Normally, the maternal and fetal connective tissues become progressively collagenized. Because of the lack of hormonal preparation to the maternal tissue or no estrogen, the connective tissue fibers swell due to the absorption of water by the cells. The opposite can occur if the involution of the placentomes is advanced or rapid. The maternal crypt thickens and holds on to the fetal villi. Edema of the chorionic villi follows a caesarian section or a uterine torsion that has lasted for an extended period of time.
Any infectious agent can cause placentitis or cotyledonitis.
A septicemia from the udder, intestines or feet can be transmitted to the uterus, and the fetal membranes become edematous, necrotic, leathery or hemorrhagic. Necrotic areas can develop between the fetal villi and the crypt wall. Deficiencies in Vitamins A, E and Selenium must be considered. Overweight dry cows have an increased incidence of retained placenta. Endocrine - Hormonal a.