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Effect of different delivery modes on pelvic floor structure revealed by ultrasonography

Qian Wang1, Li Wang2 and Qiang Li3*

1Department of Ultrasound, Liaocheng People’s Hospital, Liaocheng, P. R. China

2Department of Science and Education, Liaocheng People’s Hospital, Liaocheng, P. R. China

3Department of Anorectal, Liaocheng People’s Hospital, Liaocheng, P. R. China

*Corresponding Author:
Qiang Li
Department of Anorectal
Liaocheng People’s Hospital
Liaocheng, P. R. China

Accepted date: August 07, 2017

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Objective: This study is to investigate the effect of different delivery modes on pelvic floor structure by using ultrasonography.

Method: A total of 194 cases of patients visited Liaocheng Peoples’ Hospital aged between 25 to 40 y old were enrolled in this retrospective study. According to their fertility status, these 194 cases were divided into childless group and fertility group. The fertility group was divided into vaginal delivery group and cesarean section group according to the delivery modes. GE E8 cavity was used to detect relative distances (bladder neck-symphyseal short, BSD; bladder neck descent, BND; detrusor thickness, DT) and angles (bladder urethra after angle, bladder neck rotation angle) of each group in different states. We compare the differences between groups by corresponding statistical methods.

Results: There was no significant difference in BSD, DT and posterior vesicourethral angle (β) between childless and fertility groups under the resting states, while β was different between vaginal delivery and cesarean delivery groups. During Valsalva movement, BND, β, and bladder neck rotation angle were different between each groups, and the differences were statistically significant. The stress urinary incontinence diagnosis rate of fertility group was statistically higher than that of childless group, and so did the vaginal delivery and cesarean delivery.

Conclusion: Pregnancy and delivery can damage the pelvic floor system, and the pelvic anatomy changes caused by delivery might play a key role in the postpartum stress urinary incontinence. These results can provide the useful information to establish the meaningful guidelines to assist both patients and health care providers in making decision.


Pelvic ultrasound, Delivery mode, Pelvic floor functional disorder


Female pelvic floor, which is close to the pelvic outlet, iscomposed of multiple layers of muscle, fascia and ligament. Itconstitutes a complex pelvic support system and pelvic floorfunction is a dynamic equilibrium system that relies on theinteraction of intact muscle, knotted tissue and nervedistribution [1]. If it is damaged in any of the bones, muscles,or nerves of three compartment levels of the pelvic floor, theremay cause Pelvic Floor Dysfunction (PFD). Currently, PFD isone of the most common chronic diseases affecting women’sphysical and mental health, which developed in nearly 50% ofwomen over 50 y old, has a significant impact on their qualityof life [2]. The PFD was mainly manifested as stress urinaryincontinence and pelvic organ prolapse.

The cause of PFD is multifaceted, and pregnancy andchildbirth can lead to pelvic support tissue relaxation orrupture, which is one of the major risk factors for PFD [3,4]. Because of the wide range of symptoms and related diseases,simple clinical assessment is usually not sufficient to achievecomplete diagnosis, so the comprehensive assessment of PFDis essential.

Comparison of anatomical function and structure of femalepelvic floor between women with different delivery modesprovides potentially useful information on the risk ofsubsequently developing PFD. If we determine the effects ofdifferent delivery modes on the anatomical function andstructure of female pelvic floor, these findings will beimportant in establishing meaningful guidelines to assist bothpatients and health care providers in making decision.

Therefore, in this study, the effects of different delivery modeson the anatomical function and structure of female pelvic floorwere analyzed by pelvic ultrasonography.

Materials and Methods


A total of 194 women of childbearing age visited our hospitalfrom January 2014 to 2015 were enrolled in this study. Amongthe 194 participants, 50 cases were childless women and 144cases were fertile women. There were 84 cases of vaginaldelivery and 60 cases of cesarean delivery women. All subjectsmet the following criteria: no incontinence or childbirth beforethe symptoms of incontinence; without clinical and ultrasoundexamination identified urinary system diseases, kidney diseaseand pelvic surgery history; effectively complete the Valsalvamovement and levator ani movement. The fertile women gavebirth to a single baby.

Color Doppler ultrasound

As for parameter measurement, GE Voluson E8 color Dopplerultrasound was applied with the endocavity probe frequency of6-12 MHz. Briefly, the perineum pelvic ultrasoundmeasurement was as follows. The inspection was performedwith moderate bladder filling (50~100 ml) and stool emptied.The patients were examined at lithotomy position, and theprobe was adjusted to keep the axis of the pubic symphysis andthe horizontal line in the lower edge of pubic symphysisforming 45 degrees. Images of resting state pubic symphysis,bladder neck, urethral, vaginal, anorectal connection andmedian sagittal images under the condition of the maximumValsalva were obtained.

Parameter collection

Under the aforementioned two states, the following parameterswere measured: (1) Bladder neck-Symphyseal Distance (BSD);(2) Posterior vesicourethral angle (β), that is, the angle betweenproximal urethra and the posterior wall of the bladder (thenormal value was 90°~120°); (3) Bladder Neck Descent(BND), i.e., the difference of the bladder neck to the loweredge of the pubic symphysis between resting and the largest Valsalva state; (4) Detrusor thickness (DT), of which threepoints were measured and the average value was taken; (5)Bladder neck rotation angle, referring to the difference of theangle between the lower edge of pubic symphysis to theinternal urethral connection and the axis of symphysis pubis atthe two states (normal range <20°) [5,6].

Pelvic organ prolapse condition was observed with thehorizontal line through the lower edge of the pubic symphysisas a reference. It was taken as negative if the pelvic organ wasabove the reference line. And it was taken as positive if thepelvic organ was under the reference. Negative and positiverepresent inside and outside the pelvic.

Stress incontinence ultrasound diagnostic criteria was definedas follows: (1) At resting state, bladder urethral angle ≥ 95°;(2) At Valsalva state, the vertical distance from the bladderneck to the pubic symphysis was ≥ 2.3 cm; (3) Bladder neckrotation angle was ≥ 20°. Patients with more than 2 of the 3criteria were diagnosed as stress incontinence [7].

Statistical analysis

SPSS19.0 and GraphPad Prism 5.0 statistical software wereapplied for statistical analysis. The χ2 test was used to comparethe stress urinary incontinence distribution between twogroups. and p<0.05 was considered as statistically significant.


Baseline characteristics

In order to determine the comparability of subjects betweendifferent groups, the patient’s age, Body Mass Index (BMI),and other baseline data were collected and compared. Therewas no significant difference in age, height and BMI betweenthe childless group and the fertility group, and between vaginaldelivery and cesarean delivery subgroups (P>0.05, Table 1).These results suggest that there were no difference in thepatients in baseline characteristics.

  Unborn group (n=50) Fertility group (n=144)
Vaginal delivery group (n=84) Cesarean delivery group (n=60)
Age (y) 29.78 ± 3.79 30.24 ± 3.12 31.15 ± 2.96 0.077
Height (cm) 161.00 ± 5.47 160.73 ± 5.80 161.28 ± 6.35 0.855
BMI 21.54 ± 2.22 22.18 ± 2.40 22.5 ± 2.01 0.079

Table 1: Comparison of baseline characteristics of each group.

Perineal pelvic ultrasonography in resting state

To study the effects of gestation and delivery modes on femalepelvic floor function under resting state, indexes of pelvic floorfunction was measured. In the resting state, there were nostatistically significant differences in BSD, DT and β betweenthe childless and fertile women (P>0.05, Table 2). Similarly, for BSD and DT, the same results were observed betweenvaginal delivery group and cesarean section group.

  Unborn group (n=50) Fertility group (n=144) P
BSD (mm) 21.14 ± 2.11 20.65 ± 2.01 0.145
DT (mm) 0.28 ± 0.18 0.28 ± 0.20 0.951
β (°) 132.75 ± 8.61 135.01 ± 13.34 0.173

Table 2: Perineal pelvic ultrasonography between unborn group and fertile group in resting state.

However, the angle of the cesarean section was significantlylarger than that of the vaginal delivery group (P=0.000, Table 3). These results indicated that in the resting state, there was nosignificant change in the effects of pregnancy and deliverymodes on the pelvic floor. However, the changes of the posterior horn of the urinary bladder were different in theresting state. It is suggested that women with vaginal deliverymay have the possibility of concealed pelvic floor dysfunction.

  Vaginal delivery group (n=84) Cesarean delivery group (n=60) P
BSD (mm) 20.76 ± 2.16 20.48 ± 1.80 0.424
DT (mm) 0.27 ± 0.23 0.29 ± 0.16 0.613
β (°) 131.5 ± 14.09 139.92 ± 10.49 0

Table 3: Perineal pelvic ultrasonography between vaginal delivery group and cesarean delivery group in resting state.

Perineal pelvic ultrasonography in Valsalva state

In order to investigate whether there were differences of ineach group under Valsalva, indexes of pelvic floor functionwas measured. In the fertility group, the BND (mm), β (°) andbladder neck rotation angle were significantly higher than thatof the childless group, and there were statistical differences(P<0.05, Table 4).

  Unborn group (n=50) Fertility group (n=144) P
BND (mm) 16.26 ± 1.37 20.03 ± 2.43 0
β (°) 135.26 ± 11.51 144.05 ± 13.15 0
Bladder neck rotation angle 12.06 ± 2.22 19.76 ± 6.45 0

Table 4: Perineal pelvic ultrasonography between unborn group and fertile group in Valsalva state.

In contrast, in the vaginal delivery group, the BND (mm) andbladder neck rotation angle were significantly higher than thatof the cesarean section group, but the β (°) in the vaginaldelivery group was significantly lower than the cesareansection group (P<0.05, Table 5). These results showed thatchildbirth is one of the causes of pelvic floor dysfunction.

   Vaginal delivery group (n=84) Cesarean delivery group (n=60) P
BND (mm) 21.51 ± 1.83 17.97 ± 1.48 0
β (°) 139.90 ± 12.44 149.85 ± 11.96 0
Bladder neck rotation angle 23.96 ± 5.01 13.87 ± 2.23 0

Table 5: Perineal pelvic ultrasonography between vaginal delivery group and cesarean delivery group in Valsalva state.

Urinary incontinence

Further study was performed to illustrate the effects ofgestation and delivery modes on the incidence of stress urinaryincontinence. According to the diagnostic criteria ofhypopharyngeal urinary incontinence, in the fertility group,stress urinary incontinence was 24.31%, which wassignificantly higher than that of the childless group (P<0.05,Table 6).

  Unborn group (n=50) Fertility group (n=144) x2 p
Stress urinary incontinence 5 (10%) 35 (24.31%) 4.64 0.041
No stress urinary incontinence 45 (90%) 109 (75.69%)    

Table 6: Comparison of stress urinary incontinence in the unborn group and fertility group.

For the fertile women, in the vaginal delivery group, theurinary incontinence rate was higher than the cesarean deliverygroup. The difference between the two groups was statisticallysignificant (P<0.05, Table 7). Together, the results argued thatchildbirth may be one of the reasons for the occurrence ofstress urinary incontinence.

  Vaginal delivery group (n=84) Cesarean delivery group (n=60) x2 p
Stress urinary incontinence 26 (30.95%) 9 (15%) 4.84 0.031
No stress urinary incontinence 58 (69.05%) 51 (85%)    

Table 7: Comparison of stress urinary incontinence in the vaginal delivery group and cesarean delivery group.


Pelvic floor dysfunction could lead to the abnormal function ofthe anterior, middle and posterior pelvic cavity. The mostcommon clinical manifestation of the pelvic organ dysfunctionis postpartum stress urinary incontinence [8]. The posteriorurethral angle, urethral rotation angle, bladder neck rotationangle and increased bladder neck mobility are considered asimportant etiological factors of female stress urinaryincontinence, among which, bladder neck mobility is mostclosely related to stress urinary incontinence [9-12].Measurement of bladder and urinary tract angle, urethralrotation angle, bladder neck rotation angle, and bladder neckmobility can directly reflect the occurrence of stress urinaryincontinence.

Currently, the pelvic organ prolapse quantitative evaluationsystem published by the International Urinary Control Association is used to evaluate the pelvic organ, which mainlyrelies on the anatomical relationship to evaluate the prolapse.However, due to the complexity of the pelvic floor anatomy,the evaluation is difficult and could not reflect the functionalstatus of the pelvic organ. Transperineal ultrasonography canobserve the movement of the pelvic organs both intuitively anddynamically, and by measuring the lowest point of pelvicorgans from the pubic symphysis distance to determinewhether the pelvic organ prolapse and evaluate prolapse stages.

Some studies focus on the relationship of delivery modes andthe pelvic floor dysfunction was performed by questionnaire toobtain the data [13]. But we measured the BSD, DT, and β byultrasonography to study the perineal pelvic structure in twostates include the resting state and Valsalva state. And we notonly designed the group of vaginal delivery and cesareansection, but also designed the childless and fertile group tostudy the role of pregnancy and childbirth on the pelvic floordysfunction, while in some similar studies they usuallyperformed their studies only in vaginal delivery and cesareansection, which is the advantage of our study. The resultsshowed that the BSD, DT and β were not statisticallysignificant in the resting state between the childless womenand fertile women. The difference of β between women whowere vaginal delivery and cesarean section was statisticallysignificant in resting state. Some occult injuries may occurduring pregnancy and childbirth.

There was a significant difference in the rotation angles ofBND, β, and bladder neck between the childless and fertilegroups, the vaginal delivery group and the cesarean sectionunder Valsalva action. The incidence of stress urinaryincontinence in the fertility group was significantly higher thanthat in the childless group. The incidence of postpartum stressurinary incontinence was higher in the vaginal delivery groupthan in the cesarean section group, and the difference wasstatistically significant. Another study has obtained the similarresults, in the study the prevalence of pelvic organ prolapse,stress urinary incontinence, overactive bladder, and analincontinence was assessed in a random sample of women aged25-84 y by using the validated Epidemiology of Prolapse andIncontinence Questionnaire and they found that the risk ofpelvic floor disorders is independently associated with vaginaldelivery and cesarean delivery has a protective effect on thedevelopment of pelvic floor disorders when compared withvaginal delivery [14]. During the delivery process, under themechanical compression and expansion by the foetal head, thepelvic floor muscles degenerate and leading to shortening ofmuscle fibers and diminished contractility [5]. Pelvic floornerves are also damaged in this process which further inducesdenervation phenomenon of the pelvic floor muscle [15,16].Additionally, some obstetric factors such as the increase of thenumber of childbirth, the overlong second stage of labor, theover-large foetal weight and foetal head circumference,perineal incision, etc., all can increase the denervation of pelvicfloor and urethral striated muscle. Although the contractionforce of the pelvic floor was not affected compared with thevaginal delivery, the changes in the location of the vaginal andbladder neck were also lighter than that of the vaginal delivery.

The incidence of pelvic floor nerve injury was significantlyreduced in cesarean section as surgical operation may causeconnective tissue, fascia, muscle and ligament pelvic supportstructural abnormalities, nerve tissue damage, vascularnutritional disorders, etc., which will still affect the function ofurinary tract urinary system, leading to urinary incontinencehappened.

In summary, the changes in pregnancy itself may cause pelvicfloor dissection and functional damage. The damage of thevaginal delivery on the pelvic support is greater than that of thecesarean section. However, the protection of cesarean sectionon pelvic floor is limited. The risk of pelvic functional diseasein women taking vaginal delivery increased and pelvicultrasound can improve detection rate of postpartum womenwith pelvic floor functional disease, which, is suitable for wideapplication in clinic.



Conflicts of Interest

All authors declare no financial and non-financial competinginterests.