An Australian prospective cohort study of risk factors for severe perineal trauma during childbirth.

Objective: to determine risk factors for the occurrence of severe perineal trauma (third and fourth degree tears) during childbirth.
Design: a prospective cohort study was conducted using the hospital's computerised obstetric information system. Additional data were gathered on women who sustained severe perineal trauma. Descriptive statistics and logistic regression were used to assess risk factors for severe perineal trauma. Midwives were asked to comment on possible reasons for severe perineal trauma. Written responses made by midwives were analysed using content analysis. Discussion groups with midwives were held to further explore their experiences.
Setting: Royal Prince Alfred Hospital, Sydney, Australia.
Participants: all women having vaginal births (n=6595) in a 2-year period between 1 April 1998 and 31 March 2000, in both the birth centre and the labour ward.
Measurements and Findings: 2% of women (n=134) experienced severe perineal trauma. One hundred and twenty-two women had third-degree tears and 12 had fourth-degree tears. Primiparity, instrumental delivery, Asian ethnicity and heavier babies were associated with an elevated risk of severe perineal trauma. Midwives identified several factors they believed contributed to severe perineal trauma. These were lack of effective communication with the woman during the birth, different birth positions, delivery technique, ethnicity and obstetric influences.
Key Conclusions: findings support current knowledge that primiparity, instrumental birth, heavier babies and being of Asian ethnicity are associated with increased rates of severe trauma. Specific attention needs to be paid to the strong association found between being of Asian ethnicity and experiencing severe perineal trauma.
Implications for Practice: further identification and validation of the concerns expressed by midwives to reduce severe perineal trauma is warranted so that preventative strategies can be used and researched.