The idea of trimesters are just a way that we talk about the various things going on in a woman’s body at different points during her pregnancy. Literally, a “trimester” is a one third section of a pregnancy. There are, then, three trimesters to a pregnancy, each lasting roughly 13 or 14 weeks.
Trimesters are a way to talk in shorthand about what’s going on. We talk about different pregnancy symptoms, how your baby is growing and developing, your nutritional needs and even psychological changes happening during each trimester.
During the first trimester, for example, your baby is growing from an embryo into a fetus. The first trimester starts the day of conception, although the weeks of pregnancy are actually measured not from conception but from the start of a woman’s last period. A good portion of the first trimester, a woman may not know she’s pregnant. This is, however, when certain symptoms of pregnancy, such as morning sickness, tend to be at their worst. This is also a common time for women to feel some degree or another of fatigue.
The second trimester of pregnancy is the time when a woman tends to feel her best. She’s usually past the morning sickness stage, and her baby hasn’t yet grown so large as to become uncomfortable or a nuisance. This is also the time when a woman is likely to feel her baby start to move.
The final trimester is the third trimester. This is when your baby will grow the most. This trimester tends to have a lot of back ache, and problems with bladder control. The third trimester ends when your baby is born.
Finally, it’s worth remembering that every woman, and every pregnancy, is different. The trimesters are an imaginary construct, and it’s not unheard of for a woman to have “first trimester” symptoms all through pregnancy, or for her back to start aching in the second trimester instead of the third.