There are two ways to calculate the 40 days of pregnancy, the first is from the first day of the last menstrual period; the other is the calculation of the gestational age, which is from the day the fertilized egg is formed. The first day of the last menstrual period is the beginning of a cycle and can be used to calculate the week of pregnancy and the expected date of delivery. For those who have regular periods, the calculation of pregnancy from the first day of the last menstrual period is usually 2 weeks earlier than the time of ovulation and fertilization, and 3 weeks earlier than the time of fertilization of the egg, so that the whole cycle of pregnancy is calculated to be about 280 days, i.e. 40 weeks. The calculation of gestational age is related to ovulation, which cannot be determined. Usually, the 14th day before the next menstrual period is called the day of ovulation, and 4-5 days before and after the day of ovulation is the period of ovulation, during which ovulation is possible, and if you have sex during this period, it is difficult to determine the exact time of the beginning of pregnancy. In addition, since 40 days of pregnancy is the early pregnancy period, pregnant women need to quit smoking, alcohol, spicy and stimulating foods and pickled products, etc., and to ensure balanced nutrition and eat more green leafy vegetables to supplement vitamins and folic acid.