Naegele's Rule · Trimester Timeline · Weekly Milestones
| Trimester | Weeks | Key Developments |
|---|---|---|
| First | 1-12 | Organ formation, heartbeat at week 6, morning sickness peak |
| Second | 13-26 | Baby kicks, anatomy scan at 20 weeks, energy returns |
| Third | 27-40 | Rapid growth, lung maturity, nesting instinct, birth prep |
| When | What |
|---|---|
| Week 8-10 | First prenatal visit, dating ultrasound |
| Week 11-14 | First trimester screening (NT scan) |
| Week 18-22 | Anatomy scan (20-week ultrasound) |
| Week 24-28 | Glucose tolerance test |
| Week 36 | Group B strep test, weekly visits begin |
| Week 39-40 | Membrane sweep discussion, birth plan review |
⚕️ This calculator uses Naegele's Rule (LMP + 280 days, adjusted for cycle length). Actual due dates are estimates — only 5% of babies arrive on their due date. Consult your OB-GYN or midwife for personalized prenatal care.