Controlling Fertility

• Pregnancy


  Can happen if sperm reaches the ovulated egg
• Contraception


  Tries to stop sperm reaching the egg
• Hormones used to reduce fertility

  1. Oestrogen prevents release of egg

  2. Oestrogen inhibits FSH production, stopping egg development

  3. Progesterone stimulates thick mucus, preventing sperm reaching egg
• Combined oral contraceptive pill

  Oral contraceptive containing oestrogen and progesterone
• Combined oral contraceptive pill

  • Over 99% effective at preventing pregnancy
  • Can cause side effects like headaches and nausea
  • Doesn't protect against sexually transmitted diseases
• Progesterone-only pill


  Has fewer side effects than combined pill, just as effective
• Other contraceptives containing hormones

  • Contraceptive patch
  • Contraceptive implant
  • Contraceptive injection
  • Intrauterine device (IUD)
• Contraceptive patch


  • Contains oestrogen and progesterone, lasts one week
• Contraceptive implant


  • Releases continuous progesterone, stops ovulation, makes it hard for sperm to reach egg, prevents implantation, lasts 3 years
• Contraceptive injection


  • Contains progesterone, lasts 2-3 months
• Intrauterine device (IUD)


  • Plastic IUDs release progesterone, copper IUDs prevent sperm survival
• Barriers


  Stop egg and sperm meeting
• Barrier contraceptives


  • Condoms
  • Diaphragm
• Spermicide


  Substance that disables or kills sperm
• Sterilisation


  Cutting or tying fallopian tubes (female) or sperm duct (male), permanent procedure
• Natural methods


  Avoiding sexual intercourse on fertile days of menstrual cycle
• Abstinence


  Not having sexual intercourse
• Hormones used to increase fertility

  FSH and LH can be given as fertility drugs to stimulate ovulation
• Using hormones to increase fertility

  • Helps many women get pregnant who previously couldn't
  • Doesn't always work, may require multiple attempts
  • Can result in unexpected multiple pregnancies
• IVF


  1. Collect eggs from woman's ovaries

  2. Fertilise eggs in lab using man's sperm

  3. Grow fertilised eggs into embryos

  4. Transfer one or two embryos to woman's uterus
• IVF


  • Can give infertile couple a child
  • Multiple births are risky for mother and babies
  • Average success rate in UK is about 26%
  • Physically and emotionally stressful for woman
• Advances in IVF


  • Improved microscope techniques
  • Specialised micro-tools for eggs and sperm
  • Time-lapse imaging to monitor embryo growth
• Some people think IVF is unethical because it results in unused embryos that are destroyed
• Some people think genetic testing of embryos before implantation raises ethical issues as it could lead to selection of preferred characteristics