What is abnormal uterine bleeding and when should I worry?

Most women have menstrual cycles that last about 28 days on average, but this can vary between 24-34 days. Your period, when there is a blood flow, will usually be from 4 to 7 days at the beginning of the cycle. However, each woman's cycle is different and unique to her.

Expected variations in periods

In the first few years of having periods, the amount of blood loss may not always be the same and it can change with each cycle from light to very heavy. The cycles can range from 21 to 45 days apart until the main hormone levels (oestrogen and progesterone) stabilise, and ovulation - when your egg is released - becomes regular.

Light blood spotting - a very small amount of bleeding - for a few days before menstruation starts is common. Birth control pills (hormonal contraception) may cause occasional blood spotting or breakthrough bleeding - bleeding whilst taking the pills - in the first few months of taking them¹.

Coils, including the copper coil and those containing progestogens, such as the Mirena, can also cause irregular bleeding during the first months after insertion - as can the contraceptive implant. The Mirena is often used to help women with heavy bleeds as it can reduce them or stop periods all together in some people.

In the years leading up to menopause (perimenopause), hormone levels fluctuate again and then go down. So periods may become heavier, then lighter, then spaced further apart or become irregular before they eventually stop.

Abnormal uterine bleeding

Abnormal uterine bleeding means you bleed for longer than you usually do or when you are not expecting it. It can occur regularly or irregularly throughout a cycle and may happen often or only from time to time. You can bleed:

• Between your periods - intermenstrual bleeding.

• After sexual intercourse - postcoital bleeding.

• For shorter or longer than is usual for you.

• Heavier and have clots or flooding.

• After menopause - postmenopausal, after 12 months of not having had a period.

What causes abnormal uterine bleeding?

There is a long list of possible causes of abnormal vaginal bleeding, so it's essential to see your doctor or healthcare professional². They will likely check for, or refer you to a specialist to investigate:

• Cancer of the cervix - the endometrium lining of the uterus, ovaries or vagina.

• Endocrine causes - such as thyroid problems, and Polycystic Ovary Syndrome (PCOS).

• Infections - such as inflammation of the cervix (cervicitis), chlamydia, gonorrhoea, pelvic inflammatory disease (PID), and inflammation of the lining of the womb (endometritis) or vagina (vaginitis).

• Medical conditions - such as kidney and liver disease, coeliac disease, or blood clotting disorders.

• Non-cancerous growths in the cervix, uterus, or endometrium - such as polyps and fibroids.

• Fluctuating hormone levels - cycles where there is no ovulation (anovulatory cycles).

• Pregnancy and complications of pregnancy - such as ectopic pregnancy or miscarriage.

• Trauma to the cervix or vagina through rough sex or sexual abuse.

• Withdrawal bleeding - relating to stopping or changing birth control pills, menopausal hormone therapy, or as a side effect of certain drugs such as tamoxifen.

• Hormonal changes due to perimenopause.

• Genitourinary syndrome of menopause - which can cause vaginal atrophy, a dryer, less elastic, less lubricated vagina due to lack of oestrogen.

• Weight - being overweight can contribute to a thickening of the lining of the womb (endometrial hyperplasia) .

Postmenopausal abnormal bleeding

What can help with abnormal uterine bleeding?

There are several different treatments that can help abnormal bleeding - these include:

• Taking hormones.

• Stopping hormones.

• Having a coil.

• Non-steroidal anti-inflammatory medicines - such as mefanamic acid or ibuprofen.

• Tranexamic acid.

• Endometrial treatments for conditions such as endometriosis.

• Surgery.

Further reading

1. FSRH: Problematic bleeding with hormonal contraception.

2. National Institute for Health and Care Excellence:Heavy menstrual bleeding: assessment and management.

3. UpToDate: Approach to the patient with postmenopausal uterine bleeding.