Pregnancy is carried out in the adult woman after fertilization of the egg by a sperm. This process can be completed between the twelfth and fifteenth day of menstruation. This day when the egg meets the sperm is the first day of the day Pregnancy. On the second day, this egg descends to the uterus, which has formed itself and made a thick blanket to receive the fertilized egg, where it excretes in the lining of the uterus to be the fetus; pregnancy starts from the woman, and begins counting days and months to receive it.
Usually the pregnancy period is nine months and ten days, increasing or decreasing depending on the condition of the woman and according to the general situation of pregnancy, but this period on average is the pregnancy period for most women. The days of pregnancy are calculated from the day of egg fertilization. When a woman knows that she is pregnant, she is counted 12 days after the first day of menstrual bleeding; this day is considered the first day of her pregnancy. For example, if the first day of menstrual bleeding is the first of the month; the twelfth day is the first day of fertilization, and the age of the semen is one day on the thirteenth day. Thus, the twelfth day of each month is the date of entering the next month , But care must be taken to transfer the days between the months, in the sense that the woman will be aware of the months that have a number of thirty-one days (31) days, this will make the month of pregnancy less days of the following month, for example, if the month was entered in the twelfth as in the previous example, In August, a 31-day month, she enters her next month of pregnancy on the eleventh day of the month September.
Some doctors tend to calculate the months of pregnancy differently from the ones we mentioned earlier, since gestational age is usually forty (40) weeks, equivalent to nine months and ten days; they have adopted the principle that every four weeks is equivalent to a month, 10 months, but here the doctor considers that the date changes from month to month. The calculation of the month by four weeks means that the month of pregnancy is twenty-eight (28) days, not 30 days. The first day of pregnancy is adopted as the first day of pregnancy, as mentioned in the previous example, since the date of pregnancy is not different according to the method of calculating the months of pregnancy between doctors in different ways of calculating the months of pregnancy.