DH's was more a cone the other way front to back (rather than top to bottom) - so much so the paed had us propping his head so he couldn't roll it to the side to try and get it to flatten if there was enough movement left in the plates. I was given the impression by medical people that due to the fusion in his plates they wouldn't have been able to move enough to get the "standard" cone shape and thus would have been a hinderance in the birthing process (true?? I don't know).