Contraception (AQA GCSE Combined Science: Trilogy: Biology): Revision Note

Control of fertility

• Fertility can be controlled by a variety of hormonal and non-hormonal methods

• Contraceptive methods aim to prevent fertilisation and pregnancy, and include:

  • the use of hormones (oestrogen and progesterone)

  • non-hormonal methods (such as the use of barriers or surgery)

• Benefits of contraception include:

  • preventing unwanted pregnancies

  • preventing pregnancies that may lead to risks to the mother’s health

  • some methods also give protection from sexually transmitted infections

• The counter-arguments involve ethical and religious concerns about making decisions that may or may not lead to life

• Hormones can also be used to increase the chance of pregnancy occurring when it previously might not have done

Types of contraception

• Humans can use barrier, chemical, surgical and natural contraceptive methods to prevent pregnancy

Chemical

• Oral contraceptives contain hormones to inhibit FSH production so that no eggs mature:

  • E.g. a pill that contains oestrogen will inhibit FSH production

• Injection, implant or skin patch release progesterone to inhibit the maturation and release of eggs for a number of months or years

• Intrauterine devices (IUDs) prevent the implantation of an embryo, or release a hormone

• Spermicidal agents kill or disable sperm; this is used in combination with other methods

Barrier

• Barrier methods such as condoms and diaphragms prevent the sperm from reaching an egg

  • Male and female condoms are the only barrier method that can prevent the spread of sexually transmitted infections

Natural

• Abstinence may involve:

  • avoiding sexual intercourse entirely

  • refraining from intercourse at times of the menstrual cycle when an egg may be in the oviduct

• Natural methods are less reliable than other methods of contraception

Surgical

• Surgical methods of male and female sterilisation

  • E.g. the sperm ducts (the tube connecting the testes to the penis) can be cut and tied in a procedure called a vasectomy

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