During pregnancy, the strength of the pelvic floor muscles may decrease, which can lead to musculoskeletal changes that may facilitate the onset of urinary incontinence. The investigators decided to conduct this study firstly to analyze, through simple ultrasound indices, how the contractile capacity of the pelvic floor muscles affects postpartum urinary incontinence; secondly to study the correlation between the use of perineal gymnastics, the incidence of postpartum urinary incontinence, and the strength of floor contraction.