Question 1

When does each trimester start and end?

Accepted Answer

The first trimester runs from week 1 through the end of week 12. The second trimester covers weeks 13 through 27. The third trimester begins at week 28 and continues until birth.

Question 2

Why do people define trimesters differently?

Accepted Answer

There is no single medical definition. Some clinicians use week 14 or week 27 as boundaries. SoftBump uses the common 13 / 28 boundaries.

Question 3

Can trimesters shift if my due date changes?

Accepted Answer

Yes. Trimesters are calculated backwards from your due date, so if a scan updates your due date the exact date ranges shift too.

Trimester Calculator

Frequently asked questions