Contraception: hormonal and non-hormonal methods

What you'll learn

This revision guide covers the biology of contraception as required for AQA GCSE Biology. You'll understand how different contraceptive methods prevent pregnancy through hormonal or physical mechanisms, be able to compare their effectiveness, and evaluate advantages and disadvantages. This topic connects directly to your knowledge of the menstrual cycle, reproduction, and hormones.

Key terms and definitions

Contraception — methods or devices used to prevent pregnancy from occurring during or following sexual intercourse

Hormonal contraceptives — birth control methods that use synthetic hormones (oestrogen and/or progesterone) to prevent ovulation and/or fertilisation

Ovulation — the release of a mature egg from the ovary, typically occurring midway through the menstrual cycle (around day 14)

Barrier methods — contraceptive devices that physically prevent sperm from reaching the egg

Intrauterine device (IUD) — a small T-shaped device inserted into the uterus to prevent implantation of embryos

Spermicidal agents — chemical substances that kill or immobilise sperm

Abstinence — refraining from sexual intercourse, the only 100% effective method of preventing pregnancy

Sterilisation — surgical procedures that permanently prevent gametes from meeting (vasectomy in males, tubal ligation in females)

Core concepts

How hormonal contraceptives prevent pregnancy

Hormonal contraceptives contain synthetic versions of the female sex hormones oestrogen and progesterone. These work through multiple mechanisms:

Primary mechanism — inhibiting ovulation:

• High levels of oestrogen and progesterone inhibit the production of FSH (follicle-stimulating hormone) from the pituitary gland
• Without FSH, eggs do not mature in the ovaries
• No egg is released during the menstrual cycle
• Since no egg is available for fertilisation, pregnancy cannot occur

Secondary mechanisms:

• Thickening of cervical mucus, making it difficult for sperm to pass through the cervix into the uterus
• Thinning of the uterus lining (endometrium), making implantation less likely if fertilisation does occur

Types of hormonal contraception

The combined oral contraceptive pill (the pill):

• Contains both oestrogen and progesterone
• Taken daily for 21 days, followed by a 7-day break during which a withdrawal bleed occurs
• Over 99% effective when used correctly
• Must be taken at approximately the same time each day
• Effectiveness can be reduced by vomiting, diarrhoea, or certain medications (particularly antibiotics)

Advantages:

• Highly effective when used correctly
• Can reduce period pain and make periods lighter and more regular
• Reduces risk of some cancers (ovarian and endometrial)
• Rapid return to fertility after stopping

Disadvantages:

• Must remember to take it daily
• Does not protect against sexually transmitted infections (STIs)
• Can cause side effects including headaches, nausea, mood changes
• Small increased risk of blood clots, particularly in smokers over 35
• Not suitable for women with certain health conditions

Progesterone-only methods:

The mini-pill (progesterone-only pill):

• Contains only progesterone
• Taken every day without a break
• Must be taken at the same time each day (within a 3-hour window)
• Suitable for women who cannot take oestrogen

Contraceptive injection:

• Single injection of progesterone lasting 8-12 weeks
• Over 99% effective
• No daily routine required
• Fertility may take up to one year to return after stopping

Contraceptive implant:

• Small rod inserted under the skin of the upper arm
• Releases progesterone continuously for 3 years
• Over 99% effective
• Can be removed at any time with rapid return to fertility

Intrauterine system (IUS):

• T-shaped device inserted into the uterus that releases progesterone
• Lasts 3-5 years depending on type
• Over 99% effective
• Also thins the uterine lining

Non-hormonal barrier methods

Barrier methods work by preventing sperm from reaching the egg. They do not involve hormones and therefore do not affect the menstrual cycle.

Male condoms:

• Thin latex or polyurethane sheaths worn over the erect penis
• Collect semen during ejaculation, preventing sperm from entering the vagina
• Approximately 98% effective with perfect use, but typical use effectiveness is around 82%
• The only contraceptive method (besides female condoms) that provides protection against STIs including HIV, chlamydia, and gonorrhoea
• No side effects or hormonal changes
• Readily available without prescription
• Can split or slip off if used incorrectly

Female condoms:

• Polyurethane pouch inserted into the vagina before intercourse
• Lines the vagina and prevents sperm from entering the uterus
• Around 95% effective with perfect use, 79% with typical use
• Provides some STI protection
• More expensive and less widely available than male condoms

Diaphragms and cervical caps:

• Silicone cups inserted into the vagina to cover the cervix
• Must be used with spermicidal gel or cream
• Must be fitted by a healthcare professional to ensure correct size
• 92-96% effective with perfect use
• Must be left in place for at least 6 hours after intercourse
• Do not protect against STIs
• Require planning ahead and correct insertion technique

Non-hormonal intrauterine devices

Copper intrauterine device (copper IUD or copper coil):

• Small T-shaped plastic and copper device inserted into the uterus by a trained healthcare professional
• Copper ions are toxic to sperm and prevent fertilisation
• Also prevents implantation if fertilisation does occur
• Over 99% effective
• Can remain in place for 5-10 years depending on type
• No hormonal side effects
• Can be used as emergency contraception if fitted within 5 days of unprotected intercourse

Advantages:

• Highly effective long-term contraception
• No daily routine or remembering required
• Fertility returns immediately after removal
• No hormonal side effects

Disadvantages:

• Periods may become heavier, longer, or more painful
• Small risk of infection during insertion
• Small risk of expulsion or perforation of the uterus
• Does not protect against STIs
• Requires a trained professional for insertion and removal

Natural methods and permanent methods

Natural family planning (fertility awareness):

• Monitoring body temperature, cervical mucus, and cycle length to identify fertile days
• Avoiding intercourse or using barrier methods during fertile period
• Requires detailed record-keeping and regular cycles
• 76-99% effective depending on method and user diligence
• No physical side effects but requires significant commitment and training

Abstinence:

• Complete avoidance of sexual intercourse
• 100% effective at preventing pregnancy and STI transmission
• May not be practical or desirable for many people

Permanent surgical methods:

Vasectomy (male sterilisation):

• Surgical procedure where the sperm ducts (vas deferens) are cut or sealed
• Prevents sperm from being released in semen during ejaculation
• Over 99% effective
• Does not affect sexual function or testosterone production
• Should be considered permanent, although reversal is sometimes possible

Tubal ligation/occlusion (female sterilisation):

• Surgical procedure where the fallopian tubes are cut, sealed, or blocked
• Prevents eggs from travelling from ovaries to uterus and sperm from reaching eggs
• Over 99% effective
• Does not affect menstrual cycle or hormone production
• Should be considered permanent

Emergency contraception

Emergency contraception prevents pregnancy after unprotected intercourse or contraceptive failure (e.g., split condom).

Emergency contraceptive pill:

• Contains levonorgestrel (progesterone) or ulipristal acetate
• Most effective when taken as soon as possible after intercourse
• Levonorgestrel effective up to 72 hours; ulipristal up to 120 hours
• Works primarily by delaying or preventing ovulation
• 58-95% effective depending on timing and which pill is used
• Does not protect against STIs

Copper IUD as emergency contraception:

• Most effective form of emergency contraception (over 99%)
• Can be fitted up to 5 days after unprotected intercourse
• Can remain in place for ongoing contraception

Comparing contraceptive effectiveness

When evaluating contraceptive methods, consider:

Effectiveness rates:

• Typical use vs. perfect use (human error significantly reduces effectiveness of some methods)
• Methods requiring no user action (implants, IUDs) have higher typical use effectiveness
• User-dependent methods (pills, condoms) have lower typical use effectiveness

Protection against STIs:

• Only barrier methods (particularly condoms) provide STI protection
• Hormonal and intrauterine methods provide no STI protection
• Dual protection (condoms plus another method) recommended for those at STI risk

Reversibility:

• Most methods are reversible with rapid return to fertility
• Sterilisation should be considered permanent
• Contraceptive injection may delay return to fertility

Side effects and contraindications:

• Hormonal methods may cause side effects and are unsuitable for some women
• Non-hormonal methods avoid hormonal side effects but may have other disadvantages
• Individual health status affects which methods are appropriate

Worked examples

Example 1: Explain how the contraceptive pill prevents pregnancy. [4 marks]

Mark scheme answer:

• The pill contains oestrogen and progesterone [1 mark]
• These hormones inhibit the release of FSH from the pituitary gland [1 mark]
• Without FSH, eggs do not mature in the ovaries [1 mark]
• No egg is released/no ovulation occurs, so fertilisation cannot take place [1 mark]

Examiner note: Alternative correct answers include thickening cervical mucus or thinning the uterus lining, but these are secondary mechanisms. Focus on the primary mechanism of preventing ovulation for full marks.

Example 2: A couple are deciding between using condoms or the contraceptive implant. Evaluate these two methods. [6 marks]

Mark scheme answer:

Effectiveness:

• The implant is over 99% effective, more effective than condoms [1 mark]
• Condoms are only about 82% effective with typical use because they can be used incorrectly/split [1 mark]

STI protection:

• Condoms protect against sexually transmitted infections, the implant does not [1 mark]
• This makes condoms better for new relationships or people with multiple partners [1 mark]

Convenience/other factors:

• The implant requires no action during intercourse/lasts for 3 years [1 mark]
• Condoms must be used correctly each time, which requires planning/interrupting sex [1 mark]

Examiner note: For "evaluate" questions, you must present both advantages and disadvantages or compare both options. Six marks requires detailed, balanced analysis across multiple criteria.

Example 3: Describe how a copper IUD prevents pregnancy. [3 marks]

Mark scheme answer:

• The copper IUD is inserted into the uterus [1 mark]
• Copper ions are released which are toxic to sperm/prevent fertilisation [1 mark]
• It also prevents implantation of any embryo in the uterus lining [1 mark]

Examiner note: Don't confuse the copper IUD (non-hormonal) with the IUS (releases progesterone). The question specifically asks about copper IUD, so describing hormonal mechanisms would score zero marks.

Common mistakes and how to avoid them

• Confusing the copper IUD with the IUS. The copper IUD is non-hormonal and works through copper ions; the IUS releases progesterone. Read the question carefully to identify which device is being asked about.

• Stating that hormonal contraceptives "stop periods" or "stop the menstrual cycle." They prevent ovulation (egg release) but most methods still involve cyclical changes and bleeding. Use precise language: "prevents ovulation" not "stops periods."

• Forgetting that only barrier methods protect against STIs. A common exam trap is asking you to recommend contraception for someone who needs STI protection—always mention condoms in this context, even if other methods are more effective at preventing pregnancy.

• Claiming the contraceptive pill is 100% effective. No method except abstinence is 100% effective. The pill is over 99% effective with perfect use, but typical use effectiveness is lower (around 91%) due to human error such as missed pills.

• Describing how condoms work without mentioning the prevention of sperm reaching the egg. Don't just say "it's a barrier"—explain that it prevents sperm from entering the vagina/reaching the egg to fertilise it.

• Confusing FSH and LH or other hormones. The pill works by inhibiting FSH specifically. Make sure you can distinguish between FSH (stimulates egg maturation), LH (triggers ovulation), oestrogen, and progesterone in your answers.

Exam technique for "Contraception: hormonal and non-hormonal methods"

• "Describe" vs "Explain" command words: "Describe" requires you to state what happens (e.g., "the pill prevents ovulation"). "Explain" requires you to state why/how it happens (e.g., "the pill contains oestrogen which inhibits FSH release, so eggs do not mature"). Always check the command word.

• Watch the mark allocation. For 1-2 marks, one or two clear points are sufficient. For 4-6 marks, you need multiple detailed points or comparisons. If a question is worth 6 marks and asks you to "evaluate," you must present a balanced argument with advantages and disadvantages.

• Use correct terminology. Say "prevents ovulation" not "stops eggs," "sperm" not "seeds," "uterus" not "womb" (though womb is acceptable). Scientific terminology demonstrates understanding and prevents ambiguity.

• Link structure to function. When describing barrier methods, explain the physical mechanism (e.g., "the condom prevents sperm from entering the vagina"). When describing hormonal methods, explain the hormonal mechanism (e.g., "oestrogen inhibits FSH release").

Quick revision summary

Contraception prevents pregnancy through hormonal or physical mechanisms. Hormonal methods (pill, implant, injection, IUS) primarily work by preventing ovulation through inhibiting FSH release; they're highly effective but don't protect against STIs. Non-hormonal barrier methods (condoms, diaphragms) physically prevent sperm reaching the egg and condoms protect against STIs. The copper IUD releases toxic copper ions and prevents implantation. Permanent methods include vasectomy and tubal ligation. Effectiveness varies with perfect vs typical use. Choice depends on effectiveness, reversibility, STI protection needs, and side effects.