A normal, full-term pregnancy is divided into 3 stages or trimesters. The first trimester is from 0-12 weeks of pregnancy. The second trimester is from 13-28 weeks. The third trimester is from 29-40 weeks. Each trimester is unique – your baby’s growth, your body’s changes, how you feel, testing that is offered – are all different among the first, second and third trimesters.