Importance of Due Date Calculation

Clinical Significance: The estimated due date helps healthcare providers monitor fetal growth, schedule prenatal tests at appropriate times, and determine if a pregnancy is progressing normally or if intervention might be needed.

4. Using the Calculator

Instructions: Enter the first day of your last menstrual period in the format YYYY-MM-DD. The calculator will display your estimated due date and current gestational age.

5. Frequently Asked Questions (FAQ)

Q1: How accurate is this due date calculation?
A: Only about 5% of women deliver on their exact due date. Most deliver within 2 weeks before or after.

Q2: What if my cycles aren't regular?
A: For irregular cycles, an early ultrasound provides a more accurate due date estimate.

Q3: Why 280 days if pregnancy is 9 months?
A: Pregnancy is actually about 9.5 months (40 weeks) when counted from LMP, since conception typically occurs about 2 weeks after LMP.

Q4: What if I know my conception date?
A: If you know conception date, you can calculate due date by adding 266 days (38 weeks).

Q5: When should I see my doctor after calculating my due date?
A: Schedule your first prenatal visit within the first 8 weeks of pregnancy for optimal care.