1. What is OB Wheel Pregnancy Calculator?

The OB Wheel Pregnancy Calculator estimates the due date based on the last menstrual period (LMP) using the standard obstetric calculation of LMP + 280 days. This method is commonly used in clinical practice for pregnancy dating.

2. How Does the Calculator Work?

The calculator uses the standard obstetric formula:

Where:

• \( LMP \) — First day of last menstrual period
• \( 280 days \) — Standard duration of pregnancy (40 weeks)

Explanation: This calculation assumes a regular 28-day menstrual cycle and ovulation occurring on day 14. The due date represents the estimated date of delivery (EDD).

3. Importance of Due Date Calculation

Details: Accurate due date estimation is crucial for monitoring fetal development, scheduling prenatal tests, determining gestational age, and planning for delivery.

4. Using the Calculator

Tips: Enter the first day of your last menstrual period in the date field. The calculator will provide the estimated due date and current gestational age.

5. Frequently Asked Questions (FAQ)

Q1: How accurate is the LMP method?
A: The LMP method is reasonably accurate for women with regular cycles. First-trimester ultrasound dating is more precise and is the gold standard.

Q2: What if my cycles are irregular?
A: For irregular cycles, the LMP method may be less accurate. An early ultrasound provides more reliable dating.

Q3: Why 280 days instead of 9 months?
A: Pregnancy is calculated as 40 weeks from LMP, which equals 280 days. This accounts for the fact that conception typically occurs about 2 weeks after LMP.

Q4: Can the due date change?
A: Yes, healthcare providers may adjust the due date based on ultrasound measurements, especially if there's a significant difference from LMP dating.

Q5: What percentage of babies are born on their due date?
A: Only about 5% of babies are born exactly on their due date. Most births occur within 2 weeks before or after the estimated due date.