How your pregnancy timeline is built
Enter the first day of your last period, your due date or your conception date. The calculator anchors week 0 on the first day of your last period and lays out every week up to 42 weeks, each with its exact start and end dates, a one-line note about what typically happens, and a link to the full week page. Your current week is highlighted, and above the calendar you will see your progress through the trimesters and cards for the previous, current and next week.
The three trimesters
| Trimester | Weeks | Months (approx.) | Typical focus |
|---|---|---|---|
| First | Week 1 to 13 + 6 days | Months 1–3 | Confirming the pregnancy, dating, early screening |
| Second | Week 14 to 27 + 6 days | Months 4–6 | Anatomy scan, first movements, glucose screening |
| Third | Week 28 to birth (40 weeks ≈ due date) | Months 7–9 | Growth, position, birth preparation |
First trimester: weeks 1–13
The first trimester starts before conception, on the first day of the last period. Conception usually happens around week 2, implantation in weeks 3–4, and a home test often turns positive around week 4. The major organs begin forming during weeks 5–10, after which the developing baby is called a fetus. This trimester commonly includes the first prenatal visit and a dating scan.
Second trimester: weeks 14–27
Often the most comfortable stretch. Nausea usually eases, the bump becomes visible and first movements are typically felt between about 16 and 22 weeks. The detailed anatomy scan is commonly offered between 18 and 22 weeks, and glucose screening between 24 and 28 weeks.
Third trimester: weeks 28–40+
The focus moves to growth and preparation for birth. Appointments usually become more frequent, many babies turn head-down, and the pregnancy becomes early term at 37 weeks, full term at 39 weeks and reaches the estimated due date at 40 weeks.
Key milestones on the timeline
| Weeks | Milestone |
|---|---|
| ≈ 2 | Ovulation and conception (28-day cycle) |
| ≈ 4 | Missed period; home test often positive |
| ≈ 6 | Cardiac activity often visible on an early scan |
| 11–13+6 | First-trimester screening window |
| 14 | Second trimester begins |
| 18–22 | Common anatomy-scan window |
| 20 | Halfway point |
| 28 | Third trimester begins |
| 37 / 39 / 40 | Early term / full term / estimated due date |
Exact schedules differ between countries and providers, so treat these as typical timings rather than a plan for your care.
Using the timeline alongside your care
Many people print the timeline and keep it with their pregnancy notes, or share the link with a partner. If your due date changes after a scan, recalculate in “Due date” mode so the timeline matches your provider’s dating. For month-based planning, the Pregnancy Month Calculator groups the same weeks into months, and the Days Until Due Date Calculator counts down to the big day.