You can see and feel cervical fluid around ovulation time. (floliving.com)
The app utilizes a very advanced algorithm to identify exact ovulation time and thus, tells you specifically when you need to use protection to prevent a pregnancy. (ultrawellnesscenter.com)
So if they test each day, the day that's it's positive that's when they have intercourse that day and the next day and they'll be hitting right at ovulation time for pregnancy occurrence. (kidsinthehouse.com)