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The stages of pregnancy are a series of distinct developmental milestones used to divide a pregnancy into segments. Dividing pregnancies into stages is important for assessing pregnancy health in addition to helping people know what to expect during various pregnancy stages. It can also be important from a legal perspective in many areas of the world where abortion procedures are limited by law, depending on the stage of pregnancy a woman has reached. There are several different ways to look at the stages of pregnancy.
One common system used to break up pregnancies is the trimester system. A pregnancy lasts approximately 40 weeks and can be broken into a first, second, and third trimester. The first trimester lasts from weeks one to 12, the second from weeks 13 to 28, and the third from weeks 29-50. At each of these stages of pregnancy, the fetus develops new characteristics and the mother experiences a variety of symptoms associated with the development of the pregnancy.
People can also divide pregnancies into months. Women can expect different symptoms from month to month, ranging from the nausea and vomiting common in earlier months to discomfort and pain in the later months of pregnancy as the fetus gains weight and settles in the uterus. Monthly milestones are important for assessing fetal development during prenatal exams, as doctors know what to expect at different months and can take note if something appears abnormally.
The individual weeks of a pregnancy are also treated as stages of pregnancy. Each week will be marked by a variety of developmental milestones from the emergence of internal organs to the development of fingernails. The weeks are used by physicians to develop prenatal appointment schedules. It is also important to be aware of which week a woman's pregnancy is in when recommending diagnostic testing and prenatal screening, as many such tests are only effective at very specific stages of pregnancy.
Books and leaflets providing pregnant women with information about what to expect throughout a pregnancy are commonly divided into different stages of pregnancy to provide a quick reference for patients. These books provide information about the level of fetal development at each stage in addition to the symptoms associated with different phases of a pregnancy. Being prepared with information can help women manage a pregnancy more safely and effectively, in addition to addressing concerns women may have as their bodies adjust to the pregnancy.