Women’s stomach bulging before menstruation is a normal situation, because women before menstruation, the body progesterone will appear changes, prompting the uterus distension as well as endothelial thickening, in the pre-menstrual period can be manifested in the phenomenon of the stomach bulging. Normal female menstruation is after ovulation, the egg is not fertilized within 14 days, the corpus luteum atrophies and stops, and begins to secrete estrogen and progesterone, the blood vessels of the endometrium contract, and the endometrium necrotic, shedding causes bleeding, thus forming menstruation. 5-14 days before the formation of menstruation, the proliferative phase of the endometrium to prepare for the fertilization and bedding of the egg, the endometrium will be frequent, repeated proliferation and expansion of the endometrium, estrogen to promote the thickening of the endometrium, 15-28 days of secretion phase of the endometrial cells will be more and more enlarged, the combined effect of estrogen and progesterone after ovulation can make the endometrium undergo edema, the gland produces a large amount of fluid and glycogen, the thickness of the endometrium from 1mm can be Thickening to 6mm, this time for the physiological role of the uterus, in order to prepare for the fertilization of the egg, will lead to the uterus in this period of distension, coupled with the hormone level after the role of the increase in appetite, meal size, as well as the feeling of tiredness, rest and other manifestations, so the body will also have fat deposition, but also feel the stomach bulging. Before menstruation due to pelvic organ congestion, women may be conscious of the lower abdomen and lumbosacral drop, and intestinal dysfunction will produce nausea, diarrhea, constipation and a series of uncomfortable symptoms, 14 days after the corpus luteum once atrophied, the egg is not fertilized, estrogen and progesterone levels will decline, then the endometrial vasoconstriction, the endometrium will bleed if it is dislodged, and the phenomenon of the tummy bulge will also disappear.