The number of the 12th menstruation ovulation is the number of women need to be combined with the female menstrual cycle to analyze.
For the regular menstrual cycle in 28-30 days for women, the day of ovulation in the next menstrual period 14 days before the 12th day of ovulation is about the 27th, 5 days before ovulation and 4 days after ovulation belong to the ovulation period, ovulation in the 22nd-next month around the 1st, this period of sex is the most likely to get pregnant, such as fertilization plan to reasonable arrangements for sex, such as don’t want to get pregnant should be a good contraceptive measures.
But if the menstrual cycle is not regular, the time of ovulation is not fixed, not good to calculate the ovulation period, you can use ovulation test paper to monitor the ovulation situation in about one week after the menstrual period is clean, or recommended to go to the hospital to do ultrasound to monitor follicular development, can be speculated that the approximate time of ovulation.