1. What is the Expected Date of Delivery?

The Expected Date of Delivery (EDD), also known as the due date, is calculated as 280 days (40 weeks) from the first day of the Last Menstrual Period (LMP). This is based on the typical duration of human pregnancy.

2. How Does the Calculator Work?

The calculator uses the Naegele's rule:

Where:

• \( \text{LMP} \) — First day of last menstrual period
• \( 280 \text{ days} \) — Equivalent to 40 weeks gestation

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

3. Importance of Due Date Calculation

Details: Accurate due date estimation is crucial for prenatal care scheduling, monitoring fetal growth, and determining the optimal time for delivery.

4. Using the Calculator

Tips: Enter the first day of your last menstrual period in the format YYYY-MM-DD. The calculator will add 280 days to determine your estimated due date.

5. Frequently Asked Questions (FAQ)

Q1: How accurate is this 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 estimation.

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

Q4: What's the difference between gestational age and fetal age?
A: Gestational age counts from LMP (about 2 weeks older than fetal age which counts from conception).

Q5: How is the due date adjusted for IVF pregnancies?
A: For IVF, the due date is calculated based on the embryo transfer date plus 266 days (or 263 days for day 3 embryos).