Intrauterine contraception

Intrauterine contraception uses a small device placed in the uterus to prevent pregnancy. There are two types: a non-hormonal copper device and a hormonal device.

Copper and hormonal devices

A copper device interferes with sperm, primarily preventing them from fertilising an egg. It may also prevent a fertilised egg from implanting in the uterine lining.

A hormonal intrauterine device releases a hormone called a progestogen. This thickens the mucus at the cervix, the opening to the uterus, making it harder for sperm to pass through and reach an egg. The hormone also thins the uterine lining.

Use of intrauterine contraception

An intrauterine device provides long-lasting contraception without requiring action during each act of intercourse. It must be fitted and removed by a trained health professional.

Neither type protects against sexually transmitted infections.

Hormonal contraception

Hormonal contraceptives use hormones to reduce the chance of pregnancy. They can prevent an egg from maturing or being released from an ovary. The release of an egg is called ovulation.

Some oral contraceptive pills contain hormones that inhibit the production of follicle-stimulating hormone (FSH). FSH normally stimulates eggs to mature in the ovaries. When its production is inhibited, eggs do not mature.

Injections, implants and skin patches also deliver hormones, including progestogens. These hormones can inhibit egg maturation and ovulation.

Hormonal contraception: Use and duration

The methods differ in how they are used and how long they act:

• Pills must be taken regularly.
• Injections are renewed at intervals.
• Implants can act for years.
• Skin patches are replaced regularly.

Effectiveness depends partly on using the method correctly and renewing or replacing it on time. Hormonal contraceptives do not protect against sexually transmitted infections.

Fertility-awareness contraception

Fertility-awareness contraception can involve avoiding vaginal intercourse on days when sperm could meet an egg. These days are called the fertile window.

The fertile window includes the time around ovulation, when an egg is released from an ovary and may be in an oviduct. It also includes days before ovulation because sperm can survive in the reproductive tract for several days. Sperm from intercourse before ovulation may therefore still be present when the egg is released.

Fertility awareness: effectiveness and protection

This approach does not require hormones or a device. Its effectiveness depends on identifying fertile days accurately and avoiding vaginal intercourse during them. Ovulation does not always occur at the same time, so predicting the fertile window is uncertain.

Fertility-awareness contraception does not protect against sexually transmitted infections during intercourse.

Barrier contraception

Barrier methods of contraception physically prevent sperm from reaching an egg. If sperm cannot reach the egg, fertilisation cannot occur.

A condom forms a barrier that collects semen, the fluid containing sperm. A diaphragm covers the cervix, the opening to the uterus, preventing sperm from entering the uterus. A diaphragm can be used with spermicide, a substance that kills sperm.

Barrier methods must be used correctly during intercourse. If a barrier is damaged or used incorrectly, sperm may pass through and reach an egg.

Condoms also reduce the risk of sexually transmitted infections (STIs) by acting as a barrier during sexual contact. Diaphragms do not provide the same protection against STIs.

Spermicidal contraception

Spermicides are chemicals placed in the vagina to kill or disable sperm. This reduces the chance that sperm will reach and fertilise an egg, making pregnancy less likely.

Spermicide can be used alone or with a barrier method, such as a diaphragm. The diaphragm blocks sperm from reaching the egg, while the spermicide acts on the sperm.

Spermicides must be used correctly to be effective. When used alone, they are generally less effective at preventing pregnancy than many other contraceptive methods. They do not protect against sexually transmitted infections and can cause irritation.

Surgical sterilisation

Surgical sterilisation is a long-term method of contraception intended to be permanent. It prevents sperm and an egg from meeting by cutting, sealing or blocking the tubes through which they travel.

Vasectomy

In a vasectomy, the tubes that carry sperm from the testes are cut or sealed. This stops sperm from entering the semen, so the semen cannot fertilise an egg once the procedure has worked.

Sperm can remain in the tubes for a time after the operation. Another method of contraception is therefore needed until a semen test confirms that the procedure has worked.

Female sterilisation

In female sterilisation, the oviducts—the tubes that carry eggs—are cut, sealed or blocked. This prevents sperm from reaching an egg.

Both procedures are highly effective, but reversal may not be possible. Sterilisation does not protect against sexually transmitted infections.

Evaluating contraceptive methods

Choosing a contraceptive method means weighing how well it prevents pregnancy against its practical and personal advantages and limitations. A method that suits one person may not suit another.

Effectiveness in everyday use

A method’s effectiveness with typical use may be lower than its effectiveness when used correctly every time. In everyday life, a person may forget to use a method, use it incorrectly or use it at the wrong time.

Long-acting implants and intrauterine devices do not require action at each act of intercourse. By contrast, barrier methods depend on consistent, correct use, while fertility-awareness methods depend on identifying and responding to fertile times. These differences matter when considering how reliably a method can be used in a person’s circumstances.

Other factors in choosing contraception

Methods differ in duration and reversibility. Some provide contraception for a long time but can be stopped or removed; sterilisation is intended to be permanent. Methods may also differ in possible side effects, risks associated with a procedure, and convenience.

Condoms have an additional benefit: they reduce the risk of sexually transmitted infections as well as pregnancy. The most suitable choice depends on which benefits and limitations matter most to the individual.