The pregnancy cycle is the entire process between conception and delivery. A normal human pregnancy lasts approximately 40 weeks, or about 280 days, in 10 gestational months. There are two ways to calculate the pregnancy cycle, one is based on the date of the last menstrual period, and the other is based on the date of sexual intercourse or ovulation that caused the pregnancy. However, since the date that caused the pregnancy is often difficult to determine, the first day of the last menstrual period is often used in medicine as the start of the calculation of the expected date of delivery. If a woman’s menstruation takes 28 days as a menstrual cycle, 280 days of pregnancy is equivalent to 10 pregnancy months or 10 menstrual cycles, hence the term October pregnancy. A full-term delivery occurs between the 37th week of pregnancy and the 38th week of pregnancy, and a delivery within 42 weeks of pregnancy. Due to the length of the menstrual cycle and individual differences in the timing of ovulation, the expected date of delivery based on the last menstrual period may differ from the actual time of delivery by 1-2 weeks. If a woman is unsure of the time of her last menstrual period, she can go to the hospital for a checkup to determine the pregnancy cycle based on ultrasound detection of the fetus or measurement of the height of the uterine fundus, etc.