Contraception: spermicidal agents which kill or disable sperm

The idea

Spermicidal agents are chemical contraceptives that kill sperm or reduce their motility so they cannot reach and fertilise the egg. They are placed in the vagina before intercourse, usually as a cream, gel, foam, pessary or on a condom, and they work locally in the reproductive tract rather than changing the woman's hormones. Because sperm must swim through the cervix and uterus to meet the egg in the oviduct, immobilising or destroying sperm in the vagina prevents fertilisation. Spermicides are often combined with a barrier method such as a condom or diaphragm to improve effectiveness, since used alone they are less reliable. They do not protect against sexually transmitted infections, so a condom is still needed for that purpose.

What earns the marks

• Spermicidal agents are chemical contraceptives placed in the vagina before intercourse.
• Immobilised or destroyed sperm cannot swim through the cervix and uterus to reach the egg in the oviduct.

Common mistakes and how to put them right

• Thinking spermicides are hormones.

  Put it right by stating they are chemicals that act directly on sperm in the vagina and do not change the menstrual cycle.

• Assuming spermicides alone are highly effective.

  Put it right by explaining they are usually combined with a barrier method because used alone they are less reliable.

• Believing spermicides protect against sexually transmitted infections.

  Put it right by stating they do not, and a condom is needed.

Exam tips

• Link the method to the biological reason it works: sperm are killed or disabled, so fertilisation cannot occur.
• Use precise terms such as sperm, oviduct, fertilisation and motility rather than vague words like 'germs' or 'blocking'.
• When comparing contraception methods, state that spermicides are non-hormonal and often used with a barrier method.