Clinically, there are two ways to calculate the time of pregnancy: the last menstrual period and ultrasound, but the time of pregnancy is not counted from the day of the formation of the fertilized egg. 1. Last menstrual period: For women who usually have regular menstrual cycles, it is recommended to start counting from the first day of the last menstrual period, i.e. the date of pregnancy. However, the calculation of the expected date of labor is as follows: the month is the month of the pregnant woman’s last menstrual period plus nine or minus three, while the date of the expected date of labor is the number of days of the pregnant woman’s last menstrual period plus seven. 2. Ultrasound projections: If a woman’s menstrual cycle is irregular, she can project the date of pregnancy by the length of the fetal buds. But also according to the fetal biparietal diameter, femur length, head and hip length and other general estimate of the age of the fetus, and then can also be projected to the expected date of delivery. If you want to be sure of the time of your pregnancy, it is recommended to go to the hospital for counseling.