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Menstrual irregularity in women of childbearing age is incredibly common, with a prevalence of up to 34 per cent in some areas of the world. Irregular menstruation is common in the extremes of reproductive age, i.e. at menarche and menopause; however during childbearing years, periods tend to follow a regular pattern, occurring on average every 26-29 days.

New-onset irregular menstrual bleeding has a number of aetiologies, and requires careful history-taking, examination and investigation to delineate the cause.

Definition

The definition of irregular menstruation includes oligomenorrhoea (fewer than eight menstrual cycles per year), short cycles (less than 21 days) and long cycles (greater than 35 days). It can also include intermenstrual bleeding (IMB), and post-coital bleeding (PCB).

Some variation in menstrual cycle length is normal, and variation of up to eight days is considered normal and does not require investigation in the absence of any other concerns.

History

It is important to gain an accurate menstrual history, including the last menstrual period (LMP), the frequency, regularity and duration of menses, and the onset of the irregularity. A sexual history should be obtained, including risk of sexually transmitted infection (STI), pregnancy and use of contraception.

Contraceptive use is of particular importance as most types of hormonal contraception are associated with irregular bleeding, particularly progestogen-only methods such as the progestogen-only pill, implant, injection and hormonal coil. Irregular bleeding associated with hormonal contraceptive use need not be extensively investigated.

A brief medical history should be elicited, focusing on potentially contributory conditions such as clotting disorders or hormonal conditions, recent changes to health, or commencement of new medications.

Examination

All women presenting with new menstrual irregularity should have a physical examination, including bimanual examination. This is to confirm the source of bleeding as vaginal, to assess for uterine abnormalities, and to inspect for signs of infection or abnormalities of the cervix.

A general examination may also reveal signs suggestive of an underlying medical condition such as thyroid abnormalities or hirsutism which may cause irregular bleeding.

Investigations

Pregnancy should be excluded in all women, and testing for genital infection is indicated in most cases, as STIs such as chlamydia are one of the most common causes of irregular bleeding. Further tests may include co-testing for human papilloma virus (HPV) and cervical cytology, blood tests (e.g. full blood count, thyroid function tests and coagulation screen), pelvic ultrasound scan to assess for structural abnormalities such as polycystic ovaries or fibroids.

In cases where malignancy is suspected, referral to gynaecology for consideration of colposcopy for cervical abnormalities; or for hysteroscopy or endometrial biopsy for uterine abnormalities.

Differential diagnosis

The differential diagnosis of irregular menstrual bleeding is vast, including:

• Infection, including pelvic inflammatory disease
• Uterine abnormalities such as fibroids, polyps, endometrial hyperplasia
• Hormonal conditions such as polycystic ovary syndrome (PCOS) or hypothyroidism
• Malignancy such as cervical or endometrial cancer
• Hormonal contraceptive use

The role of the primary care practitioner is to carry out preliminary assessment, exclude or treat conditions such as genital infection, provide reassurance, and to identify higher-risk women who require further input from secondary care.

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References

1. BMJ Best Practice (2020). Abnormal Uterine Bleeding. https://bestpractice.bmj.com/topics/en-gb/658
2. Australian Government Department of Health (2020). Managing patients with symptoms of cervical cancer. https://www.health.gov.au/initiatives-and-programs/national-cervical-screening-program/providing-cervical-screening/managing-patients-with-symptoms-of-cervical-cancer#abnormal-vaginal-bleeding
3. Australian Family Physician (2017). The management of irregular bleeding in women using contraception. https://www.racgp.org.au/afp/2017/october/the-management-of-irregular-bleeding-in-women-using-contraception/
4. Cancer Australia (2011). Abnormal vaginal bleeding in pre-, peri- and post-menopausal women: a diagnostic guide for general practitioners and gynaecologists. https://www.canceraustralia.gov.au/sites/default/files/publications/abnormal-vaginal-bleeding-pre-peri-and-post-menopausal-women-diagnostic-guide-general-practitioners/pdf/ncgc_a3_menopause_chart_june_2012_final.pdf
5. The Best Practice Advocacy Centre New Zealand (2019). Investigating and managing abnormal vaginal bleeding: an overview. https://bpac.org.nz/2019/bleeding.aspx
6. The Royal Australian and New Zealand College of Obstetricians and Gynaecologists (2021). Investigation of intermenstrual and postcoital bleeding. https://ranzcog.edu.au/RANZCOG_SITE/media/RANZCOG-MEDIA/Women%27s%20Health/Statement%20and%20guidelines/Clinical%20-%20Gynaecology/Investigation-of-intermenstrual-and-postcoital-bleeding-(C-Gyn-6)-July-2021.pdf?ext=.pdf
7. American College of Obstetricians and Gynecologists (2012). Diagnosis of Abnormal Uterine Bleeding in Reproductive-Aged Women. https://www.acog.org/clinical/clinical-guidance/practice-bulletin/articles/2012/07/diagnosis-of-abnormal-uterine-bleeding-in-reproductive-aged-women
8. American College of Obstetricians and Gynecologists (2013). Management of Acute Abnormal Uterine Bleeding in Nonpregnant Reproductive-Aged Women
9. Managing unscheduled bleeding in non-pregnant, premenopausal women (2013). https://www.bmj.com/content/346/bmj.f3251.long
10. International Journal of Gynecology & Obstetrics (2011). FIGO classification system (PALM-COEIN) for causes of abnormal uterine bleeding in nongravid women of reproductive age. https://obgyn.onlinelibrary.wiley.com/doi/full/10.1016/j.ijgo.2010.11.011