Endocrine problems, such as thyroid disease, are responsible for 15-20 percent of miscarriages; hypercoagulability, an increased tendency to develop blood clots, also causes 15-20 percent; maternal abnormalities in the uterus or cervix cause 10-15 percent; maternal genetic mutation causes 2-5 percent; and in 0.5-5 percent of cases, infection triggers a miscarriage.