Irregular Menstruation

Irregular menstruation is variation in cycle length of more than 7 to 9 days between the shortest and longest cycles over 12 months, with unpredictable timing of periods. It is common in the first 2 years after menarche and in the perimenopause, and otherwise results from polycystic ovary syndrome, thyroid disease, hyperprolactinaemia, stress, weight change, exercise, contraception and structural disease. It matters because it can reflect ovulatory dysfunction, affect fertility and, rarely, signal endometrial pathology.

• Risk factors: adolescence, perimenopause, polycystic ovary syndrome, thyroid disease, weight loss or gain, stress, shift work, recent hormonal contraception.
• Cycle length in adolescents may range from 21 to 45 days in the first years.
• Persistent irregularity beyond 3 years after menarche needs evaluation.

Women have periods of unpredictable timing, with variable flow and duration, sometimes with premenstrual symptoms, spotting or missed periods. Examination may show features of the cause (hirsutism, goitre, galactorrhoea, obesity).

• Menstrual diary with cycles that differ by 8 days or more.
• Normal pelvic examination in most.
• Differential diagnosis: normal adolescent pattern, polycystic ovary syndrome, perimenopause, thyroid disease, hyperprolactinaemia, hypothalamic amenorrhoea, premature ovarian insufficiency, contraceptive effect, pregnancy or miscarriage, endometrial polyp, fibroids, cervical or endometrial cancer, bleeding disorder.
• Complications: infertility, anaemia from heavy bleeds, endometrial hyperplasia, anxiety, missed work or school, unplanned pregnancy.

The approach is a menstrual diary and targeted tests based on age and symptoms.

• Menstrual diary for 3 months; urine hCG; weight, height, body mass index, hirsutism score, blood pressure; abdominal and pelvic examination.
• Thyroid stimulating hormone, prolactin, follicle stimulating hormone, oestradiol, testosterone; full blood count and ferritin.
• Pelvic ultrasound for ovarian morphology and endometrium; day 21 progesterone to confirm ovulation.
• Endometrial sampling or hysteroscopy if age is above 45 years or if there is persistent intermenstrual bleeding or risk factors for endometrial cancer.

The principle is reassurance in adolescents, treatment of the cause in others, and cycle regulation when symptoms or risks need it.

• Supportive: menstrual diary; reassurance that irregular cycles in the first 2 to 3 years after menarche are normal; weight management; stress and sleep care; iron rich diet.
• Pharmacological: cycle regulation: combined oral contraceptive pill with ethinylestradiol 30 micrograms and levonorgestrel 150 micrograms oral once daily for 21 days then 7 days free; medroxyprogesterone 10 mg oral once daily for 10 to 14 days every month for women who cannot use oestrogen; levonorgestrel intrauterine system 52 mg for 5 years for heavy or perimenopausal bleeding; tranexamic acid 1 g oral 8-hourly for up to 4 days during heavy bleeding; mefenamic acid 500 mg oral 8-hourly with food for pain; ferrous sulphate 200 mg oral 12-hourly for 3 months for anaemia; levothyroxine 50 micrograms oral once daily increased every 4 to 6 weeks for hypothyroidism; cabergoline 0.25 mg oral twice weekly for hyperprolactinaemia, increased to a maximum of 1 mg twice weekly; metformin 500 mg oral once daily increased to 500 mg 3 times daily for polycystic ovary syndrome with insulin resistance.
• Procedures: hysteroscopic removal of a polyp or submucous fibroid; endometrial sampling; endometrial ablation for persistent heavy bleeding after childbearing.
• Special groups: adolescents within 2 years of menarche are observed with a diary and treated only for heavy bleeding or anaemia; perimenopausal women prefer the levonorgestrel intrauterine system and have endometrial assessment if bleeding persists; women who cannot take oestrogen (migraine with aura, hypertension, previous clot, smoking above age 35 years) use progestogen-only methods.
• Red flags: haemoglobin below 8 g/dL, bleeding after age 45 years that does not settle, postcoital bleeding, pelvic mass, rapid virilisation, visual loss, weight loss, fever with pelvic pain.
• Follow-up: review at 3 months with menstrual diary and haemoglobin; investigation if irregularity persists beyond 3 years after menarche; endometrial assessment if risk factors; annual review of metabolic risk in polycystic ovary syndrome.