Idiopathic Nonmenstrual Bleeding (Unexplained Bleeding Between Periods)

What counts as nonmenstrual bleeding

A typical menstrual cycle is 24 to 38 days, with bleeding lasting up to 8 days. Nonmenstrual bleeding is any bleeding outside that pattern:

• intermenstrual bleeding: spotting or bleeding between periods
• postcoital bleeding: bleeding after sex
• postmenopausal bleeding: bleeding after periods have stopped, which always needs evaluation

Doctors classify causes of abnormal uterine bleeding using the PALM-COEIN system:

"Idiopathic" bleeding usually falls into the endometrial or "not otherwise classified" groups once everything else is excluded.

Causes that must be ruled out

• pregnancy-related: implantation bleeding, miscarriage, ectopic pregnancy
• ovulation spotting: light mid-cycle bleeding from the hormone dip at ovulation, common and harmless
• hormonal contraception: breakthrough bleeding is very common in the first 3 to 6 months of pills, implants, injections and hormonal IUDs, and with missed pills
• infections: cervicitis from chlamydia or gonorrhea, pelvic inflammatory disease
• cervical polyps and endometrial polyps
• fibroids, especially those growing into the uterine cavity
• ovulation disorders: PCOS, thyroid disorders, high prolactin, perimenopause
• endometrial hyperplasia and endometrial cancer
• cervical precancer or cancer, especially with bleeding after sex
• bleeding disorders such as von Willebrand disease, and blood thinners
• vaginal atrophy after menopause
• trauma or a foreign body

Diagnosis

1. History: cycle pattern, timing of bleeding, contraception, sexual history, medicines, symptoms of thyroid disease or bleeding disorders.
2. Pregnancy test.
3. Pelvic exam including a speculum exam of the cervix.
4. STI testing for chlamydia and gonorrhea.
5. Cervical screening (Pap and/or HPV test) if due.
6. Blood tests: blood count, thyroid function, and sometimes prolactin or clotting tests.
7. Transvaginal ultrasound to look for polyps, fibroids and thickened lining.
8. Endometrial biopsy for people 45 and older, and younger people with risk factors (obesity, PCOS, persistent unopposed estrogen) or failed treatment.
9. Saline sonohysterography or hysteroscopy to look inside the uterus for small polyps.

If all of these are normal, the bleeding may be considered idiopathic.

Why bleeding happens without a clear cause

Even without structural disease, the uterine lining can bleed irregularly because of:

• minor fluctuations in estrogen and progesterone between cycles
• subtle problems with how the lining repairs itself and controls local blood vessels
• sensitivity to stress, weight change, exercise or travel

Many episodes are self-limiting, especially around adolescence and perimenopause.

Treatment

When serious causes are excluded, treatment depends on how bothersome the bleeding is and whether you want contraception or pregnancy:

• Reassurance and monitoring: a bleeding diary for a few cycles.
• Combined hormonal contraceptives: stabilize the lining and cycle.
• Levonorgestrel IUD: very effective at reducing irregular and heavy bleeding.
• Oral progestins, cyclic or continuous.
• Tranexamic acid or NSAIDs during heavier bleeding episodes.
• Adjusting contraception if breakthrough bleeding persists beyond 3 to 6 months.
• Treating anemia with iron if needed.

Re-evaluation is recommended if bleeding changes, worsens or persists despite treatment.

Frequently asked questions

What is idiopathic nonmenstrual bleeding?

It is vaginal bleeding that occurs outside your normal period, where doctors have checked for and ruled out pregnancy, infection, polyps, fibroids, hormone problems, medicines, bleeding disorders and cancer. Idiopathic means no specific cause has been found.

Is bleeding between periods serious?

Often it is not. Mid-cycle ovulation spotting and breakthrough bleeding on hormonal contraception are common and harmless. But it can signal infection, polyps, pregnancy complications or, less often, precancer or cancer, so persistent bleeding should be checked.

What tests are done for bleeding between periods?

Typical tests include a pregnancy test, pelvic exam, STI swabs, cervical screening, blood tests for anemia and thyroid problems, and a transvaginal ultrasound. An endometrial biopsy or hysteroscopy may be needed, especially over age 45.

How is unexplained bleeding between periods treated?

If nothing serious is found, treatment may be simple monitoring, hormonal contraception, a levonorgestrel IUD, progestin tablets, or tranexamic acid. Iron is given if bleeding has caused anemia.