The nine-month pregnancy term is divided into three trimesters, each about 13 weeks in duration.
The first trimester of pregnancy begins with the first day of a woman's last period before realizing she was pregnant. This means that a woman is technically four weeks into her first trimester by the time she can take a home test for pregnancy with accurate results. Often, women notice physical and emotional changes in their body before a test can detect pregnancy. The first trimester is riddled with the typical pregnancy symptoms, such as morning sickness, food cravings and aversions, tender breasts, emotional mood swings, and an increased need to urinate, among other symptoms. The baby will begin to develop from an embryo during this trimester.
In week 13, the second trimester begins. This brings with it the end to the unpleasant symptoms of the first trimester and the beginning of weight gain and further fetal development. By week 14, it will be possible for a woman's health care provider to determine the baby's gender. The baby develops bones and begins to hear and will begin to respond to people's voices by week 25.
Week 28 marks the beginning of the third trimester. During this time, the baby will gain weight rapidly and prepare for delivery by forming a waxy coating around itself, opening its eyes, practices breathing and detects light. The baby will also turn upside to prepare for delivery. This is typically an uncomfortable time for the woman as the child will be pressing on her bladder and internal organs, but by week 40 or 42 into a woman's pregnancy, the third trimester will be complete!