Ultrasound of the pelvic floor during and after first pregnancy

Abstract

Objective

First, to evaluate the reliability of different assessments using three/four-dimensional (3D/4D) transperineal ultrasound in women during and after their first pregnancy. Second, to describe changes in pelvic floor anatomy and function during and after first pregnancy and to provide insight into the role of the levator ani muscle in the development of pelvic floor dysfunction and in progress in labor.

Methods

In this prospective observational study, 280 pregnant nulliparous women were examined by 3D/4D transperineal ultrasound at 12 weeks’ gestation, 36 weeks’ gestation and 6 months postpartum. Bladder neck position, levator hiatal dimensions (anteroposterior diameter, transverse diameter and area), the levator-urethra gap (LUG) and the presence or absence of levator avulsions were determined offline. Symptoms of pelvic floor dysfunction were assessed using the Urogenital Distress Inventory. Delivery data were retrieved from medical reports and the institutional database.

Results

The interobserver reliability for measuring levator hiatal dimensions between an experienced and inexperienced observer was substantial to almost perfect after a single 2.5-hour training session. For measuring the LUG, the interobserver reliability improved after a second training session, but it remained only fair to substantial. The interobserver reliability of diagnosing levator avulsions among five observers from four different centers varied widely. Both women who delivered vaginally and those who delivered by Cesarean section showed an increase in the distensibility of the levator hiatus during Valsalva maneuver compared with at 12 weeks’ gestation. Women with stress urinary incontinence (SUI) during pregnancy had a larger hiatal area compared with women without SUI. After childbirth, women with SUI had a more caudal and dorsal position of the bladder neck on Valsalva maneuver than women without SUI. Women who delivered by Cesarean section due to failure to progress had a smaller hiatal transverse diameter on pelvic floor contraction at 12 weeks’ gestation than women who had a spontaneous vaginal delivery. Women who had an instrumental vaginal delivery due to failure to progress showed a trend toward a smaller hiatal anteroposterior diameter on pelvic floor contraction at 36 weeks’ gestation than women who had a spontaneous vaginal delivery.

Conclusion

After adequate training, levator hiatal dimensions and the LUG can be reliably measured using 3D/4D transperineal ultrasound in women during and after their first pregnancy. Diagnosing levator avulsions in women 6 months after their first delivery is strongly observer-dependent. Women who delivered by Cesarean section showed an increase in the distensibility of the levator hiatus, which may imply that Cesarean section does not completely protect against changes in pelvic floor anatomy and function. SUI during first pregnancy is associated with a larger hiatal area. After childbirth, SUI is associated with a more caudal and dorsal position of the bladder neck on Valsalva maneuver. The sequence of these findings may indicate that the interaction between the levator ani muscle and endopelvic fascia is essential to maintain urethral support and urinary continence during and after first pregnancy. Smaller hiatal dimensions on pelvic floor contraction during first pregnancy are associated with an instrumental vaginal delivery or a Cesarean section due to failure to progress.