Contraception (AQA GCSE Biology: Combined Science)

• 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) as well as non-hormonal methods (such as the use of barriers or surgery)
• Hormones can also be used to increase the chance of pregnancy occurring when it previously might not have done
• Explain everyday and technological applications of science; evaluate associated personal, social, economic and environmental implications; and make decisions based on the evaluation of evidence and arguments

There are many different types of contraception but not everyone may have access to them

• Contraceptive methods are important in keeping family sizes small and in limiting the increase in human population
• Humans can use barrier, chemical, surgical and natural contraceptive methods to prevent a pregnancy
• Some birth control methods also give protection from sexually transmitted infections

Chemical

• Oral contraceptives that 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
  • There is also the progesterone-only pill which has fewer side effects

• Injection, implant or skin patch of slow-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) which prevent the implantation of an embryo or release a hormone; there are two types
  • A plastic IUD produces progesterone which stimulates the production of a thick mucus lining preventing sperm from reaching any eggs
  • A copper IUD works by releasing low levels of copper ions which disable sperm cells

Barrier

• Barrier methods such as condoms and diaphragms prevent the sperm from reaching an egg
  • Condoms are the only barrier method that can prevent the spread of sexually transmitted infections

• Spermicidal agents which kill or disable sperm – these are only 70 - 80% effective

Natural

• Abstaining from intercourse when an egg may be in the oviduct
  • Complete abstinence is the only 100% effective method at preventing pregnancy
  • Natural methods involve avoiding intercourse during the most fertile part of the menstrual cycle but they are not highly effective as fertility cannot be accurately predicted

Surgical

• Surgical methods of male and female sterilisation
  • In a female, the oviducts which connect the ovaries to the uterus (also called the fallopian tubes) can be cut and tied
  • In a male, the sperm ducts (the tube connecting the testes to the penis) can also be cut and tied in a procedure called a vasectomy
  • Both methods are highly effective but there have been a small number of cases where tubes have rejoined