...been dealing with pregnant sheep most the day (I live on a farm)...back to humans....I think you may be onto something. This lends weight to your suggestion:
"The cervical canal, which forms part of the birth canal during childbirth, dilates ( expands) widely to allow passage of a baby. The bulk of the cervix ... There are four fornices, two lateral, plus anterior and posterior"
http://www.daviddarling.info/encyclopedia/C/cervix.html
Also "posterior cervical canal" also brings up "despression of", presumably by using fingertips (or similar instrument). Basically, your suggestion certainly convinces me given what else I've seen and quoted here.