Ultrasonic Analysis of Maternal Pelvic Floor Differences Among Delivery Mode Combinations After the Second Birth: A Single-Center Study.

Purpose: This study aimed to assess the impact of delivery mode combinations after the second birth on maternal pelvic floor differences using transperineal ultrasound.

Methods: A total of 266 women were enrolled in this study. According to the different delivery modes of two births, women were categorized as repeat vaginal birth (RVB), vaginal birth after cesarean section (VBAC), cesarean section after vaginal birth (CAVB), and repeat cesarean section (RCS) groups. Univariate analysis was performed to compare levator hiatus area (LHA-V), bladder neck-symphyseal distance on Valsalva (BSD-V), bladder neck descent (BND), and the occurrence of pelvic organ prolapse (POP) among the four groups. Multiple linear regression analysis was performed to identify factors associated with LHA-V.

Results: BSD-V in the RVB, VBAC and CAVB groups was lower and their BND was greater than the counterparts in the RCS group (p < 0.05). The VBAC group exhibited a significantly lower BSD-V and greater BND compared to the CAVB group. The prevalence of POP was the highest in the RVB group and the lowest in the RCS group. LHA-V was the only ultrasound parameter statistically different in all pairwise comparisons among the four groups. The multiple linear regression analysis results demonstrated a significant relationship between LHA-V and different delivery modes of two births, neonatal weight, BND, uterine and perineal body position on Valsalva.

Conclusion: For women with both modes, vaginal birth after cesarean section exhibited significantly lower BSD-V, greater BND and larger LHA-V, with a higher prevalence of POP compared to the reverse sequence. Meanwhile, LHA-V was identified as a sensitive ultrasound indicator for differentiating pelvic floor outcomes across delivery mode combinations.