
Sorry, I'm not Terri, but just in case she doesn't pick up....
Yes, you test the vaginal mucus, and when the strip turns colour to a sort of dark browny-purple-reddish (!) I believe you need to serve the bitch in about 48 hours.
However, like all of these tests, it's not 100% foolproof by any means. Son did a thesis on it when he was at college, and spent a long time proving it didn't work all the time (!!!)
Expect Terri can tell you more
Jo and the Casblaidd Flatcoats