What is the normal thickness of the endometrium before menstruation?

The thickness of the endometrium changes over time, and the thickness of the endometrium is different during different cycles. During ovulation, the endometrium thickens in preparation for the implantation of the fertilized egg. After ovulation and before the onset of menstruation, the endometrium slowly shrinks and becomes thinner. So what is the normal thickness of the endometrium before menstruation?

1. Premenstrual endometrial thickness

The thickness of the endometrium is not fixed but varies periodically. Days 15-28 of the menstrual cycle, which is half a month before menstruation, belongs to the endometrial secretory phase, corresponding to the luteal phase. If there is no fertilization during the luteal phase, the corpus luteum will slowly decline and can no longer secrete progesterone and estrogen. The endometrium will become necrotic, and the luteal phase will enter the menstrual phase.

The menstrual cycle of 15-28 days corresponds to the three secretory phases of the endometrium: early secretory phase, mid secretory phase and late secretory phase. Early secretion is from day 15 to 19 of menstruation; mid secretion is from day 20 to 23; late secretion is from day 24 to 28. The thickness of the endometrium changes with each cycle.

2. Will the endometrium thicken before menstruation?

The endometrium is not a fixed value. Before menstruation, the endometrium is divided into three stages. 15-19 days before menstruation is the early secretion stage of the endometrium. The endometrium will continue to thicken and reach a thickness of 5mm. The endometrial glands become longer and more curved during this period.

During the 20th to 23rd day of the menstrual cycle, which is the mid-stage of endometrial secretion, the endometrium will become thicker and take on a serrated shape; at this time, the endometrial stroma will become loose.

The menstrual cycle is 24-28 days, which belongs to the late stage of endometrial secretion. It is also the time when menstruation is about to come. The endometrium changes from serrated to spongy, with a thickness of 10mm; at this time, the endometrial stroma is looser and filled with water.

Days 1 to 4 of the menstrual cycle. The spongy functional layer of the endometrium falls off from the basal layer, and the contraction of the endometrium causes spasmodic contraction of the blood vessels, which can cause necrosis, deformation, and peeling of the blood vessel walls and tissues. After the endometrium peels off, it flows out of the vagina with the blood, and menstruation occurs. The thickness of the endometrium can reach 8-10mm.