How Due Date is Calculated
The standard method for calculating estimated due date (EDD) is Naegele's Rule, developed by German obstetrician Franz Naegele in 1812. It adds 280 days (40 weeks) to the first day of your last menstrual period (LMP). This assumes a regular 28-day cycle with ovulation on day 14.
Example: LMP = 1 January 2025
EDD = 8 October 2025
Pregnancy Trimesters
| Trimester | Weeks | Key Milestones |
|---|---|---|
| First | 1–12 weeks | Organ formation, morning sickness, first heartbeat |
| Second | 13–26 weeks | Baby moves, anatomy scan, gender reveal |
| Third | 27–40 weeks | Rapid growth, birth preparation, maternity leave |
⚠️ This calculator provides an estimate only. Actual due date may differ based on cycle length, conception date and ultrasound dating. Always consult your obstetrician for accurate pregnancy dating.
Important Pregnancy Dates
- 8 weeks: First antenatal visit recommended
- 11–13 weeks: First trimester screening (NT scan + blood test)
- 18–20 weeks: Anomaly (anatomy) scan
- 24–28 weeks: Gestational diabetes screening
- 36 weeks: Weekly check-ups begin
- 40 weeks: Estimated due date
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