Yes when you test it detects the LH surge that preceeds ovulation. The problem is that many women can have LH surges that do NOT preceed ovulation. This is more common in women that have come off of birth control in the last year, women who are breastfeeding and women who are of advanced maternal age but it can and does happen in ALL women.
The only way to know if the OPK was right other than waiting to see if you get pregnant is to chart BBT along with it but if you are charting BBT you might as well be charting cervical mucus and cervical position.
I know for many women charting seems scary or it seems like there is a lot of work involved but it's really not. It takes less than 3 minutes a day to check CM, CP and BBT. Then you just chart it on one of the many FREE charting sites such as www.fertilityfriend.com. Plus it's extremely empowering to understand your body better.
at 11:47 AM on Nov. 12, 2010