The third trimester of pregnancy typically lasts about 13 to 14 weeks.

Breakdown:

• Pregnancy is usually around 40 weeks in total.
• The third trimester starts at week 28 and continues until birth, which is usually around week 40.
• So, from week 28 to week 40 is approximately 13 weeks.

If you have any more questions about pregnancy stages or anything else, feel free to ask!