Fertility charting - taking your body basal temperature first thing each morning and recording the readings on a chart - has long been used to aid natural contraception. Now, however, it is being used more and more to aid a natural conception where fertility problems have been encountered.

If you are to maximise your chances of conception then you should use fertility charting, but it's easy to use it ineffectively and obtain misleading information. This article sets out the most common errors in using this system and how to use it properly so as to get highly accurate readings that will help you pinpoint exactly when your body is at its most fertile.

1. Use a proper BBT thermometer. The thermometers we use to measure our body temperature when we have a cold or the flu aren't accurate enough for measuring basal temperatures. BBT thermometers are accurate to within 0.1 degrees and you should rely on nothing less.

2. Take your temperature at the same time each morning. This is vital, yet is often overlooked by women desperate to get pregnant. You need to have been asleep for at least 5 hours. No doubt you know about the need to take your temperature before you do anything else - even go to the bathroom - but the time you do this is just as important. This includes weekends, of course, so perhaps a little sacrifice in the way of lie-ins is called for.

3. Note the reading immediately, in writing. No relying on memory after you've gone back to sleep for a few minutes. Transfer this to your chart as soon as you can, and review the latest data for any signs of an increase in your body's fertility. If there were any unavoidable changes in the way you took the reading, e.g. you were a few minutes later than usual, then note that fact on your chart.

4. Take a vaginal reading rather than an oral one, for much greater accuracy. There can be external factors influencing the exact temperature reading from your mouth, e.g. a cold developing, or having slept with your mouth open. Use the same actual thermometer for every reading to avoid the possibility of anomalies between different thermometers, even of the same make and type, and use the same method of taking the reading as well.

5. If you are really serious about getting pregnant you will most probably be avoiding alcohol consumption or, indeed, anything that might cause an obstacle to your plans for pregnancy. However, if you have a lapse in this regard then note it on your chart as it may be responsible for any variation from your normal pattern of readings.

Although most women have the best part of a week to get pregnant, this does vary and it may be that the difficulties you have had are simply down to bad timing. Use the fertility charting method as I've described to give yourself the best fertility help possible and the best possible chance of timing things right.