Application of Transperineal 3‐Dimensional Ultrasound in Evaluating Levator Ani Muscle Contraction During Female Pelvic Floor Rehabilitation

Abstract

Objectives

Pelvic floor disorders (PFD) and functional alterations are common among women and may affect quality of life. This study aimed to observe levator ani muscle (LAM) contraction by transperineal 3‐dimensional ultrasound and to explore the relationship between ultrasound‐derived pelvic floor muscle strength evaluation during contraction and clinical Oxford grading.

Methods

A total of 954 postpartum patients receiving pelvic floor rehabilitation at Xiamen Humanity Maternity Hospital from October 2022 to January 2025 were enrolled. Patients were categorized according to clinical Oxford muscle strength grade, and all underwent transperineal pelvic floor ultrasound. The ultrasound‐derived relative strain parameters of the LAM—specifically, changes in hiatal area, muscle length, and anteroposterior diameter during contraction—were measured to evaluate the agreement between ultrasound assessment and clinical Oxford grading.

Results

A significant correlation was found between ultrasound‐based assessments and clinical Oxford grading (p < .001). The change in LAM anteroposterior diameter during contraction showed the highest correlation with Oxford grade (ρ = 0.809), followed closely by changes in hiatal area and muscle length (ρ = 0.771 and ρ = 0.781, respectively).

Conclusion

Transperineal 3‐dimensional ultrasonography allows non‐invasive and quantitative evaluation of pelvic floor anatomy. The strong correlations between dynamic parameters and the Oxford score demonstrate its ability to objectively assess pelvic floor muscle strength. This modality may therefore contribute to the objective characterization of pelvic floor muscle function and may inform future studies in postpartum pelvic floor rehabilitation.

Abbreviations

AP

anteroposterior

LAM

levator ani muscle

PFD

pelvic floor disorder

POP

pelvic organ prolapse

SD

standard deviation

SUI

stress urinary incontinence

Pelvic floor disorders (PFD) and functional alterations are common among women, particularly during pregnancy and the postpartum period. The growing bulk and volume of the uterus during pregnancy exert considerable stress on pelvic floor tissues, making women susceptible to PFD. The levator ani muscle (LAM) is a 3‐dimensional structure that inclines anteromedially and comprises the puborectalis, iliococcygeus, and pubococcygeus muscles. Voluntary and reflex contractions of the levator ani can reduce the size of the levator hiatus, thereby counteracting sudden increases in intra‐abdominal pressure and stabilizing the pelvic organs. Postpartum, the LAM frequently experiences varying degrees of morphological and functional alterations, which may endure and adversely impact women's quality of life, potentially resulting in stress urinary incontinence (SUI), pelvic organ prolapse (POP), and pelvic pain. ¹ Multiple population‐based surveys worldwide have shown that, in the general female population, the prevalence of SUI ranges from 10 to 40%, while POP has been reported in 9.7 to 49.7% of women. ² It should be acknowledged that POP is a multifactorial condition. Structural factors, such as levator ani trauma and connective tissue integrity, have been shown to be more strongly associated with prolapse severity than pelvic floor muscle strength alone, and no consistent association between POP‐Q stage and measured muscle strength has been demonstrated. However, previous studies have reported weak or inconsistent associations between pelvic floor muscle strength and SUI, suggesting that neuromuscular timing, reflex activity, coordination, and connective tissue support may also play important roles.

This study aims to evaluate the accuracy of transperineal 3‐dimensional ultrasonography in the objective assessment of pelvic floor muscle strength. In this study, LAM strain parameters examined their connection with clinical Oxford grading. These findings may offer imaging‐based evidence to support the development of individualized pelvic floor rehabilitation strategies.

Methods

Subjects

This was a prospective study. Patients who underwent postpartum pelvic floor rehabilitation at Xiamen Humanity Maternity Hospital between October 2022 and January 2025 were included. Inclusion criteria were: (1) primiparous women, the pre‐pregnancy BMI was in the standard range; (2) age 20–40 years without serious pregnancy complications or comorbidities; (3) pelvic floor re‐evaluation 42 days to 6 months postpartum including Oxford muscle strength grading (0–5) and transperineal 3D ultrasound; (4) full cooperation with all examinations. Exclusion criteria included: (1) inability to complete examination or other postpartum illness; (2) history of LAM or anal sphincter rupture, neurological disorders, pelvic masses, or genitourinary infections; (3) congenital pelvic floor abnormalities or prior POP; (4) forceps/vacuum use. Ethical approval was obtained from the Ethics Committee of Xiamen Humanity Hospital (approval no. HAXM‐MEC‐20221010‐039‐02). The study complied with the ethical principles of the Declaration of Helsinki and received exemption from signed informed consent. Participant privacy and data confidentiality were strictly protected throughout the study.

Oxford Grading System ³

The modified Oxford grading system was used to evaluate pelvic floor muscle strength: Grade 0: no contraction detected by the examiner; Grade 1: muscle flicker or pulsation felt by the examiner's finger; Grade 2: weak contraction with increased muscle tone but no noticeable lift; Grade 3: moderate contraction characterized by lifting of the posterior vaginal wall and squeezing felt at the examiner's finger base, with inward movement of the perineal body; Grade 4: good contraction strong enough to lift the vaginal wall against resistance and compress 2 fingers; Grade 5: strong contraction with firm compression of the examiner's fingers against each other. Oxford muscle strength grading was independently performed by 2 obstetricians with more than 5 years of clinical experience in pelvic floor rehabilitation. Prior to data collection, all examiners underwent structured training specific to this study, including theoretical review of the Modified Oxford Scale, video‐based case analysis, and supervised hands‐on practice sessions. A standardized assessment protocol was implemented to minimize inter‐observer variability. Previous studies have shown that structured training improves agreement in Modified Oxford Scale scoring. Formal inter‐rater reliability statistics were not calculated in the present study. During examination, participants were placed in the lithotomy position. The examiner wore sterile gloves and applied water‐based lubricant to the index and middle fingers. Two fingers were gently inserted into the vagina with the finger pads oriented posteriorly and positioned at the mid‐vaginal level to palpate the medial border of the pelvic floor muscles, primarily corresponding to the puborectalis portion of the levator ani. Participants were given standardized verbal instructions: “Please contract your pelvic floor muscles as if trying to stop urine or gas, squeeze inward and lift upward as strongly as possible, and avoid using abdominal or gluteal muscles.” The examiner assessed contraction strength, duration, vaginal wall elevation, and compression against the fingers to determine the Oxford grade (0–5). Each assessment was repeated 3 times, and the mean value was recorded.

Ultrasound Parameter Measurement and Calculation

A GE Voluson E8 color Doppler ultrasound diagnostic system (GE Healthcare, USA) equipped with an abdominal 3‐dimensional volumetric probe (frequency: 4–8 MHz) was utilized. Participants were instructed to empty their bladder and rectum and were placed in the lithotomy position. The probe was covered with a sterile isolation membrane and coated with sterile coupling gel before being positioned on the perineum. Imaging was standardized by ensuring that the pubic symphysis, urethra, vagina, and rectal ampulla were clearly visualized in the midsagittal plane. The 4‐dimensional (dynamic 3‐dimensional) scanning program was initiated while participants were at rest, then maximal anal contraction was performed and maintained until image acquisition was completed. All ultrasound images were stored in the Voluson E8 system. Three trained sonographers independently measured the levator hiatus area, the length of the medial border of the LAM, and the anteroposterior diameter at both rest and maximal contraction, using the plane with the minimal levator hiatus. During assessment, visible or palpable activation of accessory muscles, including the abdominal, gluteal, or hip adductor muscles, was monitored to ensure correct pelvic floor muscle contraction. All operators received standardized training and followed a unified measurement protocol to minimize inter‐observer variability. Pelvic floor ultrasound examinations were completely blinded to the Oxford grading results and all clinical examination information. All 3D transperineal ultrasound volumes were acquired during the clinical encounter and measured offline on a dedicated workstation by blinded sonographers. As shown in Figure 1, the 2 examiner teams worked independently to minimize observer bias.

Figure 1.

Three‐dimensional transperineal ultrasound image of the female levator hiatus. A, Resting state; B, squeeze state; A, hiatal area; L, LAM length; D, anteroposterior diameter.

Specifically:

The term “LAM strain parameters” refers to the relative magnitude of morphological change in hiatal area, muscle length, and anteroposterior diameter between rest and maximal voluntary contraction, as quantified by transperineal 3‐dimensional ultrasound.

Change in LAM Hiatal Area during Contraction:

ΔS = (S1 − S2)/S1, where S1 is the hiatal area at rest and S2 is the hiatal area during contraction.

Change in LAM Length during Contraction:

ΔM = (M1 − M2)/M1, where M1 is LAM length at rest and M2 is the length during contraction.

Change in LAM Anteroposterior Diameter during Contraction:

ΔL = (L1 − L2)/L1, where L1 is the anteroposterior diameter at rest and L2 is the diameter during contraction.

Each participant was instructed to perform 3 maximal voluntary pelvic floor muscle contractions. All ultrasound measurements were obtained during each contraction, and the average value of the 3 attempts was used for statistical analysis. Two senior physicians independently conducted single‐blinded evaluations.

Statistical Analysis

All data analyses were conducted using R software (Version 4.3.2). Continuous variables were expressed as mean ± standard deviation ($\overline{x}$±SD) and compared between groups using t‐tests. Variables with a normal distribution were expressed as mean ± standard deviation (SD), whereas non‐normally distributed data were reported as median (Q₁, Q₃). Comparisons among multiple groups were conducted using 1‐way ANOVA or Kruskal–Wallis test, depending on the distribution of the data. Categorical variables were presented as n (%) and compared using the chi‐square test or Fisher's exact test, as appropriate. Spearman rank correlation analysis and linear regression were used to evaluate the relationship between ultrasound‐measured changes and clinical Oxford grades. p Value <.05 was considered statistically significant.

Results

For clarity, S1 and S2 represent the levator hiatus area at rest and during maximal voluntary contraction, respectively; M1 and M2 denote LAM length at rest and during contraction; and L1 and L2 refer to the anteroposterior diameter at rest and during contraction. The symbols ΔS, ΔM, and ΔL indicate the relative magnitude of change between rest and contraction.

Baseline Characteristics and Measurement Differences

Based on the Modified Oxford Scale grading, 31 participants (3.2%) were classified as grade 0, 407 (42.7%) as grade 1, 298 (31.2%) as grade 2, 182 (19.1%) as grade 3, and 36 (3.8%) as grade 4. None of the participants were classified as grade 5 in Oxford muscle strength. A total of 859 women had vaginal deliveries and 95 underwent cesarean sections. The proportion of participants with higher pelvic floor muscle strength (defined as Oxford grade ≥3) was lower in the vaginal delivery group compared to the cesarean section group. Ultrasound measurements of the LAM during contraction showed that as the Oxford grade increased, the magnitude of changes in hiatal area, muscle length, and anteroposterior diameter also increased. S1 differed across groups (median 13.18 [IQR 11.51–14.91] overall). S2 also differed (median 10.43 [9.14–11.88] overall). ΔS differed (median 0.19 [0.13–0.26] overall). M1 differed (median 8.41 [7.69–9.18] overall). M2 differed (median 7.03 [6.39–7.74] overall). ΔM differed (median 0.16 [0.11–0.21] overall). L1 differed (median 4.76 [4.38–5.16] overall). L2 differed (median 3.93 [3.56–4.31] overall). ΔL differed (median 0.16 [0.11–0.22] overall). The intergroup comparisons showed statistically significant differences (p < .001). No statistically significant differences were observed in Birth (p = .506) or Parity (p = .651) distributions across the groups (see Table 1).

Table 1.

Comparison of Ultrasound Parameters Across Oxford Grading Groups

Variables	Total (n = 954)	0 (n = 31)	1 (n = 407)	2 (n = 298)	3 (n = 182)	4 (n = 36)	Statistic	p
S1, M (Q₁, Q₃)	13.18 (11.51, 14.91)	13.96 (11.97, 15.23)	12.82 (11.18, 14.32)	13.00 (11.54, 14.91)	13.76 (12.06, 15.25)	14.83 (13.56, 16.27)	χ2 = 33.81 a	<.001
S2, M (Q₁, Q₃)	10.43 (9.14, 11.88)	13.13 (11.62, 14.93)	10.87 (9.73, 12.41)	10.36 (9.12, 11.50)	9.57 (8.50, 10.94)	8.98 (8.32, 10.42)	χ2 = 102.14 a	<.001
ΔS, M (Q₁, Q₃)	0.19 (0.13, 0.26)	0.02 (0.01, 0.04)	0.14 (0.10, 0.18)	0.23 (0.17, 0.28)	0.30 (0.23, 0.35)	0.39 (0.33, 0.45)	χ2 = 543.76 a	<.001
M1, M (Q₁, Q₃)	8.41 (7.69, 9.18)	8.57 (7.91, 9.52)	8.31 (7.55, 9.03)	8.45 (7.65, 9.11)	8.59 (7.91, 9.29)	9.14 (8.28, 9.89)	χ2 = 18.93 a	<.001
M2, M (Q₁, Q₃)	7.03 (6.39, 7.74)	8.42 (7.70, 9.34)	7.39 (6.61, 8.00)	6.94 (6.34, 7.55)	6.59 (6.01, 7.19)	6.26 (5.61, 6.99)	χ2 = 124.16 a	<.001
ΔM, M (Q₁, Q₃)	0.16 (0.11, 0.21)	0.02 (0.01, 0.04)	0.12 (0.09, 0.15)	0.18 (0.14, 0.21)	0.23 (0.20, 0.26)	0.31 (0.28, 0.34)	χ2 = 550.92 a	<.001
L1, M (Q₁, Q₃)	4.76 (4.38, 5.16)	4.72 (4.45, 5.12)	4.62 (4.31, 5.09)	4.80 (4.41, 5.13)	4.86 (4.49, 5.23)	5.05 (4.74, 5.38)	χ2 = 21.41 a	<.001
L2, M (Q₁, Q₃)	3.93 (3.56, 4.31)	4.65 (4.24, 4.92)	4.11 (3.76, 4.49)	3.91 (3.55, 4.23)	3.62 (3.38, 3.96)	3.38 (3.04, 3.80)	χ2 = 151.48 a	<.001
ΔL, M (Q₁, Q₃)	0.16 (0.11, 0.22)	0.04 (0.02, 0.05)	0.12 (0.09, 0.15)	0.19 (0.15, 0.22)	0.25 (0.22, 0.28)	0.33 (0.28, 0.37)	χ2 = 600.36 a	<.001
Birth, n (%)							χ2 = 3.32	0.506
1	859 (90.04)	27 (87.10)	372 (91.40)	270 (90.60)	159 (87.36)	31 (86.11)
2	95 (9.96)	4 (12.90)	35 (8.60)	28 (9.40)	23 (12.64)	5 (13.89)
Parity, n (%)							—	.651 b
1	479 (50.21)	13 (41.94)	212 (52.09)	150 (50.34)	89 (48.90)	15 (41.67)
2	394 (41.30)	14 (45.16)	165 (40.54)	126 (42.28)	72 (39.56)	17 (47.22)
3	75 (7.86)	4 (12.90)	26 (6.39)	21 (7.05)	20 (10.99)	4 (11.11)
4	4 (0.42)	0 (0.00)	3 (0.74)	0 (0.00)	1 (0.55)	0 (0.00)
5	2 (0.21)	0 (0.00)	1 (0.25)	1 (0.34)	0 (0.00)	0 (0.00)

χ², chi‐square test; —, Fisher exact; M, median; Q₁, 1st quartile; Q₃, 3rd quartile.

^a Kruskal–Wallis test.

^b Simulated p‐value.

Correlation Analysis

Correlation analysis was conducted between Oxford grading and LAM strain parameters during contraction, including changes in hiatal area, LAM length, and anteroposterior diameter. Results showed that Oxford grade was positively correlated with hiatal area change (ρ (95% CI) = 0.771 (0.744–0.796), p < .001)(Figure 2), LAM length change (ρ (95% CI) = 0.781 (0.755–0.805), p < .001) (Figure 3), and anteroposterior diameter change (ρ (95% CI) = 0.809 (0.786–0.830), p < .001) (Figure 4). The strongest correlation was found with the anteroposterior diameter change (ρ = 0.809), although the correlation coefficients among all 3 parameters were relatively close (0.771–0.781). The strongest correlation was found for ΔL, suggesting that relative morphological changes during contraction may more strongly reflect functional muscle strength. These findings indicate that ultrasound‐based measurements reliably reflect differences in muscle strength grading and support the potential utility of this method.

Figure 2.

Correlation between LAM hiatal area change during contraction and clinical Oxford grading of pelvic floor muscle strength.

Figure 3.

Correlation between LAM length change during voluntary contraction and clinical Oxford grading of pelvic floor muscle strength.

Figure 4.

Correlation between LAM anteroposterior diameter of the levator hiatus change during voluntary contraction and clinical Oxford grading of pelvic floor muscle strength.

Linear Regression

Univariate regression analysis demonstrated that all resting and contraction parameters (S1, S2, M1, M2, L1, and L2) as well as their relative changes (ΔS, ΔM, and ΔL) were significantly associated with the outcome variable (all p < .001). However, in the multivariate model, only ΔS (β = 2.11, 95% CI: 0.01–4.21, p = .049) and ΔM (β = 4.94, 95% CI: 1.28–8.59, p = .008) remained significant independent predictors. The change in anteroposterior diameter (ΔL) showed a trend toward significance (β = 3.60, 95% CI: −0.03–7.22, p = .052), suggesting a potential but inconclusive association. No significant effects were observed for S1, S2, M1, M2, L1, or L2 in the adjusted model (see Table 2).

Table 2.

Univariate and Multivariate Linear Regression Analyses of Ultrasound Parameters Associated with the Oxford Grading

Variables	Univariate					Multivariate
	β	S.E	t	p	β (95% CI)	β	S.E	t	p	β (95% CI)
S1	0.06	0.01	5.39	<.001	0.06 (0.04 ~ 0.08)	0.05	0.06	0.81	.417	0.05 (−0.07 ~ 0.17)
S2	−0.14	0.01	−10.69	<.001	−0.14 (−0.17 ~ −0.12)	−0.03	0.08	−0.40	.690	−0.03 (−0.18 ~ 0.12)
△S	7.38	0.20	37.36	<.001	7.38 (7.00 ~ 7.77)	2.11	1.07	1.97	.049	2.11 (0.01 ~ 4.21)
M1	0.10	0.03	3.82	<.001	0.10 (0.05 ~ 0.15)	−0.15	0.18	−0.83	.408	−0.15 (−0.51 ~ 0.21)
M2	−0.30	0.03	−11.48	<.001	−0.30 (−0.35 ~ −0.25)	0.13	0.22	0.58	.563	0.13 (−0.30 ~ 0.55)
△M	9.82	0.25	38.59	<.001	9.82 (9.33 ~ 10.32)	4.94	1.87	2.65	.008	4.94 (1.28 ~ 8.59)
L1	0.15	0.04	3.60	<.001	0.15 (0.07 ~ 0.23)	0.10	0.31	0.33	.743	0.10 (−0.51 ~ 0.71)
L2	−0.51	0.04	−12.01	<.001	−0.51 (−0.60 ~ −0.43)	−0.16	0.37	−0.43	.664	−0.16 (−0.88 ~ 0.56)
△L	9.74	0.23	42.44	<.001	9.74 (9.29 ~ 10.19)	3.60	1.85	1.94	.052	3.60 (−0.03 ~ 7.22)

CI, confidence interval.

Discussion

This study evaluated pelvic floor muscle strength using transperineal ultrasound by quantifying relative changes in levator ani hiatal dimensions, including hiatal area, length, and anteroposterior (AP) diameter. Among 954 women, the magnitude of change in hiatal area, muscle length, and anteroposterior diameter increased progressively with higher Oxford grades, and all demonstrated strong positive correlations with clinical muscle strength. The AP diameter change demonstrated the highest correlation (ρ = 0.809) with clinical muscle strength. These findings indicate that ultrasound‐based measures of hiatal dynamics reflect clinically meaningful differences in pelvic floor muscle strength.

The use of ultrasound to assess levator ani function is well supported by prior research. Foundational work by Dietz and colleagues first described the morphological characteristics of the levator hiatus and demonstrated the relationship between hiatal distension and pelvic floor loading. ¹ , ⁴ , ⁵ Subsequent studies confirmed that hiatal configuration during contraction is directly influenced by LAM performance. Systematic reviews ⁶ , ⁷ , ⁸ have further validated the reproducibility and functional relevance of ultrasound‐derived hiatal measurements, highlighting moderate‐to‐strong correlations with clinical pelvic floor assessments. Our findings are consistent with these established observations, particularly regarding the responsiveness of the AP diameter, which reflects the primary axis of levator shortening during contraction and can be obtained even with basic 2D equipment.

In this cohort, the pattern of increasing dynamic deformation (larger strain values) with higher Oxford grades supports the concept that functional contraction results in measurable narrowing of the levator hiatus. The lack of Oxford grade 5 cases and the predominance of grades 1–2 reflect typical postpartum distributions observed in previous population‐based studies. ⁷ Because women with morphological abnormalities such as levator avulsion or anal sphincter injury were excluded, the observed differences represent functional variation in muscle recruitment rather than structural defects. The multivariable analysis further demonstrated that changes in hiatal area and length independently predicted muscle strength, indicating that multiple dimensions of hiatus deformation contribute meaningful information to functional assessment.

Although the Oxford grading system is widely used in clinical practice, its subjectivity and limited reproducibility hinder accurate and consistent evaluation of pelvic floor muscle strength. In contrast, transperineal 3D ultrasound is a noninvasive, reproducible, and quantitative imaging technique. It enables clear visualization of pelvic structures while avoiding interference from bones, bowel contents, or the abdominal wall. ⁹ , ¹⁰ Previous studies have confirmed a strong association between pelvic floor muscle function and changes in pelvic anatomy, supporting the use of ultrasound in functional assessments. ¹¹ , ¹² Multiple studies have demonstrated the value of various ultrasound techniques in the visualization of pelvic floor structures and the diagnosis of related injuries. The reported correlation between these ultrasound findings and the Oxford grading scale of pelvic floor muscle strength ranges from 0.37 to 0.77. ⁵ Majida et al ¹³ reported good interobserver reliability (ICC 0.61–0.96) in measuring pelvic floor anatomy and function at rest and during contraction using 3D/4D transperineal ultrasound. However, only 29% of cases yielded usable results during Valsalva maneuvers due to technical limitations. Valsky's review ⁷ highlighted that 3D transperineal ultrasound offers clear visualization of both anterior and posterior pelvic compartments, though large‐scale studies are needed to confirm its clinical utility. Research by Dietz ⁴ , ⁸ further indicated a moderate correlation between bladder neck mobility measured via ultrasound and Oxford grading (ρ = 0.62), and emphasized the advantages of ultrasound in multidisciplinary management of PFD due to its real‐time capability, high resolution, and low cost. Zhang et al ⁶ compared 3D ultrasound with conventional methods and found superior accuracy (94.4% versus 80.6%) and sensitivity (92.6% versus 77.8%) in postpartum pelvic floor assessment, recommending its widespread adoption.

This study has several strengths. It includes a large sample size, employs blinded ultrasound assessment, and uses dynamic measurements rather than static dimensions alone. Nonetheless, limitations must be acknowledged. All measurements were performed in the lithotomy position, which may not fully reflect functional loading conditions encountered in upright posture. The cross‐sectional design precludes inference of causality, and the relatively small number of high‐strength (Oxford 4–5) cases may limit the precision of estimates across the upper range of muscle strength. Future studies should incorporate upright assessments and longitudinal follow‐up to evaluate whether dynamic hiatal measurements predict functional recovery or symptom development.

Recent imaging studies have emphasized the value of transperineal ultrasound for characterizing levator ani function in the postpartum population. ¹⁴ , ¹⁵ Foundational work has shown that hiatal dimensions and their dynamic changes during contraction reflect levator ani recruitment rather than structural pathology, particularly when women with avulsion or sphincter injury are excluded. ¹ , ⁷ , ¹³ Our findings are consistent with this functional perspective, demonstrating that greater narrowing of the hiatus during voluntary contraction is associated with higher clinical muscle strength. The strong responsiveness of the AP diameter observed in this study aligns with prior evidence highlighting this axis as the primary direction of levator ani shortening. ⁸ Dynamic ultrasound assessment therefore provides additional objective information beyond static imaging and offers a useful complement to clinical palpation for evaluating pelvic floor muscle performance.

In summary, transperineal ultrasound provides reproducible, quantitative markers of pelvic floor muscle strength. Dynamic changes in hiatal dimensions—particularly the AP diameter—correlate strongly with Oxford grading and may offer a useful adjunct to clinical evaluation in postpartum pelvic floor assessment.

Conclusion

This study demonstrated that transperineal 3‐dimensional ultrasound enables accurate assessment of pelvic floor muscle function and quantification of LAM strain parameters, which showed strong correlations with Oxford grading. Objective evaluation of pelvic floor strength using LAM strain parameters provides quantitative and reproducible indicators for characterizing pelvic floor muscle function. These parameters may provide a quantitative reference for future longitudinal studies evaluating changes in pelvic floor muscle function following intervention and may assist clinicians in postpartum pelvic floor assessment.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.