They offer them every week starting at 36 at most places, but I'll be refusing. Honestly, they don't tell the doctors anything they'll use to make informed medical decisions. Your cervix can be soft and open for a long time without going into labor and you can have a very non-labor-friendly cervix at your checkup and go into labor that night. I've started to wonder if the practice didn't become common because it make impatient mommies feel like their OBs were doing something useful instead of just going into an appt to have the doctor say, "yup, you're still pregnant, see you later". The number of women who look forward to finding out their cervix status each week is a little weird to me, but I get the anticipation that they associate it with impending baby time.