The menstrual cycle and fertility control — Edexcel GCSE Biology
The stages of the menstrual cycle, the hormones that control it, contraception, and IVF and clomifene.
Revision notes
5 short notes, in the order of the specification. Each one in short:
The menstrual cycle is a series of changes in a woman that repeats about every 28 days. The uterus lining breaks down in menstruation (days 1 to 5), is repaired and thickens, an egg is released at ovulation around day 14, and the lining is then maintained. Oestrogen repairs the lining and progesterone maintains it.
How four hormones control the cycle
Higher tierThe menstrual cycle is controlled by four hormones: FSH and LH from the pituitary gland, and oestrogen and progesterone from the ovaries. FSH makes an egg mature and stimulates oestrogen production. High oestrogen inhibits FSH and stimulates the release of LH, which causes ovulation. Progesterone maintains the uterus lining and inhibits FSH and LH.
Hormonal contraceptives contain oestrogen, progesterone or both, given as a pill, patch, injection or implant. They keep hormone levels high, so eggs do not mature and ovulation does not happen. Progesterone also makes the mucus at the cervix thicker, so sperm cannot get through to reach an egg. The pill does not kill sperm.
Barrier methods such as condoms and diaphragms stop sperm reaching an egg, while hormonal methods change the menstrual cycle. Hormonal methods are very effective when used correctly, but they do not protect against sexually transmitted infections and can cause side effects. Condoms do protect against these infections, but they are less effective if not used correctly.
Assisted reproductive technology
Higher tierAssisted reproductive technology uses hormones to help people who find it hard to have a baby. In IVF, the woman is given FSH and LH so several eggs mature; the eggs are collected, fertilised by sperm in a dish, and one or two embryos are placed in her uterus. Clomifene stimulates the release of FSH and LH so ovulation happens.
Exam questions
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Quick check questions
Which hormone repairs the uterus lining and which maintains it?
Show answer
Oestrogen repairs it. Progesterone maintains it.
Around which day does ovulation happen in a 28-day cycle?
Show answer
Around day 14.
State one way the contraceptive pill prevents pregnancy.
Show answer
It stops ovulation, or thickens the mucus at the cervix so sperm cannot get through.
Give one advantage of condoms over the pill.
Show answer
They protect against sexually transmitted infections.
What does clomifene do? (Higher)
Show answer
It stimulates the release of FSH and LH so that ovulation happens.
Frequently asked questions
What happens during the menstrual cycle?
The menstrual cycle repeats about every 28 days. On days 1 to 5 the uterus lining breaks down and is lost in menstruation. From day 5 to 14 oestrogen repairs the lining and it thickens. An egg is released at ovulation around day 14, then progesterone maintains the lining until day 28, ready for a fertilised egg.
What does FSH do in the menstrual cycle?
Higher tier FSH, released by the pituitary gland, causes an egg to mature in an ovary and stimulates the ovaries to produce oestrogen. As oestrogen rises it inhibits FSH and stimulates the release of LH, which causes ovulation. After ovulation, progesterone inhibits FSH and LH, so no more eggs mature while the uterus lining is maintained.
How do contraceptive pills prevent pregnancy?
Contraceptive pills contain oestrogen, progesterone or both, which keep hormone levels high. This stops eggs maturing, so ovulation does not happen and there is no egg to fertilise. Progesterone also makes the mucus at the cervix thicker, so sperm cannot reach an egg. The pill does not kill sperm or stop sperm being made.
What are the advantages and disadvantages of condoms and the pill?
The pill is very effective when taken correctly, but it must be taken at the right time every day, can cause side effects and does not protect against sexually transmitted infections. Condoms do protect against these infections and have no hormone side effects, but they are less effective if not used correctly, for example if one splits.
How does IVF work?
Higher tier In IVF, the woman is given FSH and LH so that several eggs mature in her ovaries. The eggs are collected and mixed with sperm in a dish in the laboratory, where they are fertilised. The fertilised eggs develop into embryos, and one or two embryos are placed into the woman's uterus. Fertilisation happens outside the body.
Written and checked against the Edexcel GCSE Biology (1BI0) specification · Updated October 2026