If an ovum is fetilised by a sperm, a zygote will form and develop into an embryo which will implant itself to the uterus wall. The woman is then said to be pregnant and her menstrual cycle will stop until the baby is born.
If the ovum is not fertilised, it will die after 24-36 hours. The tissue layer on the thick and soft uterus wall will break off and be expelled together with blood through the vagina are menstrual discharge.
The fertile phase is the period when ovulation is most likely to happen.