In doing my research I stumbled across a few useful resources which I have listed below. There wasn’t a great amount of literature on recurrence rates (hence the inspiration to carry out my survey in the first place) but you might find these websites helpful nonetheless.
Preconceptual counseling of women with previous third or forth degree tears
Patterns of maternity care in English NHS hospitals 2011/12
Third Degree Tears – Management of the next birth
Evidence Based Birth – What is the evidence for perineal massage to prevent tears
RCOG – Management of third and forth degree perineal tears
RCOG – A third- or fourth-degree tear during childbirth – information for you
Midwife’s Guide to an Intact Perineum
Midwifery Matters – Perineum an Perineal Tears
Midwife thinking – perineal protectors
Hands on or Hands Off – Debate by Helen Young Midwife
3rd & 4th Degree Tears 