Methods of Ovulation Prediction

Women who know their menstrual cycle and approximate ovulation date can maximize their chances of conceiving. The oocyte, which is released during ovulation, can live 12 to 24 hours, while sperm can live 48 to 72 hours. That said, the ideal time for intercourse is somewhere between 3 days before ovulation and no later than 24 hours after ovulation.

Basal body temperature method

Basal temperature is the temperature of your body at rest. To track your temperature, it is recommended that you purchase a digital thermometer with one-tenth degree increments. These highly sensitive thermometers will allow you to detect even the slightest fluctuations in body temperature. When charting your basal body temperature, you must take your temperature as soon as your wake up, before getting out of bed, and preferably at the same time every day. Temperature can be taken orally, intravaginally or rectally.

A woman's basal temperature cycle is divided into 2 phases:

1. At the beginning of your menstrual cycle, your body temperature is lower, with a maximum around 36.7 °C (98.1 °F). You may even notice a sudden drop in temperature 12 to 24 hours before ovulation.
2. Once ovulation has occurred, progesterone is secreted, causing a rise in temperature of about 0.2 to 0.6 °C.

By recording your daily temperature readings over several cycles and plotting the results on a graph, you will be able to pinpoint the date on which you typically ovulate. Ovulation usually occurs on the last day of low temperatures.

The basal temperature method is useful to confirm that ovulation has occurred but predicting it is more complex.

Cervical mucus method (Billings method)

Cervical mucus is a fluid that is secreted from the cervix. Hormones are behind the changes that occur in the consistency of cervical mucus throughout the menstrual cycle. By observing its appearance and texture, you can determine when you are ovulating. About 5 to 6 days before ovulation, as estrogen increases, you will notice that in addition to an increase in the amount of cervical mucus, it also becomes clearer and more slippery. Its texture typically resembles that of a raw egg white and it usually stretches between your thumb and index finger. As ovulation draws nearer, the mucus becomes even more elastic and clear. After ovulation, and as progesterone levels increase, the mucus thickens, becomes cloudy or pasty and production decreases. As is the case with basal temperature, its often the next morning, when the mucus thickens or disappears that one realizes that ovulation has occurred.

Sympto-thermal method

This method combines the two above mentioned methods.

Saliva ovulation microscope

During a woman's fertile period, the salt content in body fluids, including saliva, increases with the rise in estrogen. By carefully examining the appearance of your saliva under a microscope, you can determine whether or not you are fertile on a given day. During non-fertile periods, there are bubble-like structures in the saliva, whereas during fertile periods, the saliva patterns look like ferns.

Urine Ovulation Test (LH)

These tests are used to help predict ovulation based on the amount of LH (luteinizing hormone) in urine. The series of tests should start 2 to 4 days before the predicted ovulation date. A test should be performed at the same time every day until the results are positive. A positive test result indicates that ovulation will occur within the next 12 to 36 hours. Clearblue, First Response and Conceive are examples of products you can purchase at your local pharmacy.

Urine fertility monitor (LH/estrogen)

This type of monitor determines the presence of two hormones: luteinizing hormone and estrogen. By identifying these two hormones, the device can predict ovulation and indicate the level of fertility at the time of the test. Several urine tests must be performed (for about 20 consecutive days) so that the device can record baseline hormone levels and then identify fertility periods based on hormone fluctuations.

For more information:

• The Society of Obstetricians and Gynaecologists of Canada