Unlike men, who are fertile all the time, there is only a small window each month when a woman is fertile and can get pregnant. When it comes to identifying that time, there are four main signs in a woman's body

• Mucus: Throughout her menstrual cycle, a woman will produce various discharges, which she can use to evaluate her fertility. The most important of these discharges, commonly known as mucus, is produced by glands in the cervix. A woman can observe changes in the mucus sensation and appearance to gain insight into her fertility status. 
• Temperature: Following ovulation, a woman’s basal body temperature increases by about 0.4 °F.
• Cervix: Around the time of ovulation (i.e., when a woman is fertile), the cervix position is high and feels soft and open. After ovulation, the cervix position lowers and feels firm and closed.
• Hormones: In the days leading up to ovulation, a woman's estrogen hormone level rises and then spikes. Around the same time, there is a spike in another hormone—luteinizing hormone. Both of these hormones can be detected in a woman's urine.