2D pelvic floor ultrasound imaging in identifying levator ani muscle trauma agrees highly with 4D ultrasound imaging

Introduction and hypothesis The objective was to evaluate the agreement between 2D and 4D translabial ultrasound (TLUS) technique in showing levator ani muscle (LAM) states after vaginal birth. Methods In a prospective observational cohort study between March 2017 and April 2019 we evaluated LAM states (intact, hematoma, partial, complete avulsion) of primiparous women having given birth vaginally with singletons in vertex presentation ≥ 36+0 gestational weeks by using 2D and 4D TLUS within 1–4 days postpartum (assessment A1) and again 6–10 weeks postpartum (assessment A2). Cohen’s Kappa analysis was performed for each side separately to evaluate the test agreement between the two ultrasound techniques at every assessment period. Results A total of 224 women participated at A1 and 213 at A2. The agreement between the two ultrasound techniques was good to very good at A1 (Cohen`s kappa right-sided 0.78, left-sided 0.82) and very good at A2 (Cohen`s kappa both sides 0.88). The agreement was best when assessing an intact LAM or a complete avulsion (Cohen`s kappa between 0.78–0.92 for complete avulsions). Conclusions The comparison between 2D and 4D TLUS showed a good to very good agreement in LAM trauma immediately after birth as well as 6–10 weeks postpartum. Therefore, 2D ultrasound could also be a valuable method for demonstrating a LAM abnormality and could be used in settings where 3D/4D ultrasound equipment is not available.