1. What is the Due Date Calculation?

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

2. How Does the Calculator Work?

The calculator uses the standard formula:

Where:

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

Explanation: This calculation assumes a regular 28-day menstrual cycle with ovulation occurring on day 14. The actual delivery date may vary by ±2 weeks.

3. Importance of Due Date Estimation

Details: An accurate due date helps monitor fetal development, schedule prenatal tests at appropriate times, and identify potential preterm or post-term pregnancies.

4. Using the Calculator

Tips: Enter the first day of your last menstrual period in the format YYYY-MM-DD. The calculator will add 280 days to this date to estimate your due date.

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.

Q2: What if my cycles aren't 28 days?
A: For irregular cycles, your healthcare provider may adjust the due date based on early ultrasound measurements.

Q3: Can the due date change?
A: Yes, early ultrasound (especially first trimester) may lead to adjustment of the due date if it differs significantly from LMP-based calculation.

Q4: What's the difference between gestational age and fetal age?
A: Gestational age counts from LMP (about 2 weeks older than fetal age which counts from conception).

Q5: How is due date calculated for IVF pregnancies?
A: For IVF, the due date is typically calculated from the embryo transfer date plus 266 days (or 263 days for day 5 embryos).