1. What is OB Wheel EDD Calculation?

The OB Wheel EDD (Estimated Due Date) calculation is a standard method used in obstetrics to determine the expected delivery date based on the last menstrual period (LMP). It follows Naegele's rule, adding 280 days (40 weeks) to the first day of the LMP.

2. How Does the Calculator Work?

The calculator uses the standard OB Wheel formula:

Where:

• \( EDD \) — Estimated Due Date
• \( LMP \) — Last Menstrual Period (first day)
• \( 280 \text{ days} \) — Standard gestation period (40 weeks)

Explanation: This calculation assumes a regular 28-day menstrual cycle and ovulation occurring on day 14. The calculator also provides current gestation in weeks and days.

3. Importance of EDD Calculation

Details: Accurate EDD calculation is crucial for prenatal care scheduling, fetal growth monitoring, timing of prenatal tests, and planning for delivery. It helps healthcare providers track pregnancy progression and identify potential complications.

4. Using the Calculator

Tips: Enter the first day of your last menstrual period in the date field. Ensure the date is accurate for the most reliable EDD calculation. The calculator will also show your current gestation period.

5. Frequently Asked Questions (FAQ)

Q1: How accurate is the OB Wheel calculation?
A: The OB Wheel method is about 70-80% accurate for women with regular 28-day cycles. Ultrasound dating in the first trimester is more precise.

Q2: What if my cycle is longer or shorter than 28 days?
A: For irregular cycles, the calculation may need adjustment. Typically, add or subtract days based on your cycle length difference from 28 days.

Q3: When should I confirm my due date with ultrasound?
A: Early ultrasound (8-12 weeks) provides the most accurate dating. Later ultrasounds are less reliable for dating purposes.

Q4: What percentage of babies are born on their due date?
A: Only about 4-5% of babies are born exactly on their due date. Most births occur within two weeks before or after the EDD.

Q5: Can the due date change during pregnancy?
A: Yes, healthcare providers may adjust the due date based on early ultrasound measurements or if fetal growth doesn't match the LMP-based calculation.