Hormones produced by the ovaries, such as progesterone, are known to play a role in maintaining an early pregnancy before the placenta takes over this important function. It is speculated that in some women, there may be abnormally low levels of these hormones and that oral hormone replacement early in the pregnancy may help avoid miscarriage. Although this theory has not been absolutely proven, providing hormone replacement is widely practiced in the medical community. Other hormone disturbances, such as in diabetes and thyroid disease, can be associated with recurrent miscarriage. Structural abnormalities of the uterus can also cause miscarriages.
Fibroid tumors are benign growths of muscle cells in the uterus.
While most fibroid tumors do not cause miscarriages, some can interfere with the embryo implantation and the embryo's blood supply, thereby causing miscarriage. The septum usually has a very poor blood supply, and is not well suited for placental attachment and growth. Therefore, an embryo implanting on the septum would be at increased risk of miscarriage. Over the past several years, there has been a lot of interest focused on the role of the immune system in pregnancy and miscarriage. The immune system consists of cells and proteins that usually help the body fight infection and remove damaged or abnormal tissue.