1. What is the Pregnancy Due Date Calculation?

The pregnancy due date is calculated by adding 280 days (40 weeks) to the first day of the last menstrual period (LMP). This is known as Naegele's rule and is the standard method for estimating due dates.

2. How Does the Calculator Work?

The calculator uses the simple formula:

Where:

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

Explanation: This calculation assumes a regular 28-day menstrual cycle with ovulation occurring on day 14. The actual conception date is typically about two weeks after the LMP.

3. Importance of Due Date Calculation

Details: An accurate due date helps monitor fetal development, schedule important prenatal tests, and determine if the pregnancy is progressing normally. It's also crucial for planning maternity leave and preparing for delivery.

4. Using the Calculator

Tips: Enter the first day of your last menstrual period in the format YYYY-MM-DD. Make sure to use the first day of bleeding, not the last day.

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 the estimated date.

Q2: What if my cycles aren't 28 days long?
A: The calculation may need adjustment. Consult your healthcare provider who can adjust based on your cycle length.

Q3: When will my healthcare provider confirm the due date?
A: Typically during the first ultrasound (dating scan) between 8-14 weeks, which provides a more accurate estimate.

Q4: Can the due date change?
A: Yes, especially if early ultrasound measurements differ significantly from the LMP-based calculation.

Q5: What's considered full term?
A: Between 37 weeks (259 days) and 42 weeks (294 days) from LMP.