If you're planning a pregnancy, you're probably tracking your ovulation, the monthly peak in your fertility when the egg leaves the ovary -- and, with any luck, connects with a sperm. It usually occurs about 14 days before your next period.

New Tests To help perfect their baby-making timing, many couples enlist the aid of over-the-counter ovulation tests, which measure the levels of luteinizing hormone in urine. New ones, which use saliva to indirectly measure estrogen levels, are just as accurate and more convenient.

But Do They Help? An ovulation test isn't necessarily the best gauge of fertility, say experts. One problem: If you rely on one to pinpoint to the day the perfect time to have sexual intercourse, you might actually miss some of your fertile days, finds Donna Day Baird, Ph.D., an epidemiologist with the National Institute of Environmental Health Sciences. She's found that the "window of fertility" -- between days 10 and 17 of the cycle, beginning in the five days before ovulation¿ -- may be too narrow. In Baird's study of 213 women who all had regular cycles, 70 percent had a fertility peak earlier or later.

The best way to get pregnant, she says: "Have sex two to three times a week, and you'll have the time period covered."