Weeks can be approximated by the length of the buds (cm) + 6.5 as indicated by the ultrasound, which should be taken into account under the supervision of a doctor. For those who cannot remember their last menstrual period or those who conceived without menstruation during breastfeeding or those who have long menstrual cycles, the number of weeks of pregnancy can be estimated by ultrasound examination during early pregnancy, which is applicable to those who have been pregnant for 12 weeks or more. When the ultrasound indicates the length of the fetal buds (cm), the week of pregnancy can be calculated by adding 6.5 to the length of the fetal buds. Those who do not have early ultrasound examination can also check the week of pregnancy according to the time of early pregnancy reaction and the time of fetal movement, etc., which need to be checked by a professional physician, and also combined with the actual situation of the pregnant woman. During pregnancy, it is important to follow the doctor’s instructions to take obstetric checkups on time and review the ultrasound examination regularly to find out whether the growth and development of the fetus is in line with the week of pregnancy.