The first day of menstrual bleeding is counted as DAY ONE of the menstrual cycle. Menstrual bleeding usually lasts 3-5 days. By day 7, pituitary hormones begin to trigger the development of an egg in the ovary. As an egg ripens, it is secreting estrogen, which begins to stimulate the development of the lining inside the uterus. For most women, ovulation does not cause any symptoms.
Ovulation completes the first phase of the cycle.
The egg travels through the fallopian tube toward the uterus. Simultaneously, during ovulation, the estrogen level drops and progesterone levels begin to rise. This causes additional changes in the uterine lining, preparing it for implantation should fertilization occur. If sperm fertilizes the egg, it will implant in the thick, spongy lining that has been developing in the uterus. This establishes a pregnancy.