CLEVELAND -- Many women who have trouble getting pregnant turn to ovulation kits to help them predict the best time to conceive.

But some tests are better than others. In Monday's Consumer Alert, Troubleshooter Chris Caswell reported on which ones you can trust.

Nine-month-old Hannah didn't happen by chance. Like more and more women, her mother used an ovulation test to take the guesswork out of getting pregnant.

"We were anxious to try (to) have a baby," said Ellen Hirsch, Hannah's mother. "We just decided (that) it had been a couple of months -- why not use it?"

Consumer Reports took a close look at 11 ovulation test kits. Tester Nancy Metcalf said they all work the same way.

"These kits are designed to detect a certain hormone in a women's urine," she said. "It's called luteinizing hormone, or LH. It surges to high levels a day or two before women ovulate."

A woman will know when the LH surge is occurring by checking the lines that appear in the window of the test stick. She will usually need to test for several days before she gets a positive reading, so most kits contain five or more sticks.

"We use various concentrations of LH to test the kits, because concentrations of LH vary in women. We found that some kits were far less sensitive than others," Metcalf said.

Two kits could miss the LH surge in many women. They're the First Response pregnancy planning kit and the Answer One-Step ovulation test.

"The best kit we tested was sensitive enough to detect the LH surge in about 88 percent of women," Metcalf said.

Metcalf said the best kit was the Clear Plan Easy ovulation test pack. It costs $30 and includes seven test sticks.

Hannah's mother said the ovulation test kit worked for her, and she has the little one to prove it.

Ovulation tests may be helpful for women having difficulty conceiving, but most women don't need them.

Health studies revealed that, after a year of unprotected sex, 85 percent of women get pregnant.