1. What is Pregnancy Due Date Calculation?

The pregnancy due date, also known as the estimated date of delivery (EDD), is calculated as 280 days (40 weeks) from the first day of the last menstrual period (LMP). This is based on Naegele's rule, the standard method for estimating due dates.

2. How Does the Calculator Work?

The calculator uses the standard formula:

Where:

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

Explanation: The calculation assumes a regular 28-day menstrual cycle with ovulation occurring on day 14. The 280 days accounts for 266 days of pregnancy plus 14 days from LMP to conception.

3. Importance of Due Date Calculation

Details: Accurate due date estimation is crucial for proper prenatal care, monitoring fetal development, scheduling important tests, and determining if pregnancy goes post-term.

4. Using the Calculator

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

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 more accurate dating than LMP-based calculation.

Q3: Does this work for IVF pregnancies?
A: For IVF, use the embryo transfer date plus 266 days (or 263 days for day-5 embryos).

Q4: Why 280 days if pregnancy is 9 months?
A: Pregnancy is actually about 9.5 lunar months (4 weeks each). Calendar months vary in length.

Q5: When should I contact my doctor about a late baby?
A: Most providers recommend monitoring after 41 weeks and induction by 42 weeks to reduce risks.