Nidation is the process of egg fixation formed after the union of the female ovule with the male sperm that occurs in the womb of the woman.
Menstruation it's the monthly bleeding which occurs as a result of desquamation of the inner layer of the uterus, the endometrium.
The woman after puberty presents hormonal changes and initiates the menstrual cycles that will occur until the onset of menopause. With each menstrual cycle, the inner layer of the uterus thickens to receive the fertilized egg. When it reaches the apex of its thickness, and there being no fertilization, the endometrium is peeling off, and therefore there is bleeding which is menstruation. If the egg is fertilized, the egg will be implanted in the endometrium and begin to develop until the embryo stage and then the fetus. This fixing process is called nidation.
Therefore, nidation and menstruation are independent processes but occur in the womb of the woman.
