Answer to the question about silent births, WARNING! serious wall of text approaching.
Ok, so I am making my way through the papers, and typing this as I finish each one. Each new paragraph is either a new paper or idea that sprung into my mind for further study.
Keep in mind on the "Obstetric care and proneness of offspring to suicide as adults: case-control study" paper, this type of research is even less sure fire than most research done. Research like this never proves anything, but only indicates something. Although the same can be said for all other research, in most cases it would possible to beat you over the head with enough hard facts to make you take it as the truth, in this case even those facts need to be backed up with more facts, and so on. So this is not really a good example of something you should base your entire argument on.
Secondly; This study says absolutely nothing about speech or any other factor. What was discussed was level of pain in mother; through using opiates to lessen the pain, and complications that might arise during birth increasing the pain due to surgical methods of getting the baby out. Being male I probarbly can't state much about this, but if a baby is affected by the mothers pain, a silent birth would only add to this pain, at least mentally. Or so I would assume.
A point made in the research paper was a bit more interesting though. There is a possibility that mothers whom have had painful labours are less concerned for that child. This could account for the results the study shows, but this woul also depend on many other factors.
The "Perinatal circumstances and risk of offspring suicide" paper seems to confirm this last view. It was not as specified on the stress factors during birth, but took a lot more of the confounder factors into account, such as; number of children in familly, age of mother, profession, etc. And makes a conclusion that these seem to make quite a bit of difference in conjunction with complications during birth. A child well cared for is less likely to commit suicide.
It does touch upon an issue within genetics that I have devoted quite a bit of thought to; that genes are controlled as much by emotional factors as they are any other. (If you want a further explenation please ask, because it will be a rather lengthy post to get all of it covered.)
A paper on sociology connected with biology and evolution can be found here;
I have not gone through it in its entirety, but be prepared for a lot of scientific terminology and heavy thinking on this one.
On a whole, from a couple of other papers I have looked into, it can be said that while the brain is in development it is probarbly in its most fargile stage as being potentially affected by psychological disorders. To make the claim that these all are the result of direct physical trauma on the child would be ludicrous. There are all too many factors present for mantal trauma, like feeling abandoned by a mother whom is still subconciously blaming the child for causing so much distress, that are far more likely to affect a child, even genetically. Silent births are more likley to cause long term distress in the mother, and such a feeling of blame, moreso than the child hearing screaming as it is being born.
I would assume that this view form the Scientologists correlates with their view on how a person in a car accident hearing something will later be affected by this, and the best way to handle it would be to keep your mouth shut and not let anyone know that they look dead. Which is an absolute load of bullshit, since a memory or emotion can not affect biochemistry in a way that would cause cell death.