1. What is the Pregnancy Wheel Calculator?

The Pregnancy Wheel Calculator determines the Last Menstrual Period (LMP) from the Estimated Due Date (EDD) using the standard obstetric calculation of 280 days (40 weeks) gestation.

2. How Does the Calculator Work?

The calculator uses the pregnancy wheel formula:

Where:

• \( LMP \) — Last Menstrual Period (date)
• \( EDD \) — Estimated Due Date (date)
• \( 280 \) — Standard gestation period in days

Explanation: This calculation is based on Naegele's rule, which assumes a 28-day menstrual cycle and ovulation occurring on day 14.

3. Importance of LMP Calculation

Details: Accurate LMP determination is crucial for establishing gestational age, scheduling prenatal screenings, monitoring fetal development, and planning for delivery.

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 is 280 days used for pregnancy calculation?
A: 280 days represents 40 weeks of gestation, which is the standard duration used in obstetric practice based on average pregnancy length.

Q2: What if my menstrual cycle isn't 28 days?
A: This calculation assumes a 28-day cycle. For irregular cycles, ultrasound dating in early pregnancy is more accurate for determining gestational age.

Q3: How accurate is this calculation?
A: It provides a good estimate, but first-trimester ultrasound is considered the most accurate method for dating a pregnancy.

Q4: Can this be used for IVF pregnancies?
A: For IVF pregnancies, the embryo transfer date is used instead of LMP for more precise dating.

Q5: What is Naegele's rule?
A: Naegele's rule is the standard method for calculating EDD: add 7 days to LMP, then subtract 3 months (or add 9 months).