A normal menstrual cycle lasts anywhere between 25 to 36 days. During this cycle, bleeding should only occur in this first week for three to seven days. However, some women may experience light brown bleeding in between periods known as spotting. There are many causes for spotting, some normal and others requiring medical attention.
Midway through a woman's menstrual cycle, levels of the hormones estrogen and progesterone rise causing a follicle within the ovary to release an egg. When this egg is fertilized and has reached the blastocyst stage, it will attach to the uterine lining. During this time, some women may know that they are pregnant; however, other women may feel slight abdominal pain and may bleed a little. This bleeding is called implantation bleeding and it may be pink, red or brown in color. Implantation bleeding is normally very light and may only require a woman to wear a pantyliner for protection.
Ovulation spotting occurs at the time a woman is ovulating. This bleeding normally occurs midway through a woman's menstrual cycle. As of 2010, the causes of ovulation spotting are unknown, but according to MayoClinic.com, it may be due to the ovary surface stretching or slight bleeding from the follicle rupturing within the ovary and irritating the abdominal lining. Ovulation spotting lasts just a few days and the bleeding is normally very light. Also during this time, a woman may experience light cramping on one side of the abdomen, this is known as mittelschmerz or middle pain.
Uterine fibroids are benign uterine growths that form in the uterine muscle, uterine lining and the uterine cavity. Uterine fibroids can be microscopic or large enough to weigh several pounds and completely fill the uterine cavity. The causes of uterine fibroids are unknown, however it is known that they are estrogen sensitive. This means that a woman who has developed uterine fibroids will continue to have them or they will continue growing until the stage of menopause. Uterine fibroids cause heavy menstrual bleeding, bleeding between menstrual cycles, pelvic pressure, pelvic pain, constipation, backache and leg pain. As many as 75 percent of women will develop uterine fibroids at some point in their reproductive years, the Mayo Clinic notes.