If you are right in the middle of planning for a child, you would naturally like to make effective use of the scarce time available in everyday life and not miss a single opportunity. The fertility window exists only once per cycle and the maximum fertility only on one day.
Many couples chase after this point in time and ovulation tests are used in the hope of accurately determining ovulation. Only here lies the common misconception that a test can determine or predict the exact time of ovulation. Many people imagine that after the morning test, the result would be ovulation YES or ovulation NO. However, this is not the case. Ovulation tests measure the concentration of certain hormones in the urine. Shortly before ovulation, the concentration of these increases. This means that one should start testing early enough and regularly so as not to miss this fluctuation, especially since the test device has to determine a zero line to the test strip in order to recognize an increase as such at all.
In summary, this means that ovulation tests do not determine the time of ovulation, but indicate the probability that ovulation will take place or has taken place. So it is not the WHEN but the OB that is displayed. There is no absolute value that can be used to indicate the ovulation with 100% certainty. Since it is however an increase to a basic value, which can be different by the way with each woman, must be measured constantly, or tested, depending upon method which one selected.