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ZIMSEC O Level Combined Science Notes:Contraception: The pill

  • Are also known as birth control pills (BCPs) or
  • Oral Contraceptive Pills (OCPs)

How it works

  • They contain the two female hormones: oestrogen and progesterone
  • They prevent the release of ova/female sex cells
  • They cause growth of an unstable thin uterus lining
  • Thicken cervical mucus and disturb the movement of sperm into the uterus


  • 99.6-99.8%


  • It’s effective
  • Easy to use
  • Reversible
  • Does not interfere with sexual activity
  • Menstrual bleeding is lighter, shorter, regular and there are fewer cramps


  • Must be taken daily
  • Requires a doctor’s prescription
  • Suppresses production of breast milk
  • There is a possibility of blood clots forming and
  • A slight increase in risk of heart attack and strokes for those above 35 years old
  • There can be unpleasant side effects

Side effects

  • Slight weight change
  • Nausea
  • Breast tenderness
  • Spotting in mid cycle (drops of blood appear)
  • Mood changes
  • Loss of sexual desire

To access more topics go to the Combined Science Notes page