Understanding Ovulation: Four Weekly Lessons

Week 1: Menstruation

Menstruation is the shedding of the uterine lining in women of reproductive age, in response to hormones produced in the brain (by the hypothalamus and pituitary) and the ovaries (Reed, 2018). The hormones are FSH, oestradiol, luteinising hormone and progesterone.

Each month an egg develops, and the lining of the womb is prepared for possible pregnancy. If the egg is not fertilised, it is reabsorbed back into the body and the lining of the womb (the endometrium) is shed. This is known as a period or menstruation (RCOG).

• The phases: menstruation, then follicular, ovulatory and luteal.
• Normal menstruation: periods lasting 2–7 days in a cycle of 21–35 days, with a flow of approximately 25–80 ml (Shaw, 2022). What is normal for each woman varies.
• Abnormal menstruation: irregular, infrequent or absent, prolonged periods, or bleeding between periods. Causes include hormonal imbalance, PCOS and congenital problems.

Painful periods (dysmenorrhoea) can come with vomiting, nausea, diarrhoea, fatigue and headache, and may be associated with irregular or heavy bleeding, vaginal discharge and pain during sex (BMJ). Primary dysmenorrhoea often begins 6–12 months after periods start; endometriosis can be found in adolescents. Secondary dysmenorrhoea occurs years later, and may be linked to fibroids, polyps, endometriosis, adenomyosis or pelvic inflammatory disease.

Week 2: The basics of ovulation

A female is born with all her eggs, but they are small and immature. After puberty, one or two immature eggs mature, or become dominant, each cycle. Ovulation is when a mature egg is released from the ovary. It varies with cycle length, but typically happens around day 14 of a 28-day cycle.

• Follicular phase: from day 1 of bleeding up to ovulation. Immature eggs develop in the ovaries using follicle stimulating hormone and oestrogen.
• Ovulatory phase: a mature egg is released and travels through the fallopian tube to meet sperm, driven by a rise in luteinising hormone, FSH and oestrogen.
• Luteal phase: after ovulation, the body prepares for possible pregnancy. If the egg is fertilised, implantation happens; if not, hormones drop and menstruation starts.

Week 3: Factors that affect ovulation

• Weight: being underweight or overweight can cause irregular or absent periods and irregular ovulation or anovulation.
• Stress: affects how the brain releases and regulates hormones, leading to irregular or absent periods.
• Nutrition: a balanced diet with vitamin D, omega-3 oils and zinc supports ovulation; processed foods and sugars affect insulin and can impair ovulation.
• Exercise and lifestyle: excessive exercise can affect the cycle; alcohol, smoking or drug use can cause anovulation or reduce egg reserve.

Common conditions affecting ovulation include polycystic ovary syndrome (PCOS), thyroid disorders and hyperprolactinaemia. Over- and under-active thyroid affect FSH and LH, and autoimmune thyroid conditions such as Graves’ disease or Hashimoto’s can also disrupt ovulation. Hyperprolactinaemia affects how the brain produces LH and FSH, impairing ovarian function.

Week 4: Monitoring ovulation

• Signs: a rise in basal body temperature, ovulation pain (mittelschmerz), changes in cervical mucus (egg-white, thin, stretchy and slippery), increased libido, and tender breasts.
• Ovulation predictor kits: start from day 10 of a 28-day cycle; with a shorter cycle you may need to start as soon as bleeding stops, around day 7.
• Ovulation tracker apps.

References

• Reed, B.G. and Carr, B.R. (2018) The Normal Menstrual Cycle and the Control of Ovulation. Endotext. MDText.com, Inc.
• Shaw, J.A. (2022) Menorrhagia. Medscape.
• BMJ Best Practice: Dysmenorrhoea.
• NHS Scotland Right Decisions: Menstrual disorders.
• Journal of Clinical Medicine (MDPI), 2023, 12(4):1454.

This guide is for education and support. It does not replace advice from your own doctor or fertility clinic.