Regular vacation refers to menstruation. If you have your period on the 1st, it may be the 9th to 19th that you are ovulating, or you may not be able to calculate it. If a woman’s menstruation is relatively regular, with a menstrual cycle of about 28 days, she will usually ovulate 14 days before her next period, and the 5 days before and the 4 days after ovulation, together with the day of ovulation, are known as the ovulation period for a total of 10 days, according to this method of calculating, it is probably the 9th to 19th is the ovulation period, and there is a possibility that you can get pregnant if you have intercourse during this period of time. If a woman’s menstruation is irregular, often early or late, can not calculate ovulation through menstruation, if you have a reproductive plan, you can use ovulation test paper to monitor ovulation, usually in the clean menstruation 4-5 days after the start to monitor, if there is a strong positive considered to be ovulation immediately. In addition, you can also go to the hospital to monitor the size of the follicle by ultrasound, usually when the follicle reaches 18~23mm, there will be ovulation. If you have any other questions, please consult your doctor.