Naegele's Rule formula:

\[\text{EDD} = \text{LMP} - 3\,\text{months} + 7\,\text{days} + 1\,\text{year}\]

Or equivalently: Add 9 months and 7 days to LMP

Calculation:

• LMP: 10th September
• Subtract 3 months: 10th June
• Add 7 days: 17th June
• Add 1 year (next year)

Therefore, EDD = 17th June (next year)

Normal pregnancy duration: \(280\,\text{days}\) or \(40\,\text{weeks}\) from LMP \(= 266\,\text{days}\) from conception.

Important caveat: Naegele's rule assumes a regular 28-day cycle with ovulation on Day 14. Adjust for irregular cycles accordingly. Ultrasound (especially first trimester CRL) is more accurate for dating.