Clinical Management of Pregnancy Complications in the Cow

Abstract

Vandeplassche noted that even if uterine instability is accepted as a cause of torsions up to 180°, it does not explain those torsions of 360° or more. I concur with this statement and would argue that although uterine instability and all the other predisposing factors may be involved in the development of uterine torsion, there must be some active force which is present in the first stage of labor. It has been proposed that strong fetal movements during parturition may increase the chances of a uterine torsion occurring. First stage labor is associated with particularly vigorous fetal movements presumably invoked by the myometrial contractions and subsequent changes in intra-uterine pressure and fetal blood flow. I believe that it is not so much the violence of the fetal movements as it is the size of the fetus involved. Our data strongly suggests that fetal size is a major factor in the development of uterine torsion. In the normal parturient process the fetus is able to rotate and flex its limbs within the confines of the uterine walls. It is possible that in cases with oversized fetuses the fetal limbs actually catch on the uterine wall and the continued vigorous movements rotate the entire uterus. Although the incidence ofleft side torsions correlates well with the expected incidence of right horn pregnancies, it is interesting to postulate that the preponderance of left side torsions may actually be due the limbs of a large fetus bracing against the rumen wall and "walking'' the uterus down to the left. Another potential traction point is the strong prepubic tendon directly below the uterus. An alternate explanation is that right side torsions may often self-correct. However, if a left side torsion develops, the uterus may become trapped by the rumen. Uterine torsion is ultimately of fetal origin, and there is no evidence to suggest that an affected animal is predisposed to the condition in subsequent pregnancies.