I've been looking into the studies that Scientology uses to support its silent birth practices. It says right there on their website "Studies show..." so I wanted to look it up.
The study they use to support their No talking, loud noises or bright lights practices is a Swedish study called "Obstetric care and proneness of offspring to suicide as adults: case-control study" 1998
( http://www.pubmedcentral.nih.gov/articl ... rtid=28715
It basically says babies with traumatic births are at risk of suiciding as adults. It also found that babies of mothers who took opiates near birth are less likely to violently commit suicide.
Of course this doesn't prove silent birth is effective, because traumatic births (listed as: presentation other than vertex, meconium stained amniotic fluid and membranes, instrumental delivery or internal version, and resuscitation and other complications usually requiring ward care.) are usually not purposely done.
Another study I read suggested that lack of oxygen to the brain before, during and after birth, when the baby switches from umbilical cord to lungs, might be the cause of some mental diseases that lead to suicide.
http://bjp.rcpsych.org/cgi/content/full ... ;189/6/502
Also this "High cortisol levels in utero could have a lifelong influence on the hypothalamic–pituitary–adrenal axis, resulting in hypercortisolaemia in adulthood, which has been linked to depressive disorders", cortisol being from stress I gather.
The silent birth case all hinges on whether babies can remember words during birth, which I gather is supposed to lead to them remembering the trauma associated with these words and reacting negatively.
So why not just get foreign language doctors?