Calculating Your Due Date
The estimated due date (EDD) is calculated by adding 280 days (40 weeks) to the first day of your last menstrual period (LMP). This is based on Naegele's rule and assumes a 28-day cycle with ovulation on day 14. Only about 5% of babies arrive exactly on their due date.
Pregnancy Trimesters
First Trimester: Weeks 1-12 (organ formation, morning sickness common)
Second Trimester: Weeks 13-26 (energy returns, baby movement felt)
Third Trimester: Weeks 27-40 (rapid growth, preparation for birth)
Full term is 37-42 weeks.
Accuracy of Due Dates
LMP-based calculations assume regular 28-day cycles. Early ultrasound (6-12 weeks) is more accurate, especially if cycles are irregular. Most babies are born between 37-41 weeks. Only 4% are born on the exact due date.
Quick Tips
- BMI alone doesn't reflect overall health
- TDEE varies based on activity level
- Consult a healthcare professional for medical decisions
Frequently Asked Questions
It's an estimate. Only 5% deliver exactly on due date. Most deliver within 2 weeks before or after.
Due dates based on LMP are less accurate. Early ultrasound provides better estimate.
37-42 weeks. Babies born 37-39 weeks are early term, 39-41 weeks is full term.
Doctors may adjust based on early ultrasound measurements if significantly different from LMP date.
Most doctors induce labor by 41-42 weeks to reduce risks.