1 in 5 women experience an injury to the levator ani muscles (LAM) during their first vaginal delivery. Certain obstetric factors increase the risk of LAM trauma. The severity of LAM deficiency is linked to pelvic floor weakness, which serves as a risk factor for pelvic floor disorders. To investigate the relationship between pelvic floor strength and pelvic floor dysfunction following the first vaginal delivery in low-risk compared to high-risk obstetric cohort.

This prospective, single-site cohort study involved primiparous females from 2012 to 2020. High-risk women had a second-degree or greater perineal laceration, prolonged second-stage labor (>160 min), instrumented delivery, or fetal head circumference >35.5cm. Low-risk women did not have such risk factors. Obstetric data were collected through chart review. At the 6-week postpartum visit, pelvic organ prolapse was assessed, and levator ani strength was measured using the Peritron perineometer, using 20cmH20 as a cut off for moderate to high strength. At 12 weeks postpartum, patients completed PFIQ-20 and PGDI-7 questionnaires.

There were 127 patients total 59 patients (46%) were low-risk and 68 (54%) were high-risk. Median age of the high-risk group was 26 and low-risk group was 23. The majority of participates were Caucasian. The mean vaginal strength was 20.3 cmH2O (SD 11.7) in the low-risk group and 20.4 cmH2O (SD 12.5) in the high-risk group (p=0.95). There was no difference in the PFIQ-7 and PFDI-20 summary scores when comparing low and high vaginal strength (p=0.46, p=0.67). When vaginal strength was stratified by low versus high-risk groups, there was no significant differences in PFIQ-7 or PFDI-20 scores (all p-values > 0.5).

There is not overall association between pelvic floor strength and pelvic dysfunction during the postpartum period, whether assessed in low or high-risk obstetric groups. Additionally, current evidence does not support using pelvic floor strength at 6 weeks postpartum as a reliable predictors of pelvic floor dysfunction symptoms at 12 weeks in either low or high-risk obstetric populations.