11.7 The Artificial Control of Fertility

A free GCSE Biology lesson for AQA (8461) from OBA School: hormonal and non-hormonal methods of contraception and how to evaluate them. Watch the video, read the explanation and worked examples, then try the revision questions. You can work through the full lesson, with every video, practice quizzes and printable worksheets with mark schemes, in our free online course.

What you will learn

• Explain how hormonal contraceptives prevent pregnancy
• Describe non-hormonal methods: barrier methods, IUDs, spermicides, abstinence and sterilisation
• Use data to compare how effective different methods are
• Evaluate hormonal and non-hormonal methods of contraception

Key words

• Contraception: Any method used to prevent pregnancy.
• Oral contraceptive: A pill containing hormones that stops eggs maturing, so no egg is released.
• Barrier method: A physical barrier, such as a condom or diaphragm, that stops sperm reaching an egg.
• IUD: Intrauterine device: a small device placed in the uterus that prevents implantation of an embryo or releases hormones.
• Spermicide: A chemical that kills or disables sperm.
• Sterilisation: Surgery that permanently stops eggs or sperm reaching each other (e.g. a vasectomy).

How contraception works

To prevent pregnancy, a method must do at least one of these: stop eggs maturing or being released, stop sperm reaching an egg, or stop an embryo implanting in the uterus. Knowing the hormones of the menstrual cycle explains how hormonal methods work.

Key fact: Hormonal methods use oestrogen and/or progesterone to inhibit FSH, so no eggs mature. Non-hormonal methods work in other ways.

Hormonal methods

• Oral contraceptive (“the pill”); How it works Contains hormones that inhibit FSH production, so no eggs mature; Notes Must be taken every day; very effective if used correctly
• Implant, injection or skin patch; How it works Slow release of progesterone, which inhibits the maturation and release of eggs; Notes Implant lasts about 3 years; injection about 3 months
• Hormonal IUD; How it works Releases progesterone in the uterus; Notes Lasts several years

Advantages: very effective; nothing to do at the time of sex. Disadvantages: possible side effects (such as headaches, mood changes or irregular bleeding); no protection against sexually transmitted infections (STIs); some must be fitted by a doctor or nurse.

Non-hormonal methods

• Condom (male or female); How it works Barrier: traps sperm so they cannot reach the egg. Also protects against STIs.
• Diaphragm; How it works Barrier: a dome placed over the cervix; usually used with spermicide.
• Spermicidal agents; How it works Chemicals that kill or disable sperm; not very effective on their own.
• Copper IUD; How it works Fitted in the uterus; prevents the implantation of an embryo.
• Abstaining; How it works Not having intercourse at the time an egg may be in the oviduct.
• Surgical sterilisation; How it works Cutting or blocking the sperm ducts (vasectomy) or oviducts. Usually permanent.

Worked example: exam tip

“Suggest why a couple might choose condoms.” (2 marks)
They have no hormonal side effects (1) and they also protect against sexually transmitted infections (1).

Answer: link the reason to the method

Using data to evaluate methods

How well a method works depends on how carefully it is used. The chart shows approximate typical-use figures.

Worked example: using the percentages

500 women use the combined pill for a year. Estimate how many become pregnant.
7% of 500 = 0.07 × 500 = 35
How many times more likely is a pregnancy with a male condom than with an implant? 13 ÷ 0.1 = 130

Answer: about 35 women; 130 times

Exam tip: Methods that do not depend on the user remembering (implants, IUDs) have the lowest failure rates.

Common mistakes

• Saying the pill “kills sperm” or “kills the egg”. It stops eggs maturing by inhibiting FSH.
• Saying all methods protect against STIs. Only condoms do.
• Saying a copper IUD releases hormones. A copper IUD prevents implantation; only hormonal IUDs release progesterone.
• Giving only advantages in an “evaluate” question. Give both sides and a conclusion.

Revision questions

Try these, then check your answers below each one.

Question 1. How does the combined oral contraceptive pill prevent pregnancy? (Choose from: Its hormones inhibit FSH, so no eggs mature, It kills sperm in the vagina, It blocks the oviducts, It makes the uterus lining thicker.)

Answer: Its hormones inhibit FSH, so no eggs mature

Working: The hormones in the pill inhibit FSH production, so no eggs mature and none are released.

Question 2. True or false? Condoms protect against sexually transmitted infections as well as preventing pregnancy.

Answer: True

Working: True. Condoms are the only method listed in this section that also protect against STIs.

Question 3. Which is a surgical method of contraception? (Choose from: Vasectomy, Diaphragm, Skin patch, Spermicidal gel.)

Answer: Vasectomy

Working: A vasectomy cuts and seals the sperm ducts; it is usually permanent.

Related lessons

• Previous lesson: 11.6 Hormones and the Menstrual Cycle
• Next lesson: 11.8 Infertility Treatments
• In this chapter: 11.1 Principles of Hormonal Control
• In this chapter: 11.2 The Control of Blood Glucose Levels
• In this chapter: 11.3 Treating Diabetes

Continue in the full course

This lesson is section 11.7 (AGCBH1107) of our free GCSE Biology course for AQA. In the full course you get every video for this section, a self-marking practice quiz, a printable worksheet with a mark scheme, chapter tests, and your progress saved. Go to the full GCSE Biology course.