Sometimes a woman's temperature does not rise with ovulation, or there are other difficulties with using the basal temperature method of predicting ovulation. If you find yourself in this condition, there are a variety of products available from the drug store which can help you predict "O-day," but they can be a costly alternative.

What's included in an ovulation prediction kit, and how does it work? Actually there are several types of ovulation predictors. One of the choices is a battery operated device that tests your saliva for the presence of hormones which indicate ovulation. These testers are reusable and are about the size of a lipstick. Using one requires you to put a drop of saliva on the lens. When it dries, you have an eyepiece through which the dried saliva is magnified forty times. If increased estrogen is presence, the saliva will have dried in a fern-like design. Such a device can cost around $40, but it doesn't require additional purchases. Brand names include Ovulite and Fertile Focus.

Another option is a kit that requires you to collect your urine in a cup and test it with a test strip to determine the presence of hormones. Most of them test for luteinizing hormone, a substance that increases prior to ovulation. There are a variety of these kits on the market. Some have as few as 7 test strips included and others have 20 or more. For women with irregular periods, seven test strips might not be enough. One of these kits will probably cost between $15 and $30. If you need to buy one several months in a row, it could prove costly. However, they are helpful and somewhat less trouble than charting basal temperatures, although many women do both at the same time. Brands include Answer and Clear Blue.

If money is not an object and you like high tech gadgets, you might want to check into an electric fertility monitor with a digital read-out. For $200 you can get a small device that will tell you when to test your urine, based on the first day of your period. The monitor also reads your test sticks for both luteinizing hormone and estrogen. One such device is made by Clear Blue. If pregnancy doesn't happen within a few months, you will have to buy additional test strips to use with it.

Clear Blue also makes a tester that has a digital readout that is very easy to interpret, unlike some other kits. It costs about $40, can test urine seven times, and is not reusable - which makes it too costly for a lot of people.