Healthline.com says, “Pregnancy date counting starts with the first day of your last normal menstruation cycle, and conception takes place in week 2. The first trimester lasts from the first through the 13th week of pregnancy. Although you may not look pregnant during the first trimester, your body is going through enormous changes as it accommodates a growing baby.”
They continue, “The second trimester (weeks 13-27) is the most comfortable period of time for the majority of pregnant women. Most of the early pregnancy symptoms will gradually disappear. You will likely feel a surge in energy levels during the daytime and be able to enjoy a more restful night’s sleep.”
The third trimester lasts from the 28th week through to the birth of your baby. During the third trimester, you’ll start seeing your healthcare provider more frequently.