Int
Urogynecol J. 2013, June 08 published online
September
11, 2013
Ann
Dunbar PT, DPT, MS, WCS
Primary Aim: To investigate the influence of vaginal
resting pressure (VRP), PFM strength (measured as maximum voluntary contraction
(MVC)), and endurance at midpregnancy on delivery outcomes.
Subjects: At week 18 of their first pregnancy, 300
women were recruited at the time of their US
Study Design: Prospective cohort
Methods:
·
Assessment
of PFM
o
At
gestational week 20.8 (± 1.4) participants were taught how to perform correct
PFM contraction by 2 trained PTs
o
Defined
as a squeeze around pelvic openings with lift of perineum
o
Verified
by observation of inward movement of perineum and by vaginal palpation
·
Measurement
of VRP, PFM strength, and endurance
o
PFM
strength (measured as MVC) and endurance were assessed utilizing high precision
pressure transducer connected to balloon catheter (intra-observer reliability
previously established)
o
Contractions,
done in supine hooklying, were considered correct only with simultaneous inward
movement of perineum
o
PFM
endurance assessed as the area under the curve during effort to hold for 10s
o
Participants
completed 3 MVC followed by short resting period and then 1 holding period
·
Outcome
variables / Definitions
o
Data
extracted from hospital’s electronic birth records
o
Cesarean
sections divided into 2 groups, elective or acute, and women undergoing
elective Cesarean were excluded from analysis
o
Second
stage labor: interval between full cervical dilatation to birth of child
§
Prolonged
second stage considered to be more than 2 hours
o
Instrumental
vaginal delivery: vacuum or forceps assisted or both
§
Due
to low rate of forceps deliveries, these variables were reported together
o
Perineal
tears (Sultan et al, 1994)
§
Third
degree: partial or complete disruption of anal sphincter muscles (IIIa-c)
§
Forth degree: when tear
also included disruption of anal epithelium
o
Episiotomy:
left mediolateral incision per common Norwegian practice
o
Induction:
any non-spontaneous start of labor
·
Data Analysis:
o
Demographic
variables reported as means with SD or numbers with percentages
o
Mann-Whitney
or independent sample t-test used to report differences between PFM variables
with outcome variables expressed as means with 95% confidence intervals (CI)
o
Logistic
regression used to report associations between PFM variables with outcome variables
expressed as crude or adjusted odds ratios (cOR and aOR).
o
Authors
adjusted for maternal age, prepregnancy BMI, birth weight, induction of labor,
epidural, and head circumference
o
The
p value set ≤ 0.05; alpha level at
0.01 for Bonferroni adjustment for 5 comparisons
Results
Characteristics
of participants (Table 1): mean age 28.7 (4.3) and prepregnancy BMI 23.8 (3.9)
kg/m2 ; college level education in 75.5%;
married 95.7%; smoking prepregnancy 25.3% and during 5.1%
Labor
and delivery outcomes (Table 2): normal vaginal delivery 69.7%; Cesarean
14.1%; Instrumented delivery 14.84%; Episiotomy 26.4%; Perineal tear : none-- 59.2%; 1st deg.--13.4%; 2nd
deg—24.2%; 3rd and 4th deg—3.3%. Prolonged 2nd stage: 13.7%
Description
of PFM variables by delivery outcome variables (Table 3): expressed as mean
differences in VRP, PFM strength and endurance at midpregnancy in women with
and without prolonged 2nd stage, acute Cesarean section, instrumented
vaginal delivery, 3rd/4th deg. tear, episiotomy
·
Women
with prolonged 2nd stage of labor had statistically significantly
higher resting pressure at midpregnancy (p≤0.01)
·
VRP
did not affect any other delivery outcomes
·
No
significant differences in PFM strength or endurance with any delivery
variables (Table 4)
·
In
Table 5, cOR and aOR showed significant association only between VRP
(midpregnancy) and prolonged 2nd stage of labor (no other
associations were significant)
Strengths: Large sample size, minimal loss to follow up
and methodologies using of valid and reliable PFM assessment and clinicians
assessing delivery outcomes blinded to PFM variables.
Limitations: Small number of
acute Cesarean and perineal trauma deliveries (was comparable to rate at that hospital,
however). PFM assessment could have been
done closer to delivery.
Discussion
Main Findings: PFM strength and
endurance assessed midpregnancy in nulliparous women, did not have an effect on
delivery outcomes (rate of acute Cesarean, instrumental vaginal delivery,
prolonged second stage, 3rd and 4th degree tears, and
episiotomy). VRP at midpregnancy was
significantly associated with prolonged 2nd state of labor but none
of the other delivery outcomes. Authors report on previous studies comparing
women assigned to PFMT or controls, also demonstrated no harmful impact on
delivery variables.
High VRP: Was associated
with prolonged stage II when adjusting for confounding factors. Authors note
this association was low and it could be argued, not clinically relevant.
Authors note past research has demonstrated a relationship between PFM strength and
endurance and PFM thickness which is why they chose to use the term VRP rather
than PFM resting pressure. Structures such as fat or viscera could also contribute
to VRP. Authors discuss study demonstrating a correlation between VRP and
levator hiatus (LH) area in women with POP though it accounted for only 26% of
the variance in LH after controlling for age, parity, BMI, and socioeconomic
status.
Clinical
Application
1)
Prolonged 2nd stage of labor is a risk factor for future PFM
dysfunction and though the difference is small, this study suggests that
increased midpregnancy VRP may contribute.
Does this finding affect your treatment program for pregnant patients?
What would you tell a pregnant patient about strengthening her PFM?
2)
PFM strength and endurance decrease with vaginal delivery (see Additional
Reading section). Continent women at
midpregnancy seem to be better at 6 weeks postpartum because they “have a
better starting point.” How can we use
this information in our own practices?
3)
The authors state the early timing of the PFM assessment was a weakness for
their study. Do you think doing a PFM assessment closer to delivery would have
made a difference?
Additional Reading
Hilde
G, Staer-Jensen J, Siafarikas F, et al: Impact of childbirth and mode of
delivery on vaginal resting pressure and on pelvic floor muscle strength and
endurance. Am J Obstet Gynecol 2013;208:50e1-7.
(Same
cohort and methodology as aforementioned study). Results demonstrated for
normal and instrumental vaginal deliveries, PFM strength was reduced by 54% and
66%, endurance by 53% and 65% and VRP was reduced by 29% and 30% respectively.
Comparing Cesarean versus normal and instrumented deliveries, differences for
all PFM measures were significant. (Significant and pronounced reduction in all
PFM measurements for vaginal delivery modes (normal and instrumented)). At both midpregnancy and 6 wks postpartum,
PFM strength and endurance were significantly higher in urinary continent women
compared to women with urinary incontinence. Multivariate analysis demonstrated
delivery mode was most important factor for change in PFM variables.
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