Objective To investigate the correlation of serum estradiol (E₂), relaxin (RLX) levels and pelvic floor ultrasound parameters with the severity of postpartum stress urinary incontinence (PSUI) in patients.

Methods A total of 144 patients with PSUI were enrolled in the PSUI group. According to the severity of the disease, they were divided into mild (n=59), moderate (n=55) and severe groups (n=30). Another 91 healthy postpartum women were selected as control group during the same period. General data of the PSUI group and the control group were compared. Serum E₂ and RLX levels in patients with different severity levels were analyzed. Pelvic floor ultrasound parameters among groups were compared. Multivariate Logistic regression analysis was used to screen the influencing factors for the occurrence of PSUI. The correlations of serum E₂, RLX levels and pelvic floor ultrasound parameters with the severity of PSUI were analyzed.

Results The serum RLX level in the PSUI group was significantly higher than that in the control group, while the E₂ level was significantly lower (P < 0.05). The serum E₂ level in the severe group was significantly lower than that in the moderate group and mild group, while the RLX level was significantly higher (P < 0.05). The proportions of multiple births, vaginal delivery, family history of urinary incontinence, mediolateral episiotomy and high serum RLX level as well as low serum E₂ level in the PSUI group were significantly higher than those in the control group (P < 0.05). In the mild group, moderate group and severe group, the bladder-urethral posterior angle (PUA), urethral tilt angle (UTA), levator hiatus area as well as Valsalva maneuver-related urethral rotation angle (URA), bladder neck descent (BND) at rest and during maximum Valsalva maneuver increased sequentially (P < 0.05). In the mild group, moderate group, and severe group, the bladder position (BDP) and bladder neck position (BNP) during Valsalva maneuver decreased sequentially (P < 0.05). The funnel formation rate of the internal urethral orifice in the PSUI group and the control group were 22.22% (32/144) and 6.59% (6/91), respectively. Multivariate Logistic regression analysis showed that parity, vaginal delivery, family history of urinary incontinence, mediolateral episiotomy and serum E₂ and RLX levels were influencing factors for the occurrence of PSUI (P < 0.05). Serum RLX levels and pelvic floor ultrasound parameters in PSUI patients were positively correlated with disease severity (r=0.573, 0.590, P < 0.05), while serum E₂ levels were negatively correlated with disease severity (r=-0.584, P < 0.001).

Conclusion Serum E₂ levels are negatively correlated with the severity of PSUI, while serum RLX levels and pelvic floor ultrasound parameters are positively correlated with the severity of PSUI. Parity, vaginal delivery, family history of urinary incontinence, mediolateral episiotomy and serum E₂ and RLX levels are influencing factors for the occurrence of PSUI.