Pelvic Floor Strength and Dysfunction in a Low vs High-risk Obstetric Population

Objectives: Twenty percent of women will have a levator ani muscle (LAM) injury during their first vaginal delivery. Obstetric factors that are associated with an increased risk for LAM trauma include large fetal head circumference, forceps assisted vaginal delivery, prolonged second stage of labor. In turn, LAM deficiency severity is associated with clinically significant prolapse. Pelvic floor weakness occurs following childbirth, which then is a risk factor for the development of pelvic floor disorders. To date, no studies have compared the association between pelvic floor strength and postpartum pelvic dysfunction when comparing high and low-risk obstetric populations. The objective of this study is to examine the association between pelvic floor strength and pelvic floor dysfunction after the first vaginal delivery in low-risk versus high-risk obstetric population.

Methods: This was a single-site cohort study of patients undergoing their first vaginal delivery who were recruited between the years 2012 and 2020 at a large university hospital’s Obstetric and Gynecology Department. Subjects were categorized as high risk if they had a second degree or greater perineal laceration or any previously defined risk factors for LA injury at vaginal birth (including prolonged second stage of labor >160 min, instrumented delivery, or fetal head circumference >35.5cm). Women were classified as low risk if they had an intact perineum and no previously defined risk factors for LAM injury at vaginal birth.
Relevant obstetric information was obtained by chart abstraction. At the 6-week postpartum visit, a history was obtained, and an exam was performed using the pelvic organ prolapse quantification system. Levator ani strength was measured using the Peritron™ perineometer. Vaginal closure force (in cmH20) was measured at both rest and during maximal voluntary contraction. Patients also completed PFIQ-20 and PFDI-7 questionnaires at 12 weeks postpartum. The Chi-squared tests, t-tests and Wilcoxon rank sum tests were used to analyze data.

Results: Of the 160 patients that were consented for the study, a total of 127 had complete data sets with completed survey questionnaires. Of the studied population, 59 patients (46%) were low risk and 68 (54%) were high risk. The mean vaginal strength was 20.3 (SD 11.7) cmH2O in the low-risk group and 20.4 (SD 12.5) cmH2O 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 obstetric groups, there was no significant differences in PFDI-20 or PFIQ scores (all p-values >0.5).

Conclusions: In the postpartum period, there is no association between pelvic floor strength and pelvic dysfunction overall or when stratified by low versus high-risk obstetric groups.