Methods
This is an observational retrospective study, consecutively screening
primiparas who conducted the regular prenatal examinations and delivered
between January 2019 and December 2020 at the International Peace
Maternal and Child Health Hospital in Shanghai.
This study was approved by the
Medical Science Ethics Committee of the International Peace Maternal and
Child Health Hospital.
Our study screened study subjects, who
experienced singleton delivery as
primipara, and whose neonates less than 4000g, who had cesarean section
or vaginal delivery with / without perineum laceration limited in degree
II. Meanwhile, we excluded the subjects who was younger than 18-year-old
or older than 50-year-old; who had premature birth at fewer than 28
weeks gestational age; who conceive a
fetus with known congenital anomalies; who had stillbirth; who had at
moment vaginitis and pelvic inflammatory disease; who had chronic
coughing and chronic constipation; who had other systemic comorbidities
(e. g. heart, liver and kidney disease, hematological disease,
respiratory disease, etc.).
In general, we set up two study groups, cesarean section delivery group
(CD) and vaginal delivery group (VD), in order to analyze the impact of
these two main modes of delivery on PFD. Furthermore, the vaginal
delivery group were separated into four subgroups, including Group A
with intact perineum or first-degree perineum laceration, Group B with
second-degree perineum laceration, Group C with lateral episiotomy, as
well as Group D with forceps delivery.
The
clinical data of pregnancy and delivery were obtained from electronic
medical records system. At 6–8 weeks postpartum, all
subjects underwent the routine
assessments, which included the inquiry of medical history,
gynecological examination and the
sEMG evaluation of
the PFM function.
PFM function was evaluated with vaginal palpation and sEMG. All patients
routinely were offered the instructions and information about sEMG
before the examination, by a trained urogynecologist of the Pelvic Floor
Diagnosis and Treatment Center. Participants were in supine position and
requested to be relaxed in the whole process of the sEMG examination.
During the process, the automated protocol software provided the
participants real-time instruction by voice messages and figures on
monitor, with which the participants could relax or contract the PFMs
accordingly. The sEMG facility used in this study was a Biofeedback
electrical stimulator made by Nanjing Mai Lan De Medical Technology,
Ltd, Nanjing, China (mode: MLD A2). It has 2 channels, composed of
Channel 1 to acquire the electromyographic signal by inserting an
intravaginal sensor probe into the vaginal cavity; and Channel 2, to
acquire the EMG signals from abdominal muscles by electrode patches
attaching to the abdomen.
With the collected amplified the EMG signal, muscle fiber recruitment
and relaxation time, muscle fiber type and fatigue, all these data were
processed and presented visible interpreted curves on the computer
interface by certain software. The combination of channel 1 and 2 were
processed and analyzed the percentage of abdominal muscle engagement.
A modified Glazer protocol was
used to analyze the pelvic floor sEMG value. The modified Glazer
Protocol includes 4 activities, and the signal parameters were
calculated for each activity.
1. The rest (pre-baseline) phase:
the subjects were instructed to feel
the pelvic floor muscle in rest remaining
for 10-second. To test the PFM
tension in a relaxed state.
Average Mean Amplitude (µV)
2. The phasic (flick) contraction phase: the subjects were instructed to
quickly contract the PFM, and then fully relax the PFM immediately after
contraction (five 2-second contraction with a 2-second rest in-between).
To test muscle strength and reaction velocity of the fast muscle
fibers (Class II fibers).
Average Peak Amplitude (µV): the mean value of 5 contractions
Time Before Peak (s): the mean value of 5 contractions
Time After Peak (s) - the mean value of 5 contractions
3. The tonic contraction phase:the subjects were instructed to contract
the PFM as strongly as possible and hold the contraction for 10
seconds,then fully relax the PFM after contraction for 10 seconds. To
test muscle strength and contractile stability of the slow muscle fibers
(Class I fibers).
Average Mean Amplitude(µV) - the mean value of 5 contractions
Mean Amplitude Variability (%)
4. The rest (post-baseline) phase: the subjects were instructed to feel
the PFM in rest for 10-second. To
test the PFM tension in a relaxed state.
Average Mean Amplitude (µV)
All the relevant data were filled in Excel to establish a database.
Statistical analysis was performed
using SPSS 26.0. If the date showed
normal distribution and the equal variance, the measurements presented
as x±s and were analyzed by t-test for comparisons between two groups
and one-way ANOVA for comparisons among multiple groups. Those data that
did not meet a normal distribution or a equal variance, presented as the
median [M (P25, P75)], the Mann-Whitney U-test was used for
comparisons between two groups, while the Kruskal-Wallis rank sum test
was used for comparisons among multiple independent samples.
P<0.05 was considered
statistically significant.