The first calculation method: one month is four weeks of pregnancy, counting from the last menstrual period. The early stage of pregnancy is within the third trimester, i.e. within 12 weeks of pregnancy; the middle stage of pregnancy is within 13 weeks to 28 weeks of pregnancy; the late stage of pregnancy is within 28 weeks to 40 weeks of pregnancy. The second calculation method: early pregnancy is the first, second and third trimesters; middle pregnancy is the fourth, fifth and sixth trimesters; and late pregnancy is the seventh, eighth and ninth trimesters. During pregnancy, prenatal checkups should be done, with the focus on Down’s syndrome screening and NT test in early pregnancy; non-invasive DNA and ultrasound screening in mid-pregnancy; and monitoring the fetal development and the condition of amniotic fluid and placenta in late pregnancy, especially whether the fetal heartbeat is within the normal range and whether the fetus is moving well, as well as actively doing the work to prevent pregnancy complications. During the whole pregnancy, it is necessary to pay attention to proper rest, to eat a reasonable and nutritious diet, and to monitor the growth and development of the fetus dynamically.