Understanding Pregnancy Calculation
How Pregnancy Dating Works
Pregnancy is calculated from the first day of your last menstrual period (LMP), not from conception. This is because most women don't know exactly when they ovulated, but usually remember their last period. A typical pregnancy lasts about 40 weeks (280 days) from the LMP. Your due date is an estimate - only about 5% of women deliver on their exact due date, with most delivering within 2 weeks before or after.
Trimesters Explained
- First Trimester: Weeks 1-12 (Early development)
- Second Trimester: Weeks 13-27 (Rapid growth)
- Third Trimester: Weeks 28-40 (Final preparation)
- Each trimester has unique symptoms and milestones
Pregnancy Terms to Know
- LMP: Last Menstrual Period
- EDD: Estimated Due Date
- Quickening: First fetal movements felt
- Viability: When baby could survive outside womb
- Full Term: 37-42 weeks gestation
Important Notes
- This calculator provides estimates only
- Your healthcare provider may adjust your due date after ultrasound
- Always consult your doctor about pregnancy concerns
- Every pregnancy is unique - milestones may vary