Menstruation occurs once every two months, and if this is the pattern, 14 days before the next period is the day of ovulation, and the five days before and four days after the day of ovulation are the ovulation period. If menstruation is irregular, ultrasound or ovulation test paper is needed to monitor ovulation, so that the day of ovulation can also be derived and the ovulation period can be projected.
The normal menstrual cycle is about 28 days, and a delay of 7 days before or after is normal. However, if a woman has her period once every 2 months, her menstrual cycle is not between 21-35 days, but as long as her menstrual cycle is relatively constant, it is normal for her. So ovulation can be predicted based on menstruation.
However, if the menstrual cycle is not always two months, it means that the menstrual cycle is disordered, and the estimation of ovulation is inaccurate, which needs to be monitored with the help of ultrasound or ovulation test paper. It is advisable to consult a medical professional for details.