This question keeps coming up, no matter how many times its answered. Cervixes are muscles intended to keep a baby inside a womb for 36-40 weeks. Not only is it strong enough to accomplish that under many difficult conditions, it is also strong enough to keep things OUT...again, under what can be difficult conditions. Unless your "dog" is a llama, his cock does NOT turn corners. Wishful thinking will never make a straight line turn left, right, up or down. At the risk of some smartass joking about it....it is not a joystick. Any simple anatomy drawing will point up what is and is not going to happen. The front few inches of a dog pecker swells away from the os, sideways and forward....the bone does not move with it, beyond initial penetration. Once forward of the bone, the penis is softer, far less rigid. If he actually reaches the cervix mouth, his pecker tip will slide PAST it, not into it; all the angles are wrong. Perhaps this us why some women are convinced it penetrated....it would mimic how the obgyn's fingers feel.
And consider this. If the doggie did manage to poke that little donut, hes going to hit it ONCE, and dismount in a hurry. Way too many people here are getting their "knowledge" from fiction and fantasy. Hit that little mouth and SHE'LL kill you....The dog will be utrpfq, because his cock HURTS. Pain is a great discourager of bad behavior and wrong moves. Dogs, unlike people, rarely make the same mistake twice.
I dont care WHAT the girl says....if she hasnt been physically modified, it did not happen.