The uterus is the female reproductive organ in which the ovum, once it has been fertilized, develops into an embryo then fetus. This organ is shaped like an upside-down pear, and comprises the body of the uterus, rich in blood vessels and lined with the uterine mucosa, or endometrium; and the neck of the uterus that opens onto the vagina
. In order to define the position of the body of the uterus, two angles are taken into account: the angle of flexion, formed between the axes of the body and neck of the uterus; and the angle of version, formed on the pelvic axis, the line drawn from the belly button to the coccyx
. A retroverted, or tilted, uterus is when the angle of version is located behind the angle formed between the belly button and coccyx.