Yes, they do. According to the American Fertility Association to release an egg. And that spells , the best over-the-counter kits measure luteinizing hormone (LH), which can be detected in your pee stream. The presence of LH means that the brain is telling the ovaries j-a-c-k-p-o-t.
These kits aren’t like Twinkies, though — they won’t last forever. They’re usually only effective for two years, so be sure to look at the expiration date. Prices range from about $14 to $25, depending on brand. Most come with a five-day supply of sticks, to be used in as many days. Your job: Pee on the stick, and wait for a line to appear. If its color is the same as the shade indicated by the instructions, ovulation is imminent (within 24 to 48 hours). If it’s too close to call, retest within the next 12 hours.
If you’re having a hard time with the ovulation predictor kits (is it the exact color on the box?), try a small electronic monitor. It can read the results for you, and tells you even earlier when to expect a surge in LH. The monitor can get expensive, though, (you have to keep buying new sticks to pee on) so weigh the pros and cons before you open your wallet.