What causes women's hair to fall out?

According to WebMD, androgenic alopecia, or female pattern hair loss, is a common cause of hair loss in women, affecting nearly 50 percent of all women at some point. Other causes of hair loss in women include pregnancy, thyroid disorders, autoimmune diseases, extreme stress, physical trauma, surgery and weight loss.

According to the American Academy of Dermatology, it is normal for women to lose 50 to 100 hairs each day, and on days when shampooing, losing up to 250 hairs can be normal. Losing more hair than this, along with visual cues, such as a general thinning of hair on the top half of the scalp or an increase in the size of a part, indicate a problem, states WebMD.