The cause of otosclerosis is not fully understood, although research has shown that otosclerosis tends to run in families and may be hereditary, or passed down from parent to child. People who have a family history of otosclerosis are more likely to develop the disorder. On average, a person who has one parent with otosclerosis has a 25 percent chance of developing the disorder. If both parents have otosclerosis, the risk goes up to 50 percent. Research shows that white, middle-aged women are most at risk. Some research suggests a relationship between otosclerosis and the hormonal changes associated with pregnancy. While the exact cause remains unknown, there is some evidence associating viral infections (such as measles) and otosclerosis.