Retroflexion and retroversion usually coexist. The conditions are due to similar causes. They may originate simultaneously, or one condition, occurring primarily, may induce the other. An infinite number of degrees of retroversion may exist. For convenience of clinical description three degrees have been described. In the first degree the fundus uteri is directed upward approximately toward the promontory of the sacrum. In the second degree the uterus lies transversely across the pelvis, the fundus and the cervix being at about the same level. In the third degree the retroversion is extreme, and the fundus lies below the level of the cervix (Fig. 88). Retroversion of the uterus is progressive. It usually proceeds from bad to worse. As soon as the downward abdominal pressure begins to act upon the anterior face of the uterus there is a continuous force increasing the retroversion. There are many causes of retroversion and retroflexion. [Illustration: FIG. 88.--Diagram of the degrees of retroversion of the uterus.] The disease may be congenital. Extreme retroflexion has been found in the uterus of the new-born infant. Congenital retroversion and retroflexion may be due to imperfect development, and resulting imperfect invagination of the cervix. The condition may also be caused by arrest of development of the posterior wall of the uterus; the anterior wall thus outgrowing the posterior. Many cases of retroversion undoubtedly originate during girlhood as a result of falls, blows, distortion of the body, or sudden efforts at lifting. The origin of the symptoms may be traced in many cases directly to some such cause. The uterus may be considered to be balanced upon an axis running transversely. Anything that turns the uterus backward, so that the intra-abdominal pressure may act upon the anterior wall, will produce retroversion. It is probable that an over-distended bladder occasionally acts as a cause of retroversion. Retroversion is not at all rare in single women. It is very often discovered soon after the establishment of the menstrual function, the symptoms of the retroversion, which probably occurred during girlhood, first appearing at this time. Retroflexion, on the other hand, except to the slight extent caused by the retroversion, is unusual in single women.