I found this study pretty interesting, I thought C-Section was the way to go, but it seems that vaginal birth despite the stress may be less risky. It was presented at the Society for Maternal/Fetal Health
https://www.healthyus.com/blog/2012/02/c-section-vs-vaginal-birth-for-premature-babies/
https://www.healthyus.com/blog/2012/02/c-section-vs-vaginal-birth-for-premature-babies/