Three-dimensional ultrasound of the pelvic floor 2 days after first delivery: influence of constitutional and obstetric factors.

OBJECTIVES: Morphological changes of the pelvic floor during pregnancy and delivery can be visualized by three-dimensional (3D) perineal ultrasound. The aim of this study was to compare biometric measurements of the levator ani muscle according to maternal constitutional factors, delivery mode and size of the baby immediately after the first delivery.
METHODS: In this prospective observational study, 130 primiparae were recruited (all of them Caucasians with singleton pregnancy and cephalic presentation). A 3D perineal ultrasound scan was performed on the second day after delivery with standardized settings. Volumes were obtained at rest and on Valsalva maneuver, and biometric measurements of the levator hiatus were determined in the axial plane. Different obstetric and constitutional parameters were obtained from our clinical files.
RESULTS: All biometric measurements of the levator hiatus were significantly greater in the vaginal delivery group than in the Cesarean section group (P < 0.001), whereas subgroup analysis within the vaginal (spontaneous vs. operative vaginal) and Cesarean (primary vs. secondary) delivery groups did not show statistically significant differences. There was no demonstrable influence of maternal constitutional factors (age, body mass index (BMI)) or different obstetric parameters (length of second stage of labor, episiotomy, maternal injuries) on levator hiatus size postpartum, even in subgroups that delivered vaginally. Women with de novo postpartum stress incontinence showed a significantly higher mean levator hiatus transverse diameter and larger hiatal area on Valsalva maneuver (P < 0.05). There was also a positive but very weak correlation between the newborn's head circumference and hiatal dimensions at Valsalva maneuver (P < 0.05).
CONCLUSIONS: Pelvic floor imaging by 3D ultrasound is easily accessible even on the first days after delivery and can provide useful information on morphological changes of the levator ani muscle. In our study, women with vaginal or operative vaginal delivery had a significantly larger hiatal area and transverse diameter than women who delivered by Cesarean section. Maternal constitutional factors (BMI, age) and duration of second stage of labor had no influence on the biometric measurements of hiatal area, whereas weight and head circumference of the baby showed a positive correlation with area of the levator hiatus. Copyright 2010 ISUOG. Published by John Wiley & Sons, Ltd.