For conception to occur we must start with an ovum and semen that contains sperm. The semen must be deposited in the vagina so that sperm may travel through the cervix (neck of the womb), uterus and tube to fertilise the ovum. The fertilised ovum must then be able to pass down the tube to the uterus, where the endometrium (lining of the womb) must be in the right condition for it to implant and grow.
Contraception is any action taken to prevent conception. First let’s discuss exactly what is meant by ‘contraceptive effectiveness.’
Contraceptive effectiveness
Studies on the effectiveness of any one contraceptive method give variable results. Results are influenced by many things: how many people are studied and for how long; the age (and thus the fertility) of the people studied; their frequency of sexual intercourse; their motivation for preventing pregnancy; how well they are taught to use the method.
The intentions, beliefs and honesty of; whoever is performing and reporting on the study can also influence the results. There are plenty of stories of investigators planning study methods and analyses of results to favour a method in which they had vested interests – moral or financial.
When choosing a method, you’ll want to know how effective it is likely to be for you. Effectiveness is usually stated as £ percentage success or failure. What do these figures mean?
Measuring contraceptive effectiveness
There are two ways of measuring the effectiveness of a particular method in preventing pregnancy.
• Method-effectiveness,
also called theoretical effectiveness, measures the efficacy of a method when it is used exactly as it should be. As long as the quality of products used is standard, method-effectiveness varies only because of physiological differences (such as decreasing fertility with age) between the people who use it.
•Use-effectiveness takes into account the mistakes that can be made in using a method, and varies much more according to the method of study and people studied. With the exception of sterilisation and IUDs, all methods rely on users for their effectiveness. Both method- and use-effectiveness are usually expressed as failure rates per hundred woman-years of use, that is, the number of pregnancies that occurred in that study among each hundred women who used the method for 12 months. In other words, failure rate gives you a rough idea of your risk of accidental pregnancy when using a particular method of contraception for a year. But if the method you choose never lets you down it’s 100 per cent effective for you; if you have an unplanned pregnancy you could consider the method a total failure.
Choosing contraception
This very important choice may be easy or difficult. The more you know about all methods – how they work, their efficacy, possible side-effects, advantages and disadvantages – the easier it will be for you to choose a method likely to suit you.
Your choice will depend on many things: your age, whether you already have children and whether you want more, how often you have sex, past experience with contraception, your general health, perhaps your religious and political beliefs. Your attitude to each method will also be influenced by what your family and friends have told you, the attitudes and beliefs of providers of contraceptive service and the news media. News reports about contraception may be sensational and misleading. If you hear something that worries you, check with your doctor, the Family Planning Association or another reliable information source to make sure that the report was accurate and balanced.
The ideal contraceptive hasn’t yet been discovered. Though some methods suit some people very well, there’s not yet a method that’s suitable for everybody and it’s uncommon for a single method to suit the same person throughout her or his reproductive life.
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