If the menstrual cycle is regular for 28 days and the period is 5 days, the pregnancy is usually easy to get pregnant about 9 days after the menstrual period is clean; if the menstrual period is irregular, the pregnancy is easy to get pregnant about 14 days before the next menstrual period, and it is impossible to project how many days after the menstrual period is clean the pregnancy is easy to get pregnant. The fertile period for women is 4~5 days before and after ovulation, which usually occurs about 14 days before the next menstrual period. If menstruation is regular, this can be extrapolated. For example, if the menstrual cycle lasts 28 days and the menstrual period lasts 5 days, the fertile period will be around 9 days after the menstrual period has been cleared. If menstruation is irregular, about 14 days before the next menstrual period, it is not possible to project how many days after the menstrual period is clean for easy pregnancy. Estimates of susceptibility to pregnancy based on the menstrual cycle are inaccurate and not very reliable. Fertility can be guided by biphasic thermometry, cervical mucus observation and ultrasound monitoring. It is advisable to seek medical advice and consultation if needed and if there is any discomfort.