Most women who have menstrual cycles will experience abnormal bleeding and blood clots at some point before menopause. While many causes of abnormal menstrual bleeding and blood clots are relatively harmless, all instances of continuous bleeding or passing large blood clots should be investigated by a physician.
Normal Menstrual Cycle
At the time of puberty, girls start a monthly menstrual cycle called a "period." During this monthly cycle, the pituitary gland, located in the brain, secretes luteinizing and follicle-stimulating hormones. The secretion of these hormones send a signal to the ovary to produce two hormones called estrogen and progesterone. The production of these hormones stimulate egg production, which causes a woman's uterine lining (endometrium) to thicken in anticipation of pregnancy. If no pregnancy is achieved, the estrogen and progesterone levels drop, causing the endometrium to shed along with blood. This is considered day one of the menstrual period. A menstrual cycle lasts anywhere from 25 to 36 days with three to seven days of bleeding. During this time, women lose between .5 to 2.5 ounces of blood. It is not unusual in this time for women to pass small blood clots if the bleeding is heavy. In fact, MayoClinic.com internist Dr. Sandhya Pruthi states that passing blood clots during menstruation can be perfectly normal.
Identifying Abnormal Bleeding
Abnormal menstrual bleeding that contains blood clots usually occurs when a woman is bleeding between periods, spotting, bleeding after sex, bleeding heavily, bleeding more than seven days, having a menstrual cycle less than 28 days or more than 35 days apart or bleeding post-menopause.
Uterine Causes
One common cause of abnormal bleeding and clotting is uterine fibroids. Uterine fibroids are small growths that attach to the uterine lining, inside of the lining, or on the outside of the uterus. Although the cause is not known, estrogen seems to fuel their growth--which, when excessive, can cause heavy bleeding. These fibroids mainly affect women over the age of 30, and according to MedlinePlus, as many as one in five women have had them. Heavy bleeding as a result of this condition is treated by the use of birth control pills to regulate the hormones or by using an intrauterine device (IUD) to slowly release progesterone, which lightens the bleeding.
Ovarian Causes
Polycystic ovary syndrome (PCOS) is a condition that affects the way a woman menstruates. The pituitary gland secretes excessive amounts of luteinizing and follicle-stimulating hormones, which causes the ovaries to over-produce progesterone. This causes variations in the menstrual cycle that can contribute to blood clots, male-pattern hair growth, ovarian cysts and hair loss. Abnormal bleeding due to PCOS is treated with the use of progesterone pills, birth control pills or with metformin. These medications are all used to regulate hormone production.
Pregnancy Loss
A miscarriage is the loss of pregnancy before the 20th week. Bleeding during a miscarriage is caused by shifts in the hormones that control menstruation. In these early weeks, some women don't even realize they're pregnant and may believe the bleeding to be an abnormal period. Symptoms of a miscarriage are heavy bleeding, blood clots, abdominal cramping, lower-back ache or foul-smelling discharge. In many cases the bleeding and blood clots will go away once the miscarriage is complete, but in some cases it is necessary to see a doctor for further analysis.
