Abstract:Objective To evaluate the effect of different delivery methods on pelvic floor function in women of advanced maternal age by transvaginal four-dimensional ultrasound. Methods The clinical data of 300 women (aged ≥ 35 years old), admitted to Tangshan Maternal and Child Health Hospital from December 2017 to December 2020 were retrospectively analyzed. According to the mode of delivery, the women were divided into spontaneous delivery group (n=150) and cesarean section group (n=150). The puerperas were examined by transvaginal four-dimensional ultrasound on the 49th day after delivery to analyze the effect of different delivery modes on pelvic floor function in two groups. Results During anal sphincter contraction, the urethra rotation angle and bladder neck mobility in cesarean section group were significantly higher than spontaneous delivery group (P＜0.05). Under resting conditions, there was no significant difference in the distance from cervical mouth position (CMP) to pubic symphysis, the distance from bladder neck position (BNP) to pubic symphysis, the posterior urethra-vesical angle (PUA), urethra tilt angle (UTA) and anal muscle clamp angle (levator ani muscles angle) between two groups (P＞0.05). Under the maximum Valsalva motion, the distances between CMP and pubic symphysis and between BNP and pubic symphysis in cesarean section group were significantly smaller than those in delivery group (P＜0.05), and PUA, UTA and anal muscle clamp angle were significantly lower than those in delivery group (P＜0.05). Conclusion Transvaginal four-dimensional ultrasound shows little effect on the pelvic floor function of older pregnant women and can determine the degree of pelvic floor disorders. With a low-cost and simple method, four-dimensional ultrasound can be used repeatedly for early diagnosis and intervention of pelvic floor functional diseases in women of advanced maternal age.