If fear and anxiety leads to birth complications then would you expect naturally anxious people to have a higher incidence of traumatic births wherever the births take place.
I think that there is a certain amount of evidence which would be consistent with this theory, but I don't think its been 'proven' as such. I've seen a couple of studies along these lines, so it does seem to suggest there is a certain amount of self selection going on which we shouldn't discount as a cause of differences between home and hospital births. I'm not sure just how good the studies below are but they certainly do raise a few worthwhile questions if nothing else.
The influence of women’s fear, attitudes and beliefs of childbirth on mode and experience of birth - Helen M Haines, Christine Rubertsson, Julie F Pallant and Ingegerd Hildingsson 2012 reported this:
Three clusters were identified – ‘Self determiners’ (clear attitudes about birth including seeing it as a natural process and no childbirth fear), ‘Take it as it comes’ (no fear of birth and low levels of agreement with any of the attitude statements) and ‘Fearful’ (afraid of birth, with concerns for the personal impact of birth including pain and control, safety concerns and low levels of agreement with attitudes relating to women’s freedom of choice or birth as a natural process).
At 18 -20?weeks gestation, when compared to the ‘Self determiners’, women in the ‘Fearful’ cluster were more likely to: prefer a caesarean, hold less than positive feelings about being pregnant, report less than positive feelings about the approaching birth and less than positive feelings about the first weeks with a newborn.
At two months post partum the ‘Fearful’ cluster had a greater likelihood of having had an elective caesarean; they were more likely to have had an epidural if they laboured and to experience their labour pain as more intense than women in the other clusters. The ‘Fearful’ cluster were more likely to report a negative experience of birth. The ‘Take it as it comes’ cluster had a higher likelihood of an elective caesarean.
Another earlier study in Sweden from 2011
Found that fear of childbirth affected obstetric outcomes and increased the frequency of emergency and elective cesarean sections. Induction of delivery was more common among the women with fear of childbirth (16.5%) as compared to the women without this problem (9.6%). Women with fear of childbirth who were scheduled for vaginal delivery were more often delivered by emergency cesareans and they also more often requested elective cesarean delivery.
Its all also very consistent with observations and theories from pro-natural childbirth campaigners with regard to the importance of oxytocin and being relaxed in childbirth.
So I do think its VERY important we don't get too carried away with pushing women down certain routes, and really do get to the heart of why there is this difference between home and hospital births in seemingly comparable low risk women. .