A trimester is simply a way to divide something, in this case pregnancy, into three roughly equal sections. While talking about pregnancy in terms of trimesters can be an effective way to describe what is occurring during pregnancy, the fact of the matter is that these divisions are completely arbitrary, and your body has no special way to know that, when you go to bed one night you are in the first trimester, and when you wake up in the morning you are in the second trimester.
The first trimester of pregnancy tends to include, roughly, the first three months or the first 14 weeks or so of your pregnancy. During your first trimester of pregnancy, you will experience many pregnancy symptoms. While these symptoms will vary from one woman to the next, and even from one pregnancy to the next, it is likely that you will have at least some of them. These can include breast tenderness or swelling, nausea (called “morning sickness”), tiredness, and frequent urination. During the first trimester, you should focus on prenatal care, including diet and exercise, as well as regular prenatal doctor visits.
The second trimester of pregnancy encompasses the middle portion of pregnancy, from month three through month six, or roughly another 14 weeks. The second trimester tends to be the best for many pregnant women, in terms of how they feel. This is also the time that you will start to feel your baby moving.
The third trimester of pregnancy lasts from the beginning of month seven through the end of your pregnancy, or somewhere around another 14 weeks. During the third trimester, your baby will grow the most and your belly will get bigger. You will probably take childbirth or breastfeeding classes. These last days of pregnancy are often the most uncomfortable, and often the most anxious for expectant parents.
Throughout pregnancy, it is important that you take care of yourself and your baby, regardless of which trimester exactly you are in. Good nutrition, exercise, prenatal medical care, and just generally being informed about the issues surrounding pregnancy and childbirth will help your pregnancy to be a successful one.