Abnormal uterine bleeding (AUB)—or menstrual bleeding that is unpredictable in timing, amount, or duration—is a common problem among women. This can range from light spotting during or in between menstrual periods, or extremely heavy blood flow during the monthly period.

As part of a woman’s monthly menstrual cycle, the mucous membranes that line the uterus prepare for an egg to be fertilized and settle there. If that doesn’t happen (no egg is fertilized), the body sheds the lining along with some blood. Typically lasting five to seven days, this is what is called your “period.”

Bleeding that occurs at any other time of the month is considered AUB. The usual cause is a hormone imbalance, but other potential causes include structural abnormalities (fibroids, polyps, adenomyosis), anovulation (when ovulation doesn’t occur), and bleeding disorders. Additionally, certain medications or cancer may result in unusual bleeding patterns. The bleeding may be accompanied by disruptive and sometimes debilitating cramping and pain.

Uncomfortable and inconvenient as it is, AUB is quite common—and can usually be treated and managed.

A normal menstrual cycle typically lasts between 21 and 35 days. The cycle begins on the first day of menstruation and extends through the luteal phase, which is when the endometrial layer sheds from the uterus if an egg is not fertilized. A woman’s period generally lasts about five to seven days. If you experience menstrual bleeding during any of the following situations, it‘s considered abnormal:

• Bleeding or spotting between periods
• Bleeding or spotting after sex
• Heavy bleeding during your period
• Bleeding after menopause
• A menstrual cycle lasting longer than 35 days or shorter than 21 days
• Irregular periods, in which the period occurs more frequently than every 21 days and where menstrual bleeding lasts longer than eight days

Abnormal uterine bleeding is most commonly seen in girls who have just started to menstruate, and women in their mid-40s who are nearing menopause. Essentially, the problem is most common at the beginning and end of the reproductive years.

The most common cause of abnormal uterine bleeding is a hormone imbalance (typically, too much estrogen or not enough progesterone). Other causes include the following:

• Ovulation problems, such as polycystic ovary syndrome (PCOS, a condition in which cysts grow on the ovaries, disrupting the balance of hormones)
• Fibroids or polyps, which can interfere with production of the uterine lining
• Adenomyosis, a condition in which endometrial tissue grows into the wall of the uterus
• Miscarriage
• Ectopic pregnancy
• Less commonly, uterine, or other forms of cancer

Abnormal uterine bleeding is a diagnosis of exclusion. This means your doctor will rule out the possible causes of bleeding in order to arrive at the source of the problem.

Your Ob/Gyn will begin by taking a detailed medical history and performing a physical exam. He or she may also order imaging studies and lab tests.

At Yale Medicine, we have state-of-the-art imagine technology for pelvic magnetic resonance imaging (MRI) scans and sonohysterograms. With this type of ultrasound, a thin plastic tube is used to inject sterile saline solution into the uterus. Sound waves are then used to create images of the lining of the uterus—the fluid inside the uterus helps show more details than can be seen with a standard ultrasound.

To rule out blood diseases and sexually transmitted infections (STIs), your provider may also order blood tests to check your blood count and hormone levels. In some cases, the doctor may perform a biopsy to check for the presence of cancer.

There are various therapies available, depending on the cause of abnormal bleeding. If you’re diagnosed with an ovulatory dysfunction, for example, the first-line treatment is usually hormonal regulation of the menstrual cycle. To help regulate periods and lighten menstrual flow, you doctor may also prescribe a form of birth control. These include the pill, skin patches, vaginal rings, and progesterone-containing IUDs.

If medication doesn't help or if a structural abnormality is present, you may need surgery. There are several different options: Minimally invasive surgery for hysterectomy (removal of the uterus), endometrial ablation (heat, cold, or energy is used to destroy the uterine lining), or robotic surgery for anatomic abnormalities (such as fibroids) may also be offered.

Our physicians are double board-certified in obstetrics-gynecology and in reproductive endocrinology and infertility. They specialize in the use of evidence-based treatments for abnormal uterine bleeding. Because treatments are always evolving, our physicians are also actively engaged in conducting research to determine new and more effective ways to treat this condition.