1. Changes in pelvic floor muscle function due to first delivery
Thorgerdur Sigurdardottir, BSc, MSc student, PT¹, Thora Steingrimsdottir, MD, PhD²,³, Arni Arnason, Associate Professor, PhD, PT¹, Kari Bø Professor, PhD, PT, Exercise scientist4, ¹Dept. of Physiotherapy, University of Iceland, Reykjavik, Iceland, ²Dept. Obstetrics and Gynecology, University of Iceland, Reykjavik, Iceland, ³Center for Antenatal
Health, Reykjavik Primary Health Care services, Reykjavik, Iceland, 4Dept. of Sports Medicine, Norwegian School of Sport Sciences, Oslo, Norway.
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Introduction
Materials and Methods
A prospective repeated measures observational study. The women were evaluated at weeks of gestation and at weeks post-partum. Thirty-six healthy primiparas with confirmed singleton pregnancy participated in the study. Strength was measured as vaginal squeeze pressure in hectoPascals (hPa) and length of contraction in seconds. The women were asked to perform; a) three maximum voluntary contractions, the strongest used for statistical analysis, b) isometric contraction, time in seconds used for analysis and c) repeated fast contractions, 15 considered maximum, number of contractions used for analysis. Results are given as mean values with 95% confidence interval (95% CI). One way ANOVA was used to compare changes in PFM function between groups of different types of delivery. Spearman´s and Pearson´s correlations was used.
P values <0.05 were considered stastically significant. SPSS software (SPSS, Chicago, USA) was used for analysis.
Pregnancy and vaginal delivery are considered to be the main risk factors in weakening the pelvic floor muscles (PFM) and development of stress urinary incontinence and pelvic organ prolaps in women. This is considered to be due to damage to fascias, ligaments, PFM and peripheral nerves, all interacting and necessary tissues for pelvic organ support and control of continence mechanism.
Aims
The main purpose of this study was to evaluate pelvic floor muscle strength and endurance before and after first childbirth and compare these parameters in women with different types of births (normal vaginal, vaginal instrumental assisted and acute cesarean section). Secondary aim was to correlate changes in PFM function with length of second stage of labor and other delivery data.
Results
Table I shows background variables. Mean birthweight and infant head circumference were not significantly different between groups. But when birthweight was compared between all infants born vaginally and acute cesarean delivery, the latter group was significantly heavier (p=0.049). We found significant differences in women's age and prepregnancy BMI. In both cases, women who had acute cesarean delivery were significantly older and had higher BMI.
Before birth, there were no significant differences between groups in PFM strength or PFM endurance (ability to hold isometric contraction and repeated fast contractions).
Figure 1 shows PFM strength before and after childbirth. The three groups showed different reduction in PFM strength: Normal vaginal, 20.1 hPa (95% CI:16.2; 24.1), instrumental vaginal, 31.4 hPa (95% CI: 7.4; 55.2) and acute cesarean, 5.2 hPa (95% CI: -6.6; 17.0) reduction. The difference was significant between normal vaginal birth vs. acute cesarean birth (p=0.028) and between instrumental vaginal birth and acute cesarean birth (p=0.003).
Figure 2 shows PFM endurance before and after childbirth. There were no significant differences between groups regarding endurance measured as holding time of PFM contractions (p=0.212). The reduction in seconds was: Normal vaginal, 83.0 sec (95% CI: 44.4; 120.1), instrumental vaginal, sec (95% CI: -39.7; 240.1) and acute cesarean, 2.4 sec (95% CI: 128.9; 255.3) of reduction.
All women were able to perform at least 15 repeated contractions both during pregnancy and after birth except one woman who was not able to contract her PFM six weeks postpartum.
Table I. Background variables for participants. Values are presented as mean (SD).
All women (n=36)
Normal vaginal birth (n=26)
Vaginal instrumental birth (n=5)
Acute cesarean section (n=5)
P values
Maternal age
(4.3)
(3.6)
(1.6)
(5.3)*
0.002
Pre-pregn. BMI
(4.3)
(4.2)
(2.5)
(3.6)*
0.044
Birthweight in g
(422)
(434)
(278)
(331)
0.112
Circumf. of infants head in cm
(1.5)
(1.5)
(1.5)
(1.0)
0.423
Figure 1. PFM strength before and after childbirth for different types of delivery
* Significantly different compared with the other groups
Figure 2. PFM endurance before and after childbirth for different types of delivery
Figures 3 and 4. Length of second stage of labour versus difference in maximal strength and difference in endurance before and after childbirth
Conclusion
This study showed that pelvic floor muscle strength was significantly decreased after vaginal delivery, both normal and with instrumental assistance, six to 12 weeks post-partum. Other aspects of PFM function i.e. endurance measured as the ability to hold isometric contraction and to repeat fast contractions are less influenced by delivery. No correlation was found between the length of second stage of labor and changes in PFM function. These results may have been influenced by a relatively small sample size and large confidence intervals, and should be interpreted with caution.
Figures 3 and 4 show correlation between length of second stage of labor and changes in PFM strength and PFM endurance respectively. There was no significant correlation between changes in PFM strength (p=0.650) and PFM endurance (p=0.810) and length of second stage of labor. No correlation was found between changes in PFM strength and endurance and perineal tear, episiotomy, perineal anesthesia, epidural analgesia, infants birthweight or head circumference in women who delivered vaginally (n=31).
This study was financially supported by the Research Fund of the Association of Icelandic Physiotherapists.