Sometimes a thyroid problem causes bleeding. These are just a few of the problems that can cause abnormal uterine bleeding. These problems can occur at any age. But the likely cause of abnormal uterine bleeding depends on your age. A common cause of abnormal bleeding in young women and teenagers is pregnancy.
Many women have bleeding in the first few months of a normal pregnancy.
Birth control pills or the Norplant birth control device can also cause abnormal bleeding. In the years before menopause, women have months when they don't ovulate. This can cause abnormal uterine bleeding. This thickening can be a warning of uterine cancer. In women in their 40s and early 50s, it's important to make sure uterine cancer isn't the cause of abnormal bleeding.