💊 Oral contraceptives
Oral contraceptives, or "the pill", are tablets that contain hormones. The hormones inhibit FSH production, so no eggs mature in the ovaries. With no mature egg, there is nothing for sperm to fertilise.
Hormonal Coordination in Humans » Contraception
What you'll learn this session
Study time: 30 minutes
AQA spec: 4.5.3.5
- The hormonal methods of contraception and how they work
- The non-hormonal methods: barrier, intrauterine, spermicidal, abstaining and sterilisation
- How to evaluate the different methods
- Why issues around contraception cannot be answered by science alone
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Unlock This CourseControlling fertility
Fertility can be controlled. Many people use contraception to decide when, or whether, to have a baby. Contraception works in several ways: it stops an egg being matured or released, it stops sperm reaching an egg, it kills or disables sperm, or it stops an embryo settling into the uterus.
The methods split into two groups: hormonal methods, which use hormones to stop eggs maturing or being released, and non-hormonal methods, which work in other ways. An intrauterine device is listed with the non-hormonal methods, but some release a hormone.
Key terms:
- Contraception: a method used to prevent pregnancy.
- Hormonal contraception: a method that uses hormones to stop eggs maturing or being released.
- Barrier method: a method that stops sperm reaching an egg.
- Sterilisation: a surgical method that usually permanently stops a person being able to have children.
Hormonal methods
Hormonal methods use hormones so that an egg is not matured or released.
💉 Injection, implant or patch
These release progesterone slowly into the body. The progesterone inhibits the maturation and release of eggs. One injection or implant can work for a number of months or years. A skin patch is stuck on the skin and releases the hormone slowly.
Hormonal methods are very effective when used correctly. The pill must be taken regularly, so a forgotten tablet can make it less reliable. Implants and injections do not need daily action, which is a big advantage.
Hormonal methods can also have side effects in some people, and they do not protect against sexually transmitted diseases.
Common mistakes
Do not say the pill "kills eggs" or "kills sperm". The pill contains hormones that stop eggs from maturing because FSH production is inhibited. Hormonal methods work on eggs. They are not barrier methods.
Non-hormonal methods
🛡 Barrier methods
Condoms and diaphragms prevent the sperm reaching an egg. A condom covers the penis. A diaphragm is a soft dome that sits over the opening of the uterus.
⚙ Intrauterine devices
An intrauterine device (IUD) is a small device fitted inside the uterus. It either prevents the implantation of an embryo or it releases a hormone. It can stay in place for a long time.
⚠ Spermicidal agents
Spermicides are chemicals that kill or disable sperm. They are often used together with a barrier method.
Two more non-hormonal methods do not use any device or chemical at all.
- Abstaining from intercourse when an egg may be in the oviduct. The oviduct is the tube that an egg travels along after it is released. People who use this method avoid intercourse around the time of ovulation. It is hard to get right because the timing of the menstrual cycle can vary.
- Surgical methods of sterilisation. In males, the tubes that carry sperm are cut or tied. In females, the oviducts are cut, tied or blocked so that eggs cannot reach the uterus. These operations are usually permanent.
Evaluating the methods
You may be asked to evaluate methods. This means you give advantages and disadvantages and then make a judgement. Useful points to compare are:
- How effective it is at preventing pregnancy.
- How long it lasts and whether it needs remembering every day.
- Side effects or health risks.
- Protection against sexually transmitted diseases.
- Whether it can be reversed, so a person can try for a baby later.
💊 The pill
Advantage: very effective when taken correctly.
Disadvantage: has to be remembered regularly, and gives no protection against disease.
💉 Implant
Advantage: works for months or years without daily action.
Disadvantage: side effects in some people.
🛡 Condom
Advantage: stops sperm reaching an egg without using hormones.
Disadvantage: can be used incorrectly.
✂ Sterilisation
Advantage: very reliable.
Disadvantage: usually permanent.
Worked example
Question: A woman often forgets to take tablets. Which hormonal method suits her better than the pill?
Answer: An implant, injection or patch. They release progesterone slowly to inhibit the maturation and release of eggs for a number of months or years, so there is nothing to remember every day.
Why science cannot answer everything
Science can tell us how each method works and how effective it is. But some issues around contraception cannot be answered by science alone. They involve ethical, social, religious and personal views. For example:
- Should contraception be freely available to everyone?
- Is it right to use methods that stop an embryo implanting?
- Should a person be sterilised?
People can look at the same evidence and still reach different conclusions, because their beliefs and values differ. Science gives the facts, but people make the decisions. Decisions about contraception also have personal, social and economic implications, for example the cost of a method or how it affects family size.
Exam-style question
(a) Describe how an oral contraceptive prevents pregnancy. [2 marks]
(b) A hormone implant is placed in the arm of a woman. Give one advantage of this method compared with the pill. [1 mark]
(c) Give one reason why a doctor cannot use scientific evidence alone to decide who should be offered contraception. [1 mark]
Model answer
(a) The pill contains hormones (1) that inhibit FSH production, so no eggs mature (1).
(b) It works for months or years, so there is no need to remember to take a tablet every day (1).
(c) Decisions involve ethical, social or religious views, which science cannot answer (1).
Exam tip
In part (a), name the hormone, FSH, and say what it stops: eggs maturing. "Stops pregnancy" on its own earns no marks.