Risk factors for severe perineal injury during childbirth: a case-control study of 60 consecutive cases.

AIM: The study aimed to evaluate the current risk factors for severe perineal tears in a single university-affiliated maternity hospital.

METHOD: An obstetric database of 31 784 consecutive women who delivered from January 2007 to December 2009 was screened for cases of third-degree or fourth-degree perineal tears. Four controls, matched by time of delivery, were selected for each case of third- or fourth-degree perineal tear. Maternal and obstetric parameters were analyzed and compared between the study and control groups.

RESULTS

Sixty women (0.25% of all vaginal deliveries) had a third-degree (53 women) or a fourth-degree (seven women) perineal tear. The control group comprised 240 matched vaginal deliveries without severe tears. Primiparity, younger maternal age, Asian ethnicity, longer duration of second stage of labour, vacuum-assisted delivery and heavier newborn birth weight were significantly more common among women who had third- or fourth-degree perineal tears. Of the variables that were found to be statistically significant in the univariate analysis, only primiparity (OR = 2.809, 95% CI: 1.336-5.905), vacuum delivery (OR = 10.104, 95% CI: 3.542-28.827) and heavier newborn birth weight (OR = 1.002, 95% CI: 1.001-1.003) were found to be statistically significant independent risk factors for severe perineal trauma.

CONCLUSION

Identification of women at risk may facilitate the use, or avoidance, of certain obstetric interventions to minimize the occurrence of childbirth-associated perineal trauma.