Pregnancy is the period in which the fetus or embryo develops in the womb, and a full term pregnancy usually lasts 38 weeks. The World Health Organization defines a full term pregnancy as lasting between 37 and 42 weeks. During the first 8 weeks of pregnancy, the developing offspring is called the embryo, and is then called a fetus from the end of that eight weeks until birth. Human pregnancy is divided into three trimester periods. The trimester periods make it easier to refer to the stages of the developing embryo or fetus. The first trimester is the riskiest in terms of the possibility of a miscarriage; during the second trimester the fetus can be better monitored by health professionals, and by the third trimester the ability of the fetus to survive outside the womb dramatically increases.
During pregnancy several changes occur in the woman's body, and some of those changes often correlate with which trimester the pregnancy is in. Understanding these changes and knowing what to expect can make pregnancy easier on many women. Pre-natal care is an important part of the development of the fetus, and increases the likelihood of having a healthy pregnancy that results in the birth of a healthy child. Pre-natal care includes taking pre-natal vitamins, which help ensure that both mother and baby have the nutrition they need. It also includes visits to a health care professional to monitor the progress of the pregnancy and the development of the unborn child.
Pregnancy changes the body of the woman, and almost always her lifestyle. Expectant mothers often have many questions about what they can and cannot do while pregnant, what they should and should not eat and drink, and what environmental factors may affect the development of the developing fetus. It often means changing diet and exercise routines, wardrobe, travel plans and work obligations. The best way to learn about all of these things is to talk with professionals, and luckily there are many books, magazines and other resources on the subject.