BACKGROUND: There are a number of poor birth outcomes with advancing maternal age. Although there is some evidence of a higher risk of trauma to obstetric anal sphincter and the levator ani muscle with advancing age, findings to date are inconclusive.OBJECTIVE: The aim of this study was to assess the risk of pelvic floor injury using translabial 3- and 4-dimensional ultrasound relative to advancing maternal age in primiparous women after a singleton vaginal delivery at term and to determine any association between maternal age and obstetric trauma, including obstetric anal sphincter injuries, levator avulsion, and irreversible overdistension of the levator hiatus.STUDY DESIGN: This is a subanalysis of a perinatal intervention trial conducted in a specialist urogynecology referral unit at 2 tertiary units. All primiparous women with singleton birth at term underwent 3- and 4-dimensional translabial pelvic floor ultrasound both ante- and postnatally for the assessment of the obstetric trauma including levator ani muscle avulsion, hiatal overdistension to 25 cm 2 or more, and obstetric anal sphincter injuries. A multivariate logistic regression analysis was performed to examine the association between maternal age and obstetric trauma diagnosed on 3- and 4-dimensional translabial ultrasound. Multiple confounders were included, and the most significant ( forceps and vacuum delivery) were used for probability modeling.RESULTS: Of 660 women recruited for the original study, a total of 375 women who had a vaginal delivery with complete data sets were analyzed. A total of 174 women (46.4%) showed evidence of at least 1 form of major pelvic floor trauma. Advancing maternal age at first delivery carries with it a significant incremental risk of major pelvic floor trauma with an odds ratio of 1.064 for overall risk of injury for each increasing year of age past age 18 years (P = .003). The probability of any type of trauma appears to be substantially higher for forceps delivery. Vacuum delivery appears to increase the risk of obstetric anal sphincter injuries but not of levator avulsion.CONCLUSION: There is a significant association between the risk of major pelvic floor injury and increasing maternal age at first delivery.