It should be remembered that the duration of the menstrual cycle can vary and under normal condition of the body. Most often, the cycles of different duration can appear in young girls at puberty when the menstrual function only set. Can also change the cycle when moving from one geographical area to another, particularly when moving to a different time zone. But in this case the normal duration of the cycle is restored within two to three months.The cycle can change when taking hormonal contraceptive drugs. In this case, just the body gets the hormonal profile, due to the constant flow of contraceptives into the body, and menstrual bleeding occurs regularly, within 1-2 days after receiving another package which contains all the hormones in accordance with the phases of the normal cycle.In other cases, violations of menstrual cycle indicate the problems that arise in a woman's body. Often the duration of the cycle "gets off" with severe General diseases of the body, but is restored when adequate treatment and nutrition. The same goes for craze diets, especially in those cases when the body fails to receive the right amount of certain foods. This equally applies to fatty foods (cholesterol is the precursor to all hormones of the human body) and protein, which is necessarily necessary for tissue repair.To change the duration of the next cycle after abortion in any trimester, and this may occur after medical abortion for early pregnancy and after any intervention at a later. That is why doctors say that abortion, in addition to the risk of infection, affect the normal functioning of the endocrine glands – hypothalamus, engaged in the Central regulation of the cycle, and to the ovaries in which there is secretion of estrogen and progesterone and ova (eggs). Infrequent changes of the cycle after birth, and in this case approximately six months later, the cycle can be restored completely.Can also occur violation cycle in inflammatory and hormonal diseases of the body, and some vascular brain lesions, which affect a region of the hypothalamus.