About once a month, women of childbearing age normal menstruate for 4-6 days, losing between 25 and 60 cc of blood.

The blood is dark in color and mixed with mucous, inflammatory exudate, and cellular debris, representing the shed lining of the uterus.

Day #1 of the menstrual cycle is designated as the first day of the menstrual flow. At approximately Day #14, one or the other ovaries releases an egg (ovulation), an event which may or may not be perceived by the woman.

With ovulation, some women notice brief abdominal cramping while others do not. Some women notice a small amount of pink vaginal discharge or spotting, while others do not. Some women notice a significant, brief, increase in cervical mucous secretions (evidenced in vaginal discharge) but others do not.

Following ovulation, progesterone, the other female hormone (other than estrogen) is produced in significant quantities. Progesterone has a number of functions, but in the normal menstrual cycle, continues to be produced by the ovary for 10-12 days. Following the abrupt fall in progesterone, a new menstrual flow is triggered, starting several days after the drop in progesterone.

Normal bleeding occurs every 26-35 days, lasts 3-7 days, and usually does not involve the passage of blood clots.

Abnormal bleeding is any bleeding occurring outside these normal parameters.