Pregnancy Due Date Calculator: Week-by-Week Timeline
How Your Due Date Is Calculated
The standard method (Naegele’s rule) adds 280 days (40 weeks) to the first day of your last menstrual period (LMP). This assumes a 28-day cycle with ovulation on day 14. If your cycle is longer or shorter, your actual due date may differ by a few days. Only 5% of babies arrive exactly on their due date — consider it an estimate, not an appointment.
Trimester Timeline
| Trimester | Weeks | Key Developments |
|---|---|---|
| First | 1–12 | Organ formation, heartbeat detectable by week 6–7, morning sickness peaks |
| Second | 13–26 | Baby movements felt, anatomy scan (18–20 weeks), energy returns |
| Third | 27–40 | Rapid growth, baby positions head-down, preparation for delivery |
Essential Prenatal Checkup Schedule
- Week 6–8: First ultrasound (confirm viability, heartbeat)
- Week 11–13: NT scan (nuchal translucency for chromosomal screening)
- Week 18–20: Anomaly scan (detailed anatomy check)
- Week 24–28: Glucose tolerance test (gestational diabetes screening)
- Week 32–36: Growth scan, birth plan discussion
- Week 36+: Weekly visits, cervical checks
Use the pregnancy calculator to find your due date, current week, and trimester based on your LMP or conception date.