Contraception

This lesson covers the different methods of contraception as required by the AQA GCSE Combined Science Trilogy specification (8464). You need to be able to describe hormonal and non-hormonal methods, explain how they work, and evaluate their advantages and disadvantages.

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What Is Contraception?

Contraception means preventing pregnancy. There are two broad categories of contraception:

1. Hormonal methods — use hormones to prevent pregnancy.
2. Non-hormonal methods — use barriers, devices, or other approaches to prevent pregnancy.

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Hormonal Methods of Contraception

Hormonal contraception works by altering the natural hormone levels to prevent pregnancy. The main mechanisms are:

• Preventing ovulation (no egg is released).
• Thickening cervical mucus (sperm cannot reach the egg).
• Thinning the uterus lining (fertilised egg cannot implant).

Types of Hormonal Contraception

Method	Description	How It Works
The combined pill	Contains oestrogen and progesterone; taken daily	Inhibits FSH release → prevents egg maturation; inhibits LH → prevents ovulation
The progesterone-only pill	Contains only progesterone; taken daily	Thickens cervical mucus; may inhibit ovulation
The contraceptive injection	Progesterone injected every 8–13 weeks	Prevents ovulation; thickens cervical mucus
The contraceptive implant	Small rod inserted under the skin of the upper arm; lasts up to 3 years	Slowly releases progesterone; prevents ovulation
The contraceptive patch	Worn on the skin; replaced weekly	Releases oestrogen and progesterone through the skin
The hormonal IUS (intrauterine system)	Small device placed in the uterus; lasts 3–5 years	Releases progesterone; thins uterus lining; thickens cervical mucus

Exam Tip: The combined pill contains both oestrogen and progesterone. Oestrogen inhibits FSH, preventing egg maturation, which is why no ovulation occurs. This directly links to what you learned about hormone interactions in the menstrual cycle.

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Non-Hormonal Methods of Contraception

Method	Description	How It Works
Condoms (male)	Thin latex sheath worn over the penis	Physical barrier — prevents sperm reaching the egg; also protects against STIs
Condoms (female / internal)	Thin pouch inserted into the vagina	Physical barrier — prevents sperm reaching the egg
Diaphragm / cap	Dome-shaped barrier placed over the cervix (used with spermicide)	Physical barrier — prevents sperm entering the uterus
IUD (intrauterine device / copper coil)	Small copper device inserted into the uterus; lasts 5–10 years	Copper is toxic to sperm; also prevents a fertilised egg from implanting
Spermicide	Chemical cream, gel, or foam applied inside the vagina	Kills or disables sperm
Natural family planning	Monitoring body temperature, cervical mucus, and cycle dates to identify fertile days	Avoiding intercourse on fertile days (around ovulation)
Surgical methods (sterilisation)	Vasectomy (male) or tubal ligation (female)	Permanently prevents sperm or eggs from reaching the reproductive tract
Abstinence	Not having sexual intercourse	No chance of sperm meeting egg

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Advantages and Disadvantages

Method	Advantages	Disadvantages
Combined pill	Very effective (~99%); regulates periods	Must be taken daily; side effects (headaches, mood changes); does not protect against STIs
Condoms	Protects against STIs; no hormonal side effects; widely available	Must be used every time; can break or slip; slightly less effective than hormonal methods
Implant	Very effective (~99%); lasts up to 3 years; no daily action needed	Requires minor procedure; can cause irregular bleeding; does not protect against STIs
IUD (copper coil)	Non-hormonal; lasts 5–10 years; very effective	Can cause heavier periods; does not protect against STIs
Natural family planning	No hormones or devices; no side effects	Less reliable; requires careful monitoring; does not protect against STIs
Surgical (sterilisation)	Permanent; very effective	Difficult to reverse; surgical risks; does not protect against STIs

Exam Tip: A common exam question asks you to evaluate different contraceptive methods. Make sure you give both advantages and disadvantages, and mention whether the method protects against STIs (only barrier methods like condoms do).

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Choosing a Contraceptive Method

The choice of contraceptive method depends on several factors:

• Effectiveness — how reliable is the method?
• Convenience — how easy is it to use?
• Side effects — does it cause unwanted effects?
• STI protection — does it protect against sexually transmitted infections?
• Reversibility — can the person become pregnant after stopping the method?
• Personal preference — some people prefer non-hormonal methods; others want long-lasting methods.

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Common Mistakes

• Saying the pill prevents fertilisation — the pill primarily prevents ovulation (no egg to fertilise). It does not act as a barrier.
• Forgetting that only barrier methods protect against STIs — hormonal methods, IUDs, and natural methods do not protect against sexually transmitted infections.
• Confusing the IUD (copper coil) with the IUS (hormonal coil) — the IUD is non-hormonal (copper); the IUS releases progesterone.
• Not explaining the mechanism — in the exam, always explain how the method works, not just what it is.

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Summary

• Contraception prevents pregnancy using hormonal or non-hormonal methods.
• Hormonal methods (e.g. the pill, implant, injection) primarily work by preventing ovulation or thickening cervical mucus.
• Non-hormonal methods (e.g. condoms, IUD, diaphragm) act as barriers or make the uterus inhospitable to sperm.
• Only barrier methods (condoms) protect against STIs.
• When evaluating methods, consider effectiveness, convenience, side effects, STI protection, and reversibility.
• This is assessed in AQA GCSE Combined Science Trilogy (8464), Paper 1: Biology.

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Extended Examples and Exam Technique

Extended Worked Example — Evaluating Methods

A couple are considering contraception. Compare the advantages and disadvantages of the combined oral contraceptive pill and the use of condoms. [6 marks]

Model answer: