Menstrual cup to catch first trimester spotting

has anyone else used a menstrual cup to catch early spotting. it started as brown discharge so I inserted my cup and after 12 hours I had about 15 ml of red blood with minimal clotting. I am wondering if I had not used the cup the red blood would have stayed inside longer, turning brown before eventually discharing. my theory is that I'm not spotting red... but because my cup is in place the blood is not turning brown. Can anyone confirm or deny this?