NEW YORK (Reuters Health) - If women are trying to conceive, they may have more success when they use the Clearblue Easy Fertility Monitor (Unipath), UK and US researchers report in the medical journal Fertility and Sterility.

"One known cause of failure to conceive is the mistiming of intercourse," Dr. Jayne E. Ellis pointed out to Reuters Health. Many couples only poorly understand their fertility cycle, she explained. "In our studies, only one quarter of women knew when their fertile days were."

Ellis, who is with the manufacturer of the Clearblue monitor, Unipath, in Bedford, UK, explained that the device utilizes a unique technology that measures two hormones in urine that increase in level in the days before ovulation. This "provides a wider window at which to target intercourse to achieve pregnancy," she and her colleagues explain in their report.

To determine how useful the fertility monitor might be, they studied 653 US volunteers who wanted to become pregnant. The participants were randomly assigned to use or not use the device at home over two ovulatory cycles.

The pregnancy rate was significantly higher in the monitor group at 22.7 percent than in the comparison group (14.4 percent).

Significantly more women who had been trying to conceive for less than 6 months became pregnant than did women who had been trying to conceive for longer.

Most users found the device easy and convenient to use.

"This study proves for the first time that identifying the fertile days of the cycle with a home test can really help women become pregnant over just two cycles of use," Ellis said.

The monitor, she concluded, "is a real step in improving a woman's chances of conception."