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The Effect of Childbirth on Pelvic Organ Mobility

From the School of Women’s and Childrens’ Health, University of New South Wales, Randwick; and Royal Hospital for Women, Sydney, Australia.

Address reprint requests to: H. P. Dietz, MD, FRANZCOG, DDU, 1/68 Brook Street, Coogee 2034 NSW, Australia; E-mail: hpdietz{at}bigpond.com.

	ABSTRACT

TOP ABSTRACT MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
OBJECTIVE: To study the effect of child birth on pelvic organ mobility in a prospective observational study.

METHODS: A total of 200 women were recruited early in their first ongoing pregnancy and examined by translabial ultrasound in the first/early second trimester, the late third trimester, and 2–5 months postpartum. Peripartal changes in the mobility of urethra, bladder, cervix, and rectal ampulla were correlated with labor and delivery data.

RESULTS: A total of 169 women returned postpartum (84.5%). Highly significant increases in organ mobility on Valsalva were found after vaginal delivery (P <.001), with forceps causing the most marked changes. Length of second stage, especially active second stage, correlated with an increase in pelvic organ descent (P = .03 to P < .001). The influence of gestational age, length of first stage, and birth weight did not reach significance.

CONCLUSION: Vaginal birth, in particular operative delivery, negatively affects pelvic organ support. This appears to be true for all three vaginal compartments. All forms of cesarean delivery were associated with relatively less pelvic organ descent. These findings may partly explain the protective effect of elective cesarean delivery for future symptoms of pelvic floor disorders.

The etiology of genuine stress incontinence and female pelvic organ prolapse is thought to be multifactorial.¹ Traumatic damage to fascial and/or muscular support structures during vaginal childbirth may be an important contributor to the development of stress incontinence and prolapse, with congenital, hormonal, and other factors also contributing.²

There is increasing evidence to support the concept of permanent pelvic floor damage after childbirth. So far, this evidence is mainly based on neurophysiologic studies implying pudendal nerve damage.³ However, the value of pudendal nerve neurophysiology is by no means undisputed,⁴ and reinnervation is the rule rather than the exception. More convincing evidence is available for anal sphincter trauma.⁵

As regards damage to fascial structures, it has frequently been assumed that at least some of the distinct fascial defects seen in later life, such as paravaginal defects,⁶ can be attributed to delivery-related trauma. With the more widespread use of translabial ultrasound, it has recently become possible to investigate the effects of vaginal delivery on the supports of the anterior vaginal wall and bladder neck.^7–10 Results to date have been inconclusive and conflicting, probably because of methodologic difficulties and a lack of numbers. In this prospective observational study, the authors attempted to define the extent of trauma to pelvic support structures by measuring pelvic organ descent on maximal Valsalva maneuver before and after delivery in a cohort of nulliparous women.

	MATERIALS AND METHODS

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A total of 200 nulliparous women were recruited in the antenatal clinic of a large tertiary hospital. They were seen three times–at 6–18 weeks’ gestation, at 32–37 weeks’ gestation, and for the third and last visit at 2–5 months postpartum. Appointments consisted of an interview, paper towel test, flowmetry, and translabial ultrasound. For the purposes of this study, third-trimester and postpartal ultrasound data as well as labor and delivery data were analyzed to determine the influence of childbirth on pelvic organ mobility.

An assessment of the mobility of urethra, bladder, cervix, and rectal ampulla was performed by translabial ultrasound, with the patient supine and after voiding. Detailed descriptions of the methodology^11,12 have recently been published. Both rotation of the proximal urethra and bladder neck descent have been shown to be strongly associated with genuine stress incontinence in urogynecologic patients.¹³ The following ultrasound systems were used for B-mode imaging with 3.5–7-MHz curved array transducers: Toshiba EccoCee (Toshiba Australia, North Ryde, NSW, Australia), ATL HDI 3000 (Philips Medical Systems Australasia, Sydney, NSW, Australia), Hitachi EUB 240 (Hitachi Australia, North Ryde, NSW, Australia), and Dornier AI 5200 (Meditron, Ringwood, Vic., Australia). Because electronic calipers are standardized for reproducibility according to industry-wide standards, measurements are generally regarded as comparable between transducers and systems.¹⁴ Translabial imaging was performed by covering the transducer with a glove and placing it in a midsagittal orientation on the perineum. The resulting view is shown in Figure 1, with Figure 2 illustrating a case of markedly increased pelvic organ mobility after vaginal delivery. Measurements were performed on screen or on printouts. The inferoposterior margin of the symphysis pubis was used as a fixed point of reference. Differences between measurements at rest and on Valsalva was recorded as proximal urethral rotation in degrees and bladder neck descent in millimeters. The maximal descent (= degree of prolapse) reached by bladder (ie, a cystocele if one is present), cervix, and rectal ampulla (or, if present, a rectocele) on Valsalva was recorded as a positive figure (in millimeters) if the leading edge of the organ remained above the inferoposterior margin of the symphysis, and as negative if below. For a description of the ultrasound parameters used, see Table 1.

View larger version (27K): [in this window] [in a new window]   Figure 1. Field of view of translabial ultrasound (midsagittal orientation). Dietz. The Effect of Childbirth. Obstet Gynecol 2003.

View larger version (61K): [in this window] [in a new window]   Figure 2. Antepartum (left) and postpartum (right) maximal Valsalva maneuvers as imaged by translabial ultrasound. There is a marked increase in pelvic organ mobility in this primiparous woman. The clinical equivalent of postpartum findings are a first-degree cystourethrocele and a first-degree rectocele with significant perineal relaxation. Dietz. The Effect of Childbirth. Obstet Gynecol 2003.

Interobserver variability for the main outcome parameter bladder neck descent (in millimeters) was recently determined by the authors as a coefficient of variation of 0.08 and an intraclass correlation coefficient (2,1) of .98 for evaluation of the same Valsalva maneuver by different examiners. A coefficient of variation of 0.20 or an intraclass correlation coefficient (2,1) of .79 were determined for evaluation of different Valsalva maneuvers by two blinded examiners (unpublished data). Labor and delivery details were gathered through data collection sheets attached to the patient’s antenatal record and checked or completed through access to hospital notes and the institutional obstetric database. Total duration of the second stage of labor was defined as the interval between confirmation of full cervical dilatation and delivery of the infant. Active second stage was taken as the time between commencement of active pushing and delivery. Passive second stage was defined as the difference between total and active second stage. Ethics Committee approval had been obtained from the local Ethics Committee (SESAHS EC approval 99/184).

Sample size calculations were based on a pilot study performed under the supervision of the first author (unpublished data). In this pilot data, the group-specific means and standard deviations (SD) were 15.5 mm (SD 10.3) for normal vaginal delivery, 13.5 mm (SD 10.6) for cesarean delivery, and 25 mm (SD 9.6) for vaginal operative delivery. Assuming a dropout rate of 33% and proportions of 21% cesarean delivery, 15% vaginal operative deliveries, and 64% normal vaginal deliveries (data for Royal Hospital for Women, 1998), a sample size of 200 recruits was estimated to provide over 95% power to detect a statistically significant difference between normal vaginal delivery versus forceps/vacuum as well as cesarean delivery versus forceps/vacuum as regards bladder neck descent ( = .05). All data except length of second stage were normally distributed as assessed by Kolmogorov–Smirnov testing. The t test statistics were used for continuous, normally distributed parameters. Spearman correlation coefficient statistics were used to correlate length of second stage with ultrasound data. Analysis of variance followed by Tukey multiple comparisons were employed to test the outcome of delivery mode against explanatory parameters. A P < .05 was taken as indicating significance.

	RESULTS

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Of the originally recruited 200 women, 173 were seen for an assessment at 32–38 weeks’ gestation. Table 2 shows descriptive statistics for the ultrasound parameters used. Cervix and rectum were not clearly seen in one and nine cases, respectively. Delivery information was available for all 173 women. Ninety-nine were delivered by normal vaginal delivery (57%), nine underwent elective or prelabor cesarean delivery (5%), and 36 had an intrapartum cesarean delivery (21%). Indications for cesarean delivery were failure to progress in first stage (n = 18), failure to progress in second stage (n = 8), fetal distress (n = 7), breech presentation (n = 5), failed induction (n = 4), brow presentation, placenta previa, and back pain (n = 1 each).

One hundred sixty-nine women attended a visit 2–5 months postpartum at which time an identical assessment was performed. Eight of those 169 had missed the previous appointment. Table 3 lists demographic data for attenders and nonattenders. Of 31 nonattenders, 12 had moved, ten were unwilling to continue, four had miscarried, two had had a termination of pregnancy, and three were lost to follow-up. Nonattenders were significantly younger but did not differ for other demographic parameters. The average enrollment period (time interval between first and last appointment) was on average 282 days (209–417) days. On ultrasound imaging, cervix and/or rectum were not reliably imaged in six cases each. Table 4 shows descriptive statistics for pelvic organ mobility at the postpartum visit.

	DISCUSSION

TOP ABSTRACT MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
There is increasing evidence for the concept of permanent pelvic floor damage after childbirth.¹⁵ Epidemiologic studies consistently show associations between parity on the one hand and stress incontinence or female pelvic organ prolapse on the other hand.^16,17 Direct clinical evidence to date is mainly based on neurophysiologic studies implying pudendal nerve damage³ and imaging data on anal sphincter trauma.⁵ Several papers have been published investigating the effect of childbirth on bladder neck mobility relative to the symphysis pubis, assumed to be a measure of integrity of anterior compartment fascial structures. However, results to date have been inconclusive.

Meyer et al,⁹ in a prospective study on approximately 150 nulliparous women, showed that bladder neck mobility was significantly increased after all vaginal deliveries with no differences between forceps and normal vaginal delivery. However, low measurements for bladder neck descent (means of 10–13 mm) raise doubts regarding the methodology of this study. Bader et al⁷ found significant differences both between cesarean delivery and vaginal delivery and between normal and operative vaginal delivery with regard to mobility of the bladder neck, although this paper only reported postpartum imaging. Another small study also confirmed the finding of increased mobility of the bladder neck after vaginal childbirth.⁸

King and Freeman¹⁰ found no association between delivery mode and changes in ultrasound measurements. An explanation for this may be found in the methodology of this study: Patients were examined with a full bladder, upright and in stirrups, with a Valsalva force standardized at 30 mm Hg or 40 cm H₂O with the help of a spirometric device. All these factors would minimize hypermobility^18,19 and therefore the ability of the study to detect the effect of delivery-related variables.

None of the mentioned studies investigated the central or posterior compartments, which is straightforward and requires no methodologic modifications.¹² Central compartment prolapse is measured by demonstrating descent of the leading edge of the cervix on Valsalva. This is easier in pregnancy because the cervix is enlarged and more structured, showing a layered appearance. The posterior compartment can be assessed sonographically by demonstrating descent of the rectal ampulla. A rectocele results in ampullary contents developing in a ventrocaudal direction. The correlation between clinical assessment, the recently developed prolapse quantification system of the International Continence Society, and ultrasound quantification is not as close as for the other two compartments.¹² Nevertheless, imaging is likely to provide better quantitative information than either the prolapse quantification system of the International Continence Society or clinical staging because the actual position of organs rather than the surface topography of the vagina is assessed.²⁰

The authors believe that the study presented here goes a long way towards furnishing proof for the hypothesis that vaginal childbirth negatively affects the support tissues of pelvic organs. Vaginal delivery resulted in highly significant changes to the mobility of urethra, bladder neck, posterior bladder wall, cervix, and rectal ampulla/anterior rectal wall. These changes correlated with length of second stage and with delivery mode.

All forms of cesarean delivery, but especially prelabor cesarean, were associated with relatively less pelvic organ descent, with postpartum measurements in women after prelabor cesarean delivery practically returning to early pregnancy values. These findings may partly explain the protective effect of elective cesarean delivery for future symptoms of pelvic floor disorders. However, only randomized controlled intervention trials will provide definite proof of any such effect.

Changes in organ mobility imply alterations in the biomechanical properties of support structures. These may be attributed to stretching or disruption of fascial and/or muscular tissues, and the study presented here does not allow conclusions regarding the exact nature of these changes. It is also unclear as to whether such alterations are associated with symptoms in the long term, and whether pregnancy itself causes (permanent or transitory) biomechanical changes predating the delivery. Further work will be necessary to elucidate these issues.

	Footnotes

 
HPD was supported by a Research Fellowship of the Royal Australian and New Zealand College of Obstetricians and Gynecologists funded by Mayne Nickless Ltd for the duration of this study.

doi:10.1016/S0029-7844(03)00476-9

Received October 22, 2002. Received in revised form February 12, 2003. Accepted March 13, 2003.

	REFERENCES

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1. Wilson PD, Herbison RM, Herbison GP. Obstetric practice and the prevalence of urinary incontinence three months after delivery. Br J Obstet Gynaecol 1996;103: 154–61.[Medline]

2. Swift SE, Pound T, Dias JK. Case-control study of etiologic factors in the development of severe pelvic organ prolapse. Int Urogynecol J 2001;12:187–92.

3. Jozwik M, Jozwik M. Partial denervation of the pelvic floor during term vaginal delivery. Int Urogynecol J 2001;12: 81–2.

4. Vodusek DB. Clinical neurophysiological tests in urogynecology. Int Urogynecol J 2000;11:333–5.

5. Sultan AH, Monga AK, Stanton SL. The pelvic floor sequelae of childbirth. Br J Hosp Med 1996;55:575–9.[Medline]

6. Richardson AC, Lyon JB, Williams NL. A new look at pelvic relaxation. Am J Obstet Gynecol 1976;126:568–73.[Medline]

7. Bader W, Kauffels W, Degenhardt F, Schneider J. Postpartum ultrasound morphology of the pelvic floor [in German]. Geburtshilfe Frauenheilkd 1995;55:716–20.[Medline]

8. Peschers U, Schaer G, Anthuber C, DeLancey JO, Schuessler B. Changes in vesical neck mobility following vaginal delivery. Obstet Gynecol 1996;88:1001–6.[Abstract]

9. Meyer S, Schreyer A, De Grandi P, Hohlfeld P. The effects of birth on urinary continence mechanisms and other pelvic-floor characteristics. Obstet Gynecol 1998;92: 613–8.[Abstract]

10. King JK, Freeman RM. Is antenatal bladder neck mobility a risk factor for postpartum stress incontinence? Br J Obstet Gynaecol 1998;105:1300–7.[Medline]

11. Dietz HP, Wilson PD. Anatomical assessment of the bladder outlet and proximal urethra using ultrasound and videocystourethrography. Int Urogynecol J 1998;9:365–9.

12. Dietz HP, Broome J, Haylen BT. Ultrasound quantification of uterovaginal prolapse. Ultrasound Obstet Gynecol 2001;18:511–4.[Medline]

13. Dietz HP, Clarke B, Herbison P. Bladder neck mobility and urethral closure pressure as predictors of genuine stress incontinence. Int Urogynecol J 2002;13:289–93.

14. Kremkau FW. Diagnostic ultrasound: Principles and instruments. Philadelphia: Saunders, 1998.

15. Davila GW. Informed consent for obstetrics management: A urogynecologic perspective. Int Urogynecol J 2001;2: 289.

16. Mant J, Painter R, Vessey M. Epidemiology of genital prolapse: Observations from the Oxford Family Planning Association Study. Br J Obstet Gynaecol 1997;104:579–5.[Medline]

17. Olsen AL, Smith VJ, Bergstrom JO, Colling JC, Clark AL. Epidemiology of surgically managed pelvic organ prolapse and urinary incontinence. Obstet Gynecol 1997;89:501–6.[Abstract]

18. Dietz HP, Wilson PD. The influence of bladder volume on the position and mobility of the urethrovesical junction. Int Urogynecol J 1999;10:3–6.[Medline]

19. Dietz HP, Clarke B. The influence of posture on perineal ultrasound imaging parameters. Int Urogynecol J 2001;12: 104–6.

20. Kenton K, Shott S, Brubaker L. Vaginal topography does not correlate well with visceral position in women with pelvic organ prolapse. Int Urogynecol J 1997;8:336–9.

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