Luteinizing hormone (LH) plays a major role in ovulation. The level of LH increases dramatically as ovulation approaches.

Ovulation detection kits test for the LH in your urine. The test is positive when LH levels are high enough to trigger ovulation.

Studies show that ovulation detection kits are reliable but cannot tell you the exact moment when you will ovulate. Although the price of these kits varies between $25 and $50, these kits can help you more accurately predict the day of ovulation. They are more likely to be used by women who desire pregnancy, but they also can be used to help avoid pregnancy.

Advantages

• When used accurately, this method of natural family planning and periodic abstinence has a pregnancy rate of 2 percent to 3 percent (as long as sexual intercourse is avoided during the fertile period).
• This method does not interrupt or alter fertility. Pregnancy is possible as soon as this method is abandoned.

Disadvantages

• When used imperfectly, these methods have a pregnancy rate as high as 84 percent.
• The test kits are expensive.
• Because of normal variations in the menstrual cycle and in the lifespan of eggs (one to three days) and sperm (two to seven days), you will need to abstain from intercourse for a number of days, including those immediately around ovulation, to be safe.