Contraception (OCR Gateway GCSE Biology: Combined Science)

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Hormonal Contraception

Oral contraceptives

  • Contain hormones to inhibit FSH production so that no eggs mature; there are two types:
    • The combined pill
      • contains oestrogen and progesterone which is over 99% effective at preventing pregnancy
      • High levels of oestrogen inhibit FSH production preventing the maturation and release of eggs
      • Progesterone also plays a role in inhibiting the release of mature eggs and stimulates the production of a thick mucus which prevents sperm from reaching any eggs that are released
    • The mini-pill
      • A progesterone-only pill, which has fewer side effects

Injection, implant or skin patch

  • Slowly release progesterone to inhibit the maturation and release of eggs for a number of months or years
    • Benefits of implants reduce the chance of someone forgetting to take the pill (which should be taken at the same time every day to be most effective)

Intrauterine devices (IUD)

  • Inserted into the uterus to prevent the implantation of an embryo or release a hormone 
    • A plastic IUD
      • Produces progesterone which stimulates the production of a thick mucus lining preventing sperm from reaching any eggs

Non-Hormonal Contraception

Barrier methods

  • These all work by preventing sperm from reaching the egg
  • Condom
    • Latex sheath worn over the penis
    • Prevents sperm entering the vagina as ejaculate remains in condom
    • Protects against STIs
  • Femidom
    • Latex sheath inserted into the vagina
    • Prevents entry of sperm into the vagina
  • Diaphragm
    • A rubber cap that fits over the entrance to the cervix
    • Prevents entry of sperm into uterus
    • Often used with a spermicide (cream which kills sperm)

Natural methods

  • Abstinence
    • Avoiding sexual intercourse completely
    • Complete abstinence is the only 100% effective method at preventing pregnancy
  • Natural family planning
    • Avoiding sexual intercourse during the fertile period of the menstrual cycle when ovulation occurs
    • This method requires an understanding of the fertility signals such as
      • Length of menstrual cycle
      • Body temperature changes throughout the cycle
      • Changes in cervical secretions throughout the cycle

Surgical methods

  • Vasectomy
    • The sperm ducts are cut, meaning that no sperm is present in the semen when ejaculation occurs
    • Very effective but difficult to reverse
  • Female sterilisation (tubal ligation)
    • The oviducts are cut or tied off, preventing eggs from reaching the uterus or sperm from reaching the eggs
    • Very effective but difficult to reverse

Evaluating Methods of Contraception

Types of birth controlThere are many different forms of contraception, each with associated benefits and risk

  • Each method of contraception comes with its own risks and benefits
  • Some of the considerations might be:
    • Reliability
      • Success rates vary for the different types with the most effective forms of contraception being  
    • Side-effects
      • Many of the hormonal methods can have side-effects which include headaches, irregular, painful or heavy periods, acne, changes to mood or energy levels, weight gain
    • Human error
      • If a method of contraception is incorrectly implemented it may not work for example, if a condom is damaged, used wrongly or if it splits
      • Whilst natural family planning methods do not have associated side effects, there are risks of failure if due to stress, illness or other lifestyle changes which may affect the menstrual cycle
    • Invasive nature of insertion
      • Some methods require procedures which must be carried out by medical professionals which can be invasive and intimidating, or sometimes painful
    • Frequency of application
      • Some methods are required before each period of sexual intercourse (condoms for example) whereas others are long lasting and remain effective for months or years.
      • This, however, can also have its drawbacks as it is down to the individual to remember to replace the form of contraception at the right time
    • Sexually transmitted diseases
      • Only condoms provide a barrier to STI's, all other methods still expose the individual to the risks

Different Methods of Contraception Table


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