A normal human pregnancy lasts 40 weeks and is divided into three distinct trimesters.
The first trimester lasts from week one to week 12. Though the body doesn’t change a lot on the outside during this trimester, hormonal changes begin occurring throughout the body as it prepares for the pregnancy. This causes a number of symptoms for most women, including fatigue, mood swings, nausea (morning sickness), tender and swollen breasts, headache and more.
During the second trimester, from week 13 to week 28, changes to the body become more visible. Physically, however, women often have an easier time during this trimester of the pregnancy. Many of the symptoms of the first trimester, such as morning sickness, will begin to subside. But a woman may experience new symptoms as the baby continues to grow, such as pain in the back, abdomen, thigh or groin, itchiness, swelling and stretch marks.
The third trimester lasts from week 29 to week 40, and it is the last trimester before the baby is born. A woman’s body may experience more symptoms as the baby continues to grow and put pressure on internal organs. Increased swelling, tender breasts, shortness of breath, heartburn and difficulty sleeping are just a few of the many common symptoms of this trimester.
A number of complications can occur during a pregnancy, either for the mother or the baby. Some of these are unavoidable, but women can minimize their risks by taking certain steps. Being under the care of a trusted prenatal care adviser is very important throughout pregnancy. Among other things, this health care professional can recommend needed tests and screenings.
Women can also help themselves by taking prenatal vitamins, eating a healthy diet and exercising in a safe and regular manner. Certain foods like raw fish, unpasteurized dairy products and certain meat products, as well as alcohol and tobacco, should be avoided during pregnancy.
SOURCES: U.S. Office on Women's Health