Testing & Timing

When you are trying to conceive, getting pregnant becomes more than just having sex. In order to improve your chances of pregnancy, it is important to start keeping track of when you ovulate so that you can be sure to have intercourse at your peak fertile time.

Timing Intercourse and Pregnancy Testing

Many couples wish to try and time intercourse to the most fertile part of the cycle. It is certainly true that there are only a few days where pregnancy can occur and it does seem an attractive idea to try and get it right. Unfortunately, studies that have compared timed intercourse with just having sex two to three times per week have not found that doing this actually improves conception rates. It is known that sperm quality deteriorates with more than 10 days abstinence and after some months timed intercourse can become psychologically draining.

The most common way of checking for ovulation is to measure the basal body temperature (BBT), looking for the slight rise at the time of ovulation. Another, albeit expensive, alternative is to use the urine testing kits which look for the peak of the hormone LH (luteinizing hormone) which triggers ovulation. Studies comparing these methods have found that the LH test correctly identifies the day of ovulation about 60% of the time and BBT around 43%.

Sperm remain inside and capable of fertilisation for several days or more, but the egg is only around for 24 hours. Studies looking at the pregnancy rate in relation to the day of intercourse have found that the fertile period starts 5 days before ovulation and ends on the day of ovulation, with the greatest chance of success being 2 days prior to ovulation. Having intercourse after ovulation does not result in pregnancy.

Considering the above, it is not surprising that timing intercourse is not helpful - the rise in BBT is a sign that ovulation has occurred and by that time you have missed the boat! Even if a woman has very regular cycles and can predict when she expects the BBT rise, this indicator of ovulation will only be right less than half the time.

When to Check Temperatures

The use of a BBT chart for a couple of cycles is certainly useful, however, to check that ovulation is taking place, even if it can't exactly predict the actual day. You will need a thermometer with markings to the nearest 10th of a degree (preferably in centigrade scale) - this is available from most pharmacies.

You should start on the first day of your period, checking your temperature at the same time each day just after waking up and before drinking anything. This is plotted on a chart and ovulation is confirmed when the chart shows a sustained rise in temperature of around half a degree for 14 days before the period. Ovulation is presumed to have occurred on the last day before the temperature rise. An example of an ovulatory cycle is shown on the chart. The hormone progesterone is responsible for this rise in temperature.




A better predictor of impending ovulation is the change in cervical mucus a few days before ovulation. This pre-ovulatory change is due to the hormone estrogen. By placing two fingers into the vagina toward the cervix, wiping around and removing them, you will notice that the mucus becomes a profuse, clear, stretchable, watery secretion. Remember that cervical mucus change is not itself a sign of ovulation and if you wish to confirm that your cycles are ovulatory, it is necessary to use a BBT chart or urine LH kit.

If you are really keen to do something with regards to timing, the best approach would be to use the BBT method for a few months to check that ovulation is taking place, and then ensure that you have intercourse around the time of the change in cervical mucus, but not exclusively then.

Pregnancy Testing

Modern pregnancy tests available 'over the counter' are as accurate as those done at the chemist or in your GP's surgery - indeed, they probably are the same one. They are very sensitive to the hormone of pregnancy - hCG (human chorionic gonadotrophin) and can be positive a few days before the missed period. An early morning urine is usually the most concentrated and will improve the pickup. Many women find that they have a positive pregnancy test one day but a few days later they start their period, or it becomes negative. The earlier that pregnancy is detected, the more miscarriages are found.

Testing with extremely sensitive pregnancy tests has found that as many as 1 in 2 or 3 pregnancies do not carry on. Some call this a 'biochemical pregnancy' as it was never clinically recognised. Conversely, some women have a negative test after a missed period and then it goes on to be positive and the period never comes. This may be related to delayed ovulation in that particular cycle, or because the pregnancy test was not sensitive enough. They are only 99% accurate, after all. It is advisable to wait at least a week after a missed period for a reliable answer to that question, but often the suspense is often just too much to bear!

Find more information on becoming pregnant at Trying to Conceive.