How does period delay a month to be pregnant to return a responsibility

Menstruation delayed a month, but not pregnant, the main possible reasons include: 1, because of thyroid dysfunction, affecting the secretion of the gonad axis, resulting in menstruation is not on time. Hyperthyroidism or hypothyroidism patients, may show this phenomenon. 2, because of frequent use of emergency contraception. Emergency contraceptives in the high activity of progesterone, the ovarian secretion of sex hormone function produced a negative feedback effect, so that ovarian secretion function disorder, resulting in menstrual disorders. 3, because of prolonged overeating or excessive diet, for the hypothalamus, pituitary, ovarian axis secretion function produced adverse effects, resulting in menstrual disorders.