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5.3.5 Contraception

5.3.5 Contraception

Fertility Can Be Controlled

Definition

Contraception

The use of hormonal or non-hormonal methods to prevent pregnancy, by stopping an egg maturing, stopping sperm reaching an egg, or stopping an embryo implanting.

  1. Contraception is used to prevent pregnancy, and the methods are either hormonal or non-hormonal.
  2. Different methods have different advantages and disadvantages, so people weigh them up before choosing.
Key Idea

Contraception works in one of three ways: stopping an egg maturing, stopping sperm meeting the egg, or stopping an embryo implanting.

Hormonal Methods Stop Eggs Maturing

Definition

FSH (follicle-stimulating hormone)

A hormone from the pituitary gland that causes an egg to mature in the ovary and stimulates the ovaries to produce oestrogen.

  1. Oral contraceptives (the pill)
    1. Contain oestrogen and/or progesterone, which inhibit FSH so that no eggs mature.
    2. The combined pill contains oestrogen and progesterone, while the progesterone-only pill has fewer side effects.
  2. Injection, implant or skin patch
    1. Release progesterone slowly to stop eggs maturing and being released for months or years.
  3. Hormonal intrauterine device (IUD)
    1. Sits in the uterus and releases progesterone, which also thickens the mucus in the cervix to block sperm.
Note

The pill must be taken regularly, because if the hormone level drops the body's own hormones can take over and an egg may be released.

Non-Hormonal Methods Keep Sperm and Egg Apart

  1. Barrier methods
    1. Condoms and diaphragms stop sperm reaching the egg, and condoms also protect against sexually transmitted infections.
  2. Spermicides
    1. Chemicals that kill or disable sperm, but they are not very effective on their own.
  3. Copper intrauterine device (IUD)
    1. Releases copper ions that disable sperm and prevent an embryo implanting.
  4. Abstinence
    1. Avoiding intercourse when an egg may be in the oviduct.
  5. Surgical sterilisation
    1. Cutting or tying the sperm ducts in men (a vasectomy) or the oviducts in women.
Note

Barrier methods work better when combined with a spermicide.

Evaluating Contraception

  1. Hormonal methods are very effective, but the pill can cause side effects and must be remembered every day.
  2. Implants and IUDs last for years and remove the risk of forgetting.
  3. Barrier methods have no hormone side effects and condoms protect against infections, but they can slip or tear.
  4. Spermicides and natural methods are the least reliable, while surgical sterilisation is the most reliable but is permanent and hard to reverse.
Common Mistake

Which method a person chooses also depends on personal, religious and ethical views, so questions about contraception cannot be answered by science alone.

Choosing a Method

  1. Hormonal methods stop eggs maturing or being released.
  2. Barrier methods and spermicides stop sperm reaching the egg.
  3. IUDs, sterilisation and abstinence prevent fertilisation or implantation in other ways.
  4. The best choice balances effectiveness, side effects, protection from infection and personal beliefs.
Self review
  • Give two hormonal and two non-hormonal methods of contraception.
  • How do oral contraceptives stop eggs maturing?
  • Which method also protects against sexually transmitted infections?
  • Which methods are the most and least reliable?
  • Why can questions about contraception not be answered by science alone?
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Contraception is the use of hormonal or non-hormonal methods to prevent pregnancy. It can work through one or more mechanisms, including stopping an egg maturing, stopping sperm reaching or fertilising an egg, or preventing implantation of an embryo. Methods that stop sperm and egg from meeting include condoms, spermicide, and sterilisation: vasectomy blocks the sperm ducts, while female sterilisation blocks the oviducts. The copper IUD primarily prevents fertilisation by releasing copper ions that impair sperm movement and function.

Hormonal methods change hormone levels in the body. Non-hormonal methods physically block sperm, disable sperm, or permanently prevent sperm and egg from meeting. Different methods have different effectiveness, side effects, durations, infection protection, and effects on personal or religious beliefs.

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What are the three ways contraception can prevent pregnancy?

5.3.5 Contraception Revision Guide

  1. GCSE
  2. /Biology
  3. /5.3.5 Contraception

Revision notes for AQA GCSE Biology 5.3.5 Contraception. Open the guide for explanations and worked examples. Written against the AQA GCSE Biology (8461) specification, so the content matches what's examinable rather than general Biology background.