|Cyclical occurrence in a female of reproductive age
||Menstruation in normal fertile females happen in regular cycles. The length of a normal cycle is usually between 21 and 35 days. A cycle that comes in the length of less than 21 days is called epimenorrhea or polymenorrhea, whereas the length of more than 35 days is called oligomenorrhea. [1, 2, 3, 4] The first half of each cycle is known as the follicular phase. In this phase, few ovarian follicles start to develop from one ovary under the influence of pituitary gonadotrophins. During the intercycle rise of follicle-stimulating hormone (FSH), selection of the dominant follicle takes place. At the same time, luteinizing hormone (LH) stimulates the synthesis of androgens, which serve as the substrate for the production of estrogens. Meanwhile other sex steroids are low. At ovulation luteinizing hormone and follicle-stimulating hormone surges are associated with falling estrogen levels, this is usually in the 14th day of the cycle. Secretions of progesterone and estrogen again are characteristic of the second half of menstruation or the luteal phase, which is followed by menstrual bleeding. [5, 6, 7, 8, 9, 10, 11]
||It's a wide range of symptoms that happens in the second half of the menstruation and disappears after a day or two following the start of menstrual bleeding. The definite cause for this is unknown but it is hypothesized that the change in sex hormones during the second half of the menstrual cycle is responsible for it. The females feel vague symptoms of varying intensity. (i.e. bloating, headache, mood changes, constipation or diarrhea, fatigue) [12, 13, 14, 15, 16, 17]
|Mid-cycle pain and bleeding
||Known as mittelshmerz, this brief unilateral mid-cycle pain is indicative of ovulation happening. There can be spotting associated with ovulation also. [18, 19, 20, 21, 22, 25, 26, 27]
||The normal vaginal discharge is white, nonhomogeneous, and viscous. It contains vaginal squamous epithelial cells in a serous transudate, as well as material from sebaceous, sweat, and Bartholin's glands, and secretions from the cervix. Mucus spinnbarkeit, ferning, and wet weight are associated with the ovulatory phase of the menstrual cycle. The maximum mucus secretion is associated with ovulation. [28, 29, 30]
||The functional layer of the endometrium shows steroid hormone-dependent proliferation, differentiation, and shedding in the absence of the trophoblast. When the ovum is not fertilizede, menstrual bleeding is initiated by progesterone responsive decidual cells, and executed by PGE and PGF2α, vasoconstriction and matrix metalloprotease secretion by leukocytes.  The amount of mentrual fluid at each cycle should be less than 80 ml in volume, more than that is called menorrhagia.  The first menstrual bleeding is considered as the hallmark of a girl's puberty achievement. The first few menstrual cycles may not be regular, and they are usually anovulatory.  Irregularity of menstruation is observed also near menopause.