1. What is Reverse EDD Calculation?

Reverse EDD calculation determines the Last Menstrual Period (LMP) from a known Estimated Due Date (EDD). This is useful when the due date is known but the start date of the last menstrual period needs to be calculated.

2. How Does the Calculator Work?

The calculator uses the reverse Naegele's rule:

Where:

• \( LMP \) — Last Menstrual Period (start date)
• \( EDD \) — Estimated Due Date
• \( 280 \text{ days} \) — Standard pregnancy duration (40 weeks)

Explanation: This calculation reverses the standard due date calculation by subtracting the typical 280-day pregnancy duration from the known due date.

3. Importance of LMP Calculation

Details: Knowing the LMP is crucial for accurate pregnancy dating, determining gestational age, scheduling prenatal tests, and monitoring fetal development milestones.

4. Using the Calculator

Tips: Enter the estimated due date in the date field. The calculator will automatically compute the corresponding last menstrual period date.

5. Frequently Asked Questions (FAQ)

Q1: Why 280 days for pregnancy calculation?
A: 280 days represents 40 weeks of gestation, which is the standard duration used in obstetric calculations from LMP.

Q2: Is this calculation always accurate?
A: While 280 days is the standard, actual pregnancy duration can vary. This provides an estimate based on conventional obstetric dating.

Q3: What if I know the conception date instead of EDD?
A: If conception date is known, LMP is typically estimated as 14 days before conception date for regular 28-day cycles.

Q4: How does this help in clinical practice?
A: It helps healthcare providers determine when prenatal care should have begun and assess pregnancy progression timing.

Q5: Are there variations in pregnancy duration?
A: Yes, normal pregnancy can range from 37-42 weeks. This calculation uses the standard 40-week reference point.