Clinical meaning
The uterus is a hollow muscular organ situated in the pelvic cavity between the bladder and the rectum. In its non-pregnant state, the uterus weighs approximately 60 grams and measures approximately 7.5 centimeters in length. During pregnancy, the uterus undergoes remarkable changes driven by estrogen and progesterone: it increases in weight to approximately 1000 grams (a 16-fold increase), its capacity increases from 10 mL to 5000 mL or more, and its blood flow increases from 50 mL per minute to approximately 500 to 700 mL per minute at term. The uterine wall consists of three layers: the endometrium (inner mucosal layer, which becomes the decidua during pregnancy), the myometrium (thick muscular middle layer composed of smooth muscle cells arranged in interlocking bundles), and the perimetrium (outer serosal layer continuous with the peritoneum). The myometrium is the thickest layer and is responsible for the powerful contractions of labor. The unique figure-of-eight arrangement of myometrial muscle fibers surrounding blood vessels is critical to understanding postpartum hemostasis: when these fibers contract after placental delivery, they compress the blood vessels that supplied the placental...