This is a hair loss type that can be caused by many factors to include childbirth, severe illness, medication, hormones or dieting.
There tends to be a sudden reduction in volume as opposed to patchy hair loss. Of course, like all types of female hair loss it is distressing but it does tend to correct itself after a number of months.
If you are worried about your hair then you should consider visiting a registered consultant trichologist who will be in a position to advise as to what is the best course of treatment for your hair.