The uterus is a hollow, thick-walled, pear-shaped muscular organ that sits in the true pelvis between the bladder and the rectum. In the non-pregnant state it weighs roughly 60–70 g and measures about 7.5 cm by 5 cm by 2.5 cm; by term it weighs approximately 1,100 g and can accommodate a fetus, placenta, and several liters of fluid. The uterus is the organ of gestation and the engine of labor, so a solid understanding of its regions, layers, and supports is essential to maternal-newborn nursing. The uterus is divided into the fundus (the dome above the points where the fallopian tubes enter, and the landmark for fundal height), the body or corpus, the isthmus (which stretches into the thin lower uterine segment in pregnancy and is the usual site of cesarean incision), and the cervix. Its wall has three layers: the endometrium, where implantation and menstruation occur; the muscular myometrium, whose interlacing fibers act as "living ligatures" that clamp the blood vessels after birth; and the outer perimetrium. Why this matters clinically: Uterine assessment threads through every phase of...