Pelvic muscle strength after childbirth

Friedman S, Blomquist JL, Nugent JM, McDermott KC, Munoz A, Handa VL. Obstet Gynecol 2012;120:1021-28.

 

Laura Scheufele PT, DPT, WCS

November 7, 2012

 Primary Aim: To estimate the effect of vaginal delivery and other obstetric exposures on pelvic muscle strength measured 6-11 years after first delivery and to investigate the relationship between pelvic muscle strength and pelvic floor disorders.

Subjects: 666 parous women who were originally recruited 5-10 years after first delivery for Mothers’ Outcomes after Delivery study returned for their second annual visit (thus 6 -11 years after first delivery). Enrolled participants plan to return annually for assessment of pelvic floor disorders.

Exclusion criteria: Maternal age younger than 15 or older than 50 years, delivery at less than 37 weeks of gestation, placenta previa, multiple gestation, known fetal congenital anomaly, stillbirth, prior myomectomy, latex allergy, and abruption. Women who developed these events during subsequent pregnancies not excluded.

 Study Design: A prospective cohort study.

 Methods:

Procedures: Obstetric exposures derived from abstraction of all delivery records for each participant performed by obstetrician on research team. If records unavailable (n=61/1285) maternal recall of delivery substituted.

Women classified into five obstetric categories: 1) all unlabored cesarean, 2) those who had at least one cesarean delivery during active labor, 3) those who had at least one cesarean delivery after complete dilation, 4) those who experienced only spontaneous vaginal deliveries, and 5) those who experienced at least one operative vaginal delivery. The operative vaginal delivery group then further subdivided into those with A) history of vacuum delivery or B) those with at least one forceps delivery. (Thus a total of 6 delivery groups). For those women who delivered vaginally other variables identified including: episiotomy, spontaneous perineal laceration, 3^rd or 4^th degree perineal laceration, delivered at least one macrosomic neonate (weight 4,000 g or more), or prolonged second stage of labor (greater than 120 minutes).

Also noted was maternal age at time of first delivery and at time of measurement, primary race, and parity. Each participant had height and weight assessed to determine body mass index.

Outcome measures:

Pelvic floor muscle strength: Assessed via Peritron vaginal perineometer. The assessor was unaware of the participant’s obstetric history and pelvic floor symptoms. With probe inserted the participant cued to “Please squeeze your pelvic muscles, as though you were trying to hold in gas.” Instructed to contract as forcefully as possible and to maintain the contraction as long as possible. Digital palpation used to confirm correct technique. Two contractions measured with 10 seconds rest in between, recording peak pressure in centimeters of water and contraction duration in seconds. Peak contraction pressure and endurance  were averaged over the 2 trials. 10 of the participants unable to perform a contraction and assigned a value of 2 cm H₂O because the lower limit of precision for the Peritron is 5 cm H₂O.

Pelvic floor symptoms: Used previously validated questionnaire Epidemiology of Prolapse and Incontinence Questionnaire.

Stages of Prolapse: POP-Q. Classified as having objective evidence of POP if the most dependent point of vaginal wall or cervix extended to or beyond the hymen.

Results:

Pelvic floor muscle strength: Peak contraction pressure and duration compared across maternal and obstetric characteristics: see Table 2. No significant differences in outcomes by age, race, parity, or obesity. Significant reduction in both strength and duration associated with macrosomnia, perineal laceration, episiotomy, anal sphincter laceration and number of vaginal deliveries. Strength alone was significantly less in women who had experienced a prolonged second stage of labor.

Only 4% of the women reported participating in Kegel exercise program, and less than 1% reported a treatment program supervised by nurse or PT.

Figure 1 depicts muscle strength across the six delivery groups. Significant differences noted in peak contraction pressure and duration across these groups (P<.001).

*No significant difference between the 3 cesarean delivery groups in peak pressures.

∗For women who had exclusively delivered by cesarean section, PFM strength significantly associated with race, specifically African-American women had a peak pressure 8.8 +/- 3.4 cm H₂O lower than women of other races (P=.010).

*The three vaginal groups showed significant reduction of peak pressure (P<.001) as compared to unlabored cesarean delivery.

*Forceps delivery significant reduced compared to vacuum delivery and spontaneous delivery (P<.001).

*Mean peak pressure for the three cesarean groups 39 cm H₂O vs mean for spontaneous vaginal delivery and vacuum delivery 29 cm H₂O vs forceps delivery 17 cm H₂O (P<.001).

*Women who had delivered at least once vaginally, peak pressure reduced 10.7 +/- 2.5 cm H₂O if they delivered by forceps when compared to those women without forceps assisted vaginal delivery (P<.001).

*Women with three or more vaginal deliveries had peak pressures of 5.1 +/- 2.5 cm H₂O lower than those women who had only delivered vaginally once or twice (P=.042).

Pelvic floor symptoms: See Table 3. Analysis of association between pelvic floor muscle strength and pelvic floor disorders stratified by delivery type, comparing women who had delivered all cesarean versus those who had delivered at least once vaginally.

*Among women who delivered exclusively by cesarean, peak contraction strength NOT associated with pelvic floor disorders except that POP was associated with higher peak pressure (P=.031).

*Among women with at least one vaginal delivery, strength was significantly less among women with anal incontinence (P=.028), symptoms of prolapse (P=.016), and prolapse on examination (P=.025).

*Women with at least one vaginal delivery and at least one pelvic floor disorder had significantly lower PFM strength when compared to those without a pelvic floor disorder (P=.012).

Discussion: This study demonstrates that there is a significant reduction in pelvic floor muscle strength in women 6-11 years after childbirth if they delivered vaginally. The lowest strength was noted in those women who had forceps assisted deliveries. This suggests that childbirth has a long lasting effect on pelvic floor muscle function a decade after childbirth. The pelvic floor symptoms associated with reduced muscle strength included POP and anal incontinence, but only in women who had delivered vaginally. Further longitudinal follow-up of this cohort will help to establish whether pelvic floor muscle weakness is central to the development of biological pathways leading to additional pelvic floor disorders.

Strengths: Large sample size and the long time-frame after the initial delivery.

Weaknesses: Could not account for all aspects of the subject’s obstetric history. No information regarding the pelvic floor muscle strength before the delivery, therefore can not rule out the observed differences were present prior to delivery and cannot conclude if the pelvic floor symptoms developed after the muscle weakness. Also there is no information reporting overall fitness level. Participants who were unable to perform a PFM contraction assigned a value of 2 cm H₂O.

Conclusion: Pelvic floor muscle strength almost a decade after childbirth is negatively affected by vaginal birth and especially if the delivery is forceps assisted.

Those women who had at least one vaginal delivery demonstrated PFM strength that was significantly less among women with anal incontinence , symptoms of prolapse, and prolapse on examination. Only 4% of the women in this study reported actively performing pelvic floor exercises.

Food for thought:

1)     If a pregnant client asks if it would be better for her to choose an elective cesarean to protect her pelvic floor muscles how would you respond?

2)     Do the results of this study have implications for the general education provided during the childbearing year considering only 4% of the women were performing pelvic floor exercise?

Additional research:

Handa VL, Blomquist JL, Knoepp LR, Hoskey KA, McDermott KC, Munoz A. Pelvic floor disorders 5-10 years after vaginal or cesarean childbirth. Obstet Gynecol 2001;118:777-84.