The test paper does not turn negative immediately after the egg is released. Ovulation is an instantaneous process, but it takes a few days for the hormone levels to drop, so the test paper will slowly change from two bars to one bar, which also takes time. It takes about five days from the time of ovulation until the test paper turns negative, which means that the test paper starts as a strong positive, then turns weakly positive and then negative, which is a normal evolution. Women who want to improve the chances of conception can use ovulation test paper to conduct self-tests during the ovulation period or monitor ovulation through ultrasound in the hospital and arrange sex, which can greatly improve the chances of conception.