11 reasons why you might bleed between periods

Dr Juliet McGrattan (MBChB)
·5-min read
Photo credit: Elizabeth Fernandez - Getty Images
Photo credit: Elizabeth Fernandez - Getty Images

From Netdoctor

Bleeding between your periods? It’s common. Of all the women going to see gynaecologists each year, 20 per cent do so because of abnormal bleeding. While most bleeding between periods is harmless, it can sometimes be a sign of an underlying medical condition that needs treatment.

Dr Juliet McGrattan looks at the most common causes of bleeding between your periods:

What is intermenstrual bleeding?

When vaginal bleeding happens unexpectedly between periods it is called intermenstrual bleeding (IMB). Whether it’s only happening occasionally or between every period, you should take steps to find out the cause. If you are experiencing pelvic pain, pain during sex (dyspareunia) or when you get your period it is very heavy, then these are signs that there might be an underlying cause for your IMB.

Bleeding after sex, known as post coital bleeding, is another cause of abnormal bleeding and you should see your GP if this is happening to you.

What causes intermenstrual bleeding?

There are lots of reasons you might be bleeding between your periods. The causes vary with age and serious underlying conditions become more likely as women get older. The following are the 11 most common causes of bleeding between periods:

1. Ovulation

Some women bleed lightly when an egg is released from their ovary. This usually happens around two weeks before a period begins. This can be accompanied by one-sided pelvic pain called mittelschmerz.

2. Pregnancy

Unexpected bleeding can happen in early pregnancy. If there is any possibility at all that you could be pregnant then it’s important to do a test. Sometimes irregular bleeding can indicate an ectopic pregnancy.

3. Sexually transmitted infections

Chlamydia infection is a common cause of IMB. It might be associated with pelvic pain, vaginal discharge and discomfort when passing urine however there may not be any other symptoms. Gonorrhoea is another important infective cause of IMB.

4. Peri-menopause

Bleeding can become irregular and intermittent in the lead up to the menopause when ovulation stops occurring regularly. Knowing what is a period and what is IMB can be tricky. Women over 45 with IMB or under 45 with persistent symptoms should see their GP.

5. Atrophic vaginitis

Vaginal tissue can become thin and delicate around and beyond the menopause due to low levels of oestrogen in the body. This is called atrophic vaginitis and can cause superficial bleeding from the walls of the vagina.

6. Contraception

Bleeding between periods while using a hormonal contraceptive is called breakthrough bleeding (BTB). It is common in the first three to six months of using a new method and is more likely with contraceptives that contain only progesterone. Combined methods that contain oestrogen and progesterone can also cause BTB, particularly if pills are forgotten and missed or the dose of oestrogen is low. Progesterone-containing Intra Uterine Systems (IUS) and copper-containing Intra Uterine Devices (IUDs) are types of coil and both can cause IMB.

7. Medications

Certain medications and herbal products can affect the effectiveness of hormonal contraceptives and therefore cause IMB. Examples include the antibiotic rifampicin, some anti-epileptic medications and St John’s wort. Women who take medication to thin their blood (anticoagulants) are also more likely to experience IMB.

8. Cervical ectropion

Cells that are usually deeper inside the cervix can appear on the outer surface. They are softer and more delicate and can cause IMB and post-coital bleeding. Cervical ectropion is more common in women who are pregnant and in those using contraception that contains oestrogen. Areas of ectropion do not turn into cancer.

9. Polyps

Polyps which are overgrowths of tissue, can develop in lots of places in the body. Those growing from the cervix, vagina and endometrium (lining of the womb) can cause IMB. Polyps are usually benign and harmless but some have the potential to become cancerous in some women.

10. Fibroids

Fibroids are growths of muscle tissue in the wall of the uterus (womb) and around a quarter of women have fibroids. They are more common in black women.

Half of women with fibroids have symptoms which include heavy periods, pain and IMB. Fibroids are not cancerous.

11. Cancers

IMB can be caused by cancer of the cervix, endometrium and by some ovarian cancers too. Cervical cancer is very rare before age 20 and is most common between 35 and 45. Endometrial cancer is most common in women who are beyond the menopause (postmenopausal).

Photo credit: Getty Images
Photo credit: Getty Images

Diagnosis of intermenstrual bleeding

If you’re experiencing IMB from an unknown cause, then it’s important to see your doctor. After asking you lots of questions about your bleeding and general health the doctor will need to examine you. You will be offered a chaperone to be with you during the examination.

The doctor will gently feel your abdomen from the outside and then perform a vaginal examination, first with a finger and then with a speculum. This is a device that is inserted into the vagina. Opening up the speculum allows the doctor to see the cervix which is important for establishing the cause of bleeding.

Tests for intermenstrual bleeding

There are a variety of tests that might be done to work out what is causing IMB. A referral to a gynaecologist might be arranged if the cause of the bleeding is unclear or a specialist opinion is needed. Further more specialised tests and procedures may be carried if appropriate. Intermenstrual bleeding tests include:

  • Vaginal swabs - to rule out infection.

  • Cervical screening (smear) test - if it is due, to look for abnormal cervical cells.

  • Blood tests - to rule out anaemia if bleeding is heavy.

  • Ultrasound scan - to look for fibroids and check ovaries.

  • Colposcopy - a detailed examination of the cervix.

  • Hysteroscopy - looking inside the uterus with a camera.

  • Biopsies - taking tissue samples to look at under a microscope.

Treatment for bleeding between periods

The treatment for IMB varies according to the cause. If no cause is found, then treatment may not be required at all. It is however vital to establish the cause so important conditions such as pregnancy, infection and cancer can be treated appropriately.

If the IMB is found to be as a result of breakthrough bleeding from a contraceptive, alternative products can be tried if the bleeding doesn’t settle over time.

Last updated: 23-12-2020

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