A level Biology exam revision resources written by A level Examiners


There are many different causes of infertility in couples. There is a roughly equal split in these between factors which affect the male, and factors which affect the female. Some of the most common causes of infertility are:

  • Low sperm count.
  • Damage to Fallopian tubes.
  • Failure to ovulate.

There are two main treatments that are considered at A level. These are the use of hormones and drugs and in vitro fertilisation.

If a woman does not ovulate naturally, she may be treated with injections of FSH. The hormone is administered to the female in order promote ovulation. Another treatment can be to inject a drug called Clomiphene Citrate. Clomiphene blocks the normal negative feedback effect of oestrogen on FSH production. This boosts the concentration of FSH present and thus promotes ovulation.

The sequence of events that take place in a cycle of in vitro fertilisation is as follows:

  • The woman is treated with hormone to cause superovulation. This means several eggs can be removed in a single cycle.
  • A sample of sperm is taken from the male.
  • The eggs are fertilised in vitro. If the sperm are of very low quality, one may be injected directly into an egg using a micropipette.
  • A number of embryos are implanted into the female (2-3 in the UK).
  • If the woman does not begin her usual menstrual cycle a pregnancy test can be used to confirm the pregnancy.

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