Contraception: barrier methods such as condoms and diaphragms which prevent the sperm reaching an egg

The idea

Barrier contraception works physically: it places a latex or silicone barrier between the penis and the vagina, or across the cervix, so that sperm cannot swim to meet the egg. A condom is rolled onto the erect penis and also reduces the transmission of sexually transmitted infections because it stops fluids mixing. A diaphragm is a shallow dome inserted into the vagina before intercourse to cover the cervix, usually with spermicide. Both are non-hormonal, so they do not alter the menstrual cycle, and they act only during that act of intercourse. Their effectiveness depends on correct and consistent use: a torn condom or a diaphragm left in place for too short a time allows sperm through. This is why barrier methods are described as preventing fertilisation rather than preventing implantation.

What earns the marks

• State that barrier methods are physical, non-hormonal methods that stop sperm and egg meeting.
• Name condoms and diaphragms as examples and describe where each is placed.
• Explain that a condom covers the penis and a diaphragm covers the cervix, so sperm cannot reach the egg.
• Link correct use to effectiveness, for example a split condom or a diaphragm inserted too late allows sperm through.
• Recognise that condoms also reduce the spread of sexually transmitted infections, whereas diaphragms do not.
• Compare barrier methods with hormonal methods, noting that barriers do not change the menstrual cycle.

Common mistakes and how to put them right

• Saying barrier methods kill sperm.

  Put it right: They physically block sperm, although a diaphragm may be used with a spermicide that does kill sperm.

• Confusing a diaphragm with a contraceptive pill.

  Put it right: A diaphragm is a physical barrier placed over the cervix, while the pill is hormonal and taken daily.

• Claiming barrier methods prevent implantation.

  Put it right: They prevent fertilisation by stopping sperm reaching the egg, so no embryo forms.

Exam tips

• Use the phrase 'prevents the sperm reaching the egg' when explaining how a barrier method works.
• Give one named example and its position, such as 'a diaphragm covers the cervix', to show precise knowledge.
• If asked to evaluate, mention that barrier methods do not affect hormones and that condoms also reduce STI transmission.