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The biology of controlling fertilityChemical and hormonal methods of contraception

Fertility is the ability to produce offspring. Fertility is continuous in males and cyclical in females. Infertility can have a number of causes and there are a range of infertility treatments that work in different ways. Physical and chemical methods of contraception can prevent fertilisation and pregnancy.

Part of Human BiologyPhysiology and Health

Chemical and hormonal methods of contraception

Oral contraceptives

Contraceptive pill packaging from the back showing the encased pills
Image caption,
Contraceptive pills

Human is controlled by , so fertility can be controlled using hormonal forms of contraception.

The oral contraceptive, which is known as the pill, contains or or a combination of both hormones. These hormones inhibit the production of , and eggs cannot mature.

Oestrogen at low levels stimulates the release of eggs. However at high doses, oestrogen will inhibit FSH production. After taking the pill for a while, egg development and release will stop completely. If there is no egg available, there can be no baby. This is why contraceptive pills are so effective.

There are different types of contraceptive pill:

  • Oral contraceptive pill – contains a mixture of oestrogen and progesterone that mimics the natural negative feedback effect which prevents the release of FSH and .
  • Mini-pill – contains progesterone only and causes thickening of cervical mucus
  • Morning after pill – contains a stronger dose of oestrogen and progesterone than the contraceptive pill. It prevents or delays ovulation.

Benefits and risks

MethodBenefitRisk
Oral contraceptivesMore than 99% effective if taken correctly and can reduce the risk of certain cancersPotential side effects such as changes in weight, mood, and blood pressure due to high levels of oestrogen
Contraceptive injectionsMore than 99% effectiveRepeat injections needed every 8-13 weeks before it expires or becomes ineffective
MethodOral contraceptives
BenefitMore than 99% effective if taken correctly and can reduce the risk of certain cancers
RiskPotential side effects such as changes in weight, mood, and blood pressure due to high levels of oestrogen
MethodContraceptive injections
BenefitMore than 99% effective
RiskRepeat injections needed every 8-13 weeks before it expires or becomes ineffective