If you have a 30-day menstrual cycle on the 3rd, and the day of ovulation is the 19th, the 4 days before and the 5 days after the day of ovulation plus the day of ovulation, a total of 10 days belong to the danger period. According to the calculation of the menstrual cycle, in the ovulation period coitus is more likely to be pregnant, the menstrual irregularity of women ovulation is not good to estimate, can not be accurately calculated by the menstrual cycle of ovulation, it is best to through the ovulation paper or ultrasound, you can determine whether there is a normal ovulation. Do not intend to get pregnant is not recommended in the ovulation period, if you need to take reasonable contraceptive methods, if you intend to get pregnant is best in the ovulation day before and after the 1-2 days of coitus, the chances of getting pregnant are greater. When endocrine disorders occur, the time of ovulation is not easy to calculate, through ultrasound to check the size of the follicle, if necessary, you can use reasonable ovulation drugs.