How It Works: How Hormonal Contraception Prevents Pregnancy
Part of Contraception — GCSE Biology
This how it works covers How It Works: How Hormonal Contraception Prevents Pregnancy within Contraception for GCSE Biology. Topic 9: Contraception It is section 5 of 12 in this topic. Use this how it works to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 5 of 12
Practice
15 questions
Recall
20 flashcards
How It Works: How Hormonal Contraception Prevents Pregnancy
For pregnancy to occur, an egg must be released (ovulation), fertilised by a sperm, and then implant successfully in the uterus lining. Hormonal contraception prevents one or more of these steps using synthetic versions of oestrogen and/or progesterone.
The combined oral contraceptive pill (the pill) contains both oestrogen and progesterone. Oestrogen inhibits FSH secretion from the pituitary gland. Without FSH, no egg matures in the ovary — ovulation cannot occur, so there is no egg to fertilise. This is the primary mechanism. Progesterone additionally thickens the cervical mucus, making it more difficult for sperm to reach any egg that might be released. The uterus lining is also thinned, reducing the chance of implantation.
Progesterone-only methods (implant, injection, mini-pill) mainly work by thickening cervical mucus and in some cases suppressing ovulation. Because they do not contain oestrogen, they are suitable for women who cannot take oestrogen for medical reasons.
Non-hormonal methods work differently. Barrier methods physically block sperm from reaching the egg. The copper IUD is toxic to sperm and also prevents implantation if fertilisation occurs. Surgical sterilisation physically severs or blocks the fallopian tubes (female) or vas deferens (male), making egg–sperm meeting impossible.