Second stage labour duration and pelvic floor outcomes in primiparous women delivering macrosomic foetuses: a prospective study.

BACKGROUND

To investigate the association between the duration of the second stage of labour (SSL) and early postpartum pelvic floor dysfunction (PFD) in primiparous women delivering macrosomic foetuses.

METHODS

200 eligible primiparous women were stratified by SSL duration into Group A (t ≥ 3h), Group B (2h ≤ t < 3h), and Group C (t < 2h). At six weeks postpartum, transperineal ultrasound was performed to determine bladder neck position and levator ani hiatus (LAH) area. Pelvic floor muscle (PFM) strength was evaluated using the Oxford scale, while PFM function was measured via vaginal pressure testing. The occurrences of stress urinary incontinence (SUI) and pelvic organ prolapse (POP) were recorded.

RESULTS

The incidence of POP was significantly higher in Group A (23.33%) compared with Group B (6.67%) and C (5%) (P < 0.05). Weak PFM strength was observed in 56.67% of women in Group A versus 21.67% and 21.25% in Groups B and C, respectively (P < 0.05). Vaginal pressure in Group A (class I fibres: 61.38 ± 4.97; class II fibres: 80.63 ± 3.18) was markedly lower than in Group B (I: 78.35 ± 5.08; II: 93.73 ± 4.39) and C (I: 76.55 ± 4.49; II: 92.10 ± 4.40) (P < 0.001). Muscle fatigue was notably higher in Group A (I: 8.65 ± 0.95; II: 3.98 ± 0.65) compared with Group B (I: 4.78 ± 0.61; II: 2.28 ± 0.49) and C (I: 4.25 ± 0.56; II: 2.53 ± 0.55) (P < 0.001). LAH area during Valsalva was significantly larger in Group A (25.48 ± 3.77) than in Groups B (18.55 ± 2.87) and C (17.68 ± 2.72) (P < 0.001), with corresponding LAH expansion rate of 75%, 40%, and 43.75% (P < 0.05).

CONCLUSION

A prolonged SSL (≥ 3 h) is associated with weaker PFM strength, greater muscle fatigue, enlarged levator hiatus, and a higher incidence of POP in primiparous women delivering macrosomic foetuses.