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Bleeding between periods

Bleeding between periods should not be ignored. Healthy women with normal regular menstrual cycle should have bleeding only once per month – at the end of menstrual cycle (every 22-35 days). Any bleeding outside of this should be considered as abnormal. Several factors can trigger bleeding between periods including:

  • Hormonal fluctuation,
  • Hormonal contraception,
  • Pregnancy,
  • Vaginal infections,
  • Benign tumors or polyps,
  • Cancer.

Bleeding between periods – causes

Hormonal fluctuation

Female reproductive system is well controlled – hormonal fluctuations during menstrual cycle are well known and any disturbances triggered by stress, diseases or any other factors, could lead to irregular bleeding between periods.

Main female hormones (estrogen and progesterone) are permanently regulating whole menstrual cycle. Any hormonal dysfunctions in ovaries, thyroid or adrenal glands can cause bleeding or bloody discharge.

One of common causes for hormonal dysfunctions in women could Polycystic Ovary Syndrome (PCOS) which can cause irregular periods (mainly oligomenorrhea) and irregular bleeding.

Endometriosis is also well known cause for brown discharge between periods.

Hormonal contraception

Hormonal contraception includes birth control pills (combined contraceptives), mini pills (progesteron-only contraceptives), hormonal contraceptive transdermal patches, contraceptive implants (Implanon, Norplant), contraceptive injections (DepoProvera and Noristerat) and some IUDs with hormonal component (Mirena).

Bleeding between periods

Hormonal contraception is most popular type of contraception but unfortunately it has several side effects including bleeding between periods and bloody irregular discharge.

Hormonal contraception mechanism of action always include changes in hormonal cycles – the contraceptive effect is mainly based on inhibition of ovulation, thickening of the cervical mucus, making it difficult for sperm to pass into the uterine cavity and move towards the Fallopian tubes as well as changes in endometrium (uterus internal lining) which decrease chances for fertilized egg implantation.

Irregular bleeding and bloody discharges are common during first three months of starting hormonal contraception. This side effect is also very typical during missed pills and/or missed injections and/or missed patches.

Special attention should be paid to irregularities after emergency contraception which usually lasts few weeks.


Unexpected bleeding is always a subject of concerns during pregnancy (especially during first trimester). Most dangerous cases are miscarriages and ectopic pregnancy – both can cause bleeding. Sometimes women suffer from bleeding after artificial abortion. In all cases urgent medical care is needed.

Vaginal infections

Irregular vaginal bleeding between periods could be a symptom of different types of infections including pelvic inflammatory disease (PID) and sexually transmitted diseases (STDs).

Infections in women reproductive system usually trigger inflammation, irritation, damage of vessels and bleeding or bloody discharge.

Benign tumors or polyps

Uterine fibroids (noncancerous growths of uterus tissue) often cause uterine bleeding. Similar symptoms could be noted during endometrial and cervical polyps (non-cancerous growths in the womb or the lining of the cervix), cervical ectropion and/or cervical erosion.


Cancer is the most dangerous cause of bleeding between periods. All women over 40 with bleeding between periods should eliminate the possibility of cancer in reproductive system – uterine cancer, cervical cancer, ovarian cancer and vaginal cancer.

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