Purpose: This study was conducted to evaluate the prevalence of perineal trauma during childbirth and to assess the correlations of the pelvic floor dimensions and fetal head station with obstetric trauma in a prospectively recruited cohort of women. Methods: The study included women with a gestational age of at least 37 weeks, who were carrying a single fetus in a cephalic presentation. Transperineal ultrasound (TPU) was performed prior to the onset of labor or labor induction. The purpose was to measure the anteroposterior diameter (APD) of the levator ani muscle (LAM) and the angle of progression, at both rest and maximum Valsalva maneuver. The head-perineum distance was assessed only at rest. Results: A total of 296 women were included. Of the 253 women who delivered vaginally, 19.0% (48/253) experienced no perineal trauma, 18.2% (46/253) received an episiotomy during childbirth, 34.4% (87/253) sustained a first-degree laceration, 25.3% (64/253) had a second-degree laceration, and 3.2% had a third-or fourth-degree laceration (8/253). Women with episiotomy had a significantly shorter median APD under Valsalva than women without perineal trauma. Furthermore, women with LAM coactivation (identified by a negative difference between the APD at Valsalva and the APD at rest) were approximately three times more likely to undergo an operative vaginal delivery and over five times more likely to sustain a third-or fourth-degree tear during childbirth than women who exhibited normal relaxation of the LAM during the Valsalva maneuver. Conclusion: TPU may predict the risk of perineal trauma in women with term pregnancy during childbirth.
