To determine the period in which the pregnancy is most likely need to have a calendar of menstruation. Experts to obtain accurate results it is recommended to use the data for eight or even twelve calendar months. It should highlight the shortest and longest menstrual cycle and then take away from each digit 10 and 18. For example, a short menstrual cycle in women was 25 days and the longest 29. In this case, the calculation would look like:
25-10 and 29-18 = 15 = 9
Numeral 15 indicates the number of days for adverse pregnancy early in the cycle, figure 9 - end. For example, a girl's menstruation ends 1st day of the month, so "safe" days for it to be 1-15 numbers. If the onset of menstruation occur in 27 of the month, the "safe" period at the end of the cycle will be from 22 to 27. The danger for this girl is the period from the 15th of 22.
In the "dangerous" days, women either do refuse sex or use contraception. It should be noted that the method of contraception on the calendar is very inaccurate. If suddenly a woman hit by a cycle, then the "dangerous" days will be different. When an active sex life, as well as in other cases can be produced not one, but two eggs, which also leads to unwanted pregnancy.
Gynecologists recommend that women use more reliable contraceptives than the calendar method. Its effectiveness may be affected: changes in lifestyle, sexual partner, the intensity of sexual activity, a change in hormonal levels, stress, exercise, and a number of other factors. Most often aborted women using this method of contraception.