Vaginal birth is an established risk factor for pelvic floor trauma (Švabík, 2009; Kamisan Atan et al, 2016). This trauma may include avulsion of the levator ani muscle from the inferior pubic ramus (macrotrauma) or irreversible levator ani muscle overdistension (microtrauma) (Kamisan Atan et al, 2016).
Pelvic floor trauma is most frequently caused by overdistension during the second stage of labour, primarily affecting the pubococcygeus muscle (Lien et al, 2004; Švabík, 2009). The incidence of levator ani muscle avulsion ranges from 10–35% (van Delft et al, 2014; Kamisan Atan et al, 2016) and the use of forceps significantly increases this risk (Friedman et al, 2019). Additionally, levator ani muscle avulsion is associated with obstetric anal sphincter injury, prolonged second stage of labour (van Delft et al, 2014) and the application of pressure on the uterine fundus during the second stage of labour, also known as the Kristeller maneuvre (Youssef et al, 2019).
Levator ani muscle avulsion significantly contributes to the development of pelvic organ prolapse: 55% of women with prolapse have identifiable levator ani muscle avulsion compared to 16% of women with normal pelvic organ support (DeLancey, 2016). In addition to its impact on women's health and quality of life, pelvic organ prolapse is also one of the most common indicators for surgery. In countries of the Organization for Economic Cooperation and Development, an average of 14 in 10 000 women undergo pelvic organ prolapse surgery each year; this translates to approximately 7000 annual operations in the Czech Republic alone (Haya et al, 2018). Given the significant health and economic impacts of levator ani muscle avulsion, preventive measures designed to reduce its incidence and the associated risk factors are highly desirable.
The Aniball® (RR Medical, Troubsko, Czech Republic) is a device for antenatal training that consists of an inflatable silicone balloon connected by a tube to a mechanical hand pump and deflating valve. It is designed for use by pregnant women from 36 weeks gestation. The device is inserted into the vagina in a deflated state with the help of a water-based lubricant. It is then inflated to a comfortable size and the presence of the device leads to the creation of positive feedback in the pelvic floor area (Aniball.uk, 2020). This positive feedback is enhanced by a set of specific exercises and breathing techniques aimed at helping women relax the pelvic floor when pushing the device out of the vagina.
The device is intended to positively affect antenatal pelvic floor care, leading to a smoother course and shorter duration of the second stage of labour. These effects, along with the reduction of additional levator ani muscle avulsion risk factors, may lead to a reduction in the incidence of pelvic floor trauma. The training methodology and relaxation practices are unique to the Aniball device. The alternative commercially available vaginal balloon device is the Epi-No® (Tecsana, Munich, Germany), which has a different training methodology and aims for antenatal training. The Epi-No® device is primarily designed to strengthen pelvic floor muscles, improve perineal dilation and help practice expulsion prior to childbirth by means of a daily exercise routine implemented from 37 weeks of gestation (Kamisan Atan et al, 2016; Epino.de, 2020). The two devices are shaped differently, reflecting their different focuses. The lower part of the Epi-No® balloon is wider and designed for more significant perineal dilatation during training. Both devices, in their deflated and inflated states, are shown in Figure 1.
The Epi-No® and its effects on major pelvic floor and perineal outcomes of vaginal birth have been investigated in a number of clinical trials. Although promising results were obtained in early studies (Hillebrenner et al, 2001; Kovacs et al, 2004; Kok et al, 2004; Kavvadias and Hoesli, 2016), more robust trials subsequently could not confirm them (Shek et al, 2011; Brito et al, 2015; Kamisan Atan et al, 2016; Schreiner et al, 2018). The combination of a distinct training technique and the design of the Aniball® device may lead to less stress on perineal tissues, better pelvic floor preparation for childbirth and thus a lower incidence of birth-related complications, when compared to the Epi-No® device. However, a prospective clinical trial is needed to confirm this theory and to date, the device has been examined in only one retrospective study in which positive effects on the incidence of perineal trauma were observed (Bohatá and Dostálek, 2016).
The primary objective of the present study was to evaluate the effect of antenatal pelvic floor training using the Aniball® device on the rate of pelvic floor trauma in women with spontaneous vaginal births at term. A secondary study objective was to analyse the effects on the duration of the second stage of labour, incidence of episiotomy and birth-induced perineal trauma.
Methods
A total of 200 nulliparous women were considered for this prospective cohort intervention study between March 2017 and May 2019, and the data from 123 women were used in the final analysis. The total number of women required for the study was not determined at its commencement, as there had been no previous clinical trial examining the health effects of the device. Women were approached at week 32 of pregnancy on average (Figure 2), with the offer to participate in the study.
Recruitment
First contact was made with the help of cooperating outpatient gynecological clinics in the Ostrava region of the Czech Republic, where most regular prenatal health controls are carried out. Those who expressed an interest in participating were then referred to the Gynecology and Obstetrics Department of the Ostrava City Hospital, a secondary health center, where, after providing written consent to participate, they were assigned to one of two groups according to whether they wished to train with the device or not.
A total of 100 women were enrolled in the intervention group and provided with the device and written instructions for its use from 36 weeks of gestation. The other group of 100 women did not use the device (control group).
Intervention
Participants training with the device were instructed to perform two techniques while gradually increasing the circumference of the device: first, gaining conscious control of the device's moves (pulling the inflated balloon deeper in the vagina by contracting the pelvic floor muscles while exhaling; pushing the balloon out of vagina by relaxing the pelvic floor muscles while inhaling) and second, exercising gradual expulsion of the device in a series of inhalations.
The frequency and duration of use as well as the maximum achieved circumference were not pre-determined, although participants were encouraged not to exceed a circumference beyond which training would become painful or uncomfortable. The participants were also provided with a general recommendation for use, noting that the device was suitable to use from the end of week 36 of pregnancy. They were advised to exercise for approximately 15–30 minutes daily; however, the time and frequency of exercise were only indicative, as each participant required individual time for proper relaxation. There is no currently recognised given number of sessions, duration of session or period over which sessions should occur (van Reijn-Baggen et al, 2022). Given the goal of antenatal training with the device (proper pelvic floor relaxation), the recommendation was found to be sufficient to create positive feedback in the muscle structure.
A list of contraindications was provided in the written manual on the use of the device, to maintain participants' safety throughout the trial. These were divided into absolute contraindications (genital herpes, vaginal bleeding or acute vaginitis) and relative contraindications where a gynecologist's consultation was needed prior to exercise (vulvar varices, history of vaginal surgeries or a low-lying placenta). Given that most contraindications could occur after enrollment, participants were instructed to self-assess their health and eligibility to exercise before each training session. The only exclusion criterion for participation was the existence of a personal history of pelvic injury, for example after a car accident.
Birth after study participation
Clinical staff taking care of women in labour were blinded to participation in the study and participants were explicitly instructed not to speak about their participation in the study. No additional restrictions (for example, a written birth plan in which a woman could express her will against an episiotomy) were implemented and no specific maternity hospital was assigned to any of the women. Most women from both groups gave birth at the Ostrava City Hospital and all participating women gave birth in the Moravian-Silesian region of the Czech Republic.
A technique to protect the perineum and reduce perineal trauma and the incidence of episiotomy were applied as part of standard care at maternity wards in the Czech Republic. This ‘hands-on’ technique is a standard procedure and right-sided mediolateral episiotomy is provided in cases of clinical need, such as instrumental birth or suspected fetal compromise. This is in line with the UK's National Institute for Health and Care Excellence (2017) guidance on intrapartum care for healthy women and babies.
Data collection
After the 6 week postpartum period, all participants were contacted by phone and basic information about their birth was gathered (type of birth, gestational age at birth, spontaneous or instrumental birth). Only women who self-reported having a vaginal birth with cephalic presentation after week 37+0 without the use of a vaginal extraction method were selected for further analysis (n=123), in an attempt to eliminate most factors affecting the occurrence of levator ani muscle avulsion (eg caesarean section, forceps, ventouse) and obtain homogenous study groups. The 123 women from both study groups who were selected received an ultrasound examination of their pelvic floor 10 weeks after birth. Most similar studies also examined the pelvic floor at approximately 3 months after birth (Shek et al, 2011; Kamisan Atan et al, 2016). Clinical data associated with the birth were recorded.
Ultrasound examination and diagnosis of levator ani muscle avulsion
The ultrasound examination of the pelvic floor at rest was done in the lithotomy position using a GE Voluson E6 (GE Medical Systems, Zipf, Austria) by a member of the research team. Once the examinations were complete, all saved records were blinded (to group allocation) and assessed by a urogynecologist with experience of pelvic floor ultrasound examination using 4Dview 18.0, ext1 (GE Medical Systems, Zipf, Austria) with the criteria for 4D ultrasound levator ani muscle avulsion injury evaluation (Dietz et al, 2011).
Levator ani muscle avulsion was diagnosed using tomographic ultrasound imaging of pelvic floor records at rest with a 2.5mm interslice interval, from 5mm caudal to 12.5mm cranial of the plane of minimal hiatal dimensions, incorporating the entire puborectalis muscle. The plane of minimal urogenital hiatal dimensions was identified in the sagittal orthogonal plane, where the distance between the hyperechogenic posterior aspect of the symphysis pubis and the anterior (hyperechogenic) border of the levator ani muscle is minimal. Avulsion was defined as an abnormal muscle insertion observed in at least the three central slices (reference slice and slices 2.5–5.0mm cranial) (Dietz et al, 2017).
Clinical data
Clinical data were obtained from all participants, which included obstetric characteristics and pathologies, duration of second stage of labour and the incidence and type of birth trauma. The obstetric characteristics gathered were maternal age at birth, maternal body mass index at birth, gestational age at recruitment and at birth, newborn birth weight and whether labour was induced. Recorded obstetric pathologies were maternal obesity (defined as a body mass index >30kg/m2 at birth), gestational diabetes mellitus, hypertensive disease during pregnancy, fetal birth weight <2500g or >4000g, occiput posterior and shoulder dystocia.
The duration of the second stage of labour was defined as the interval from complete dilation of the cervix to the birth of the infant. All birth traumas were recorded and divided into three main groups: episiotomies (mediolateral, right sided), perineal tears and spontaneous birth traumas other than perineal tears (eg isolated laceration of labia or vaginal wall). In case of perineal trauma, all tears were stratified into separate subgroups according to internationally recognised categories: first-, second-, third- (subdivided into 3A, 3B and 3C subgroups according to the extent of external and internal anal sphincter muscle injury) or fourth-degree perineal tear (Sultan, 1999). If more than one type of trauma occurred in a participant, the most serious was used to assign a woman to an appropriate category. Clinical data were obtained from birth records and discharge summaries.
Data analysis
The participants' demographic and clinical characteristics were compared using two-sample t-tests on the non-parametric Wilcoxon test for continuous variables. Categorical variables were compared using Fisher's exact test. The normality of the data was tested using the Anderson–Darling test. Differences were considered significant at P<0.05. All P values were obtained using two-tailed tests and all statistical analyses were performed using the statistical language and environment R (version 4.0.2).
Ethical considerations
The study was conducted in accordance with all applicable legal requirements in the Czech Republic. Prior to commencement, the study was approved by the Ostrava City Hospital ethics committee (approval number 306). Written informed consent was obtained from all participants and personal data processing was conducted in accordance with the general data protection regulation (EU) 2016/679.
Results
Of the 200 women in the two study groups, 123 met the inclusion criteria for further examination at 10 weeks after birth: 64 in the intervention group and 59 in the control group). The inclusion criteria, with a breakdown of all excluded subpopulations, are shown in Figure 2. No statistically significant differences in sociodemographic or obstetric characteristics were observed between the two groups. The participants' obstetric characteristics and an overview of pregnancy pathologies are shown in Table 1.
Table 1. Participants' obstetric characteristics and pregnancy pathologies
| Cases (n=64) | Controls (n=59) | ||
|---|---|---|---|
| Obstetric characteristics | Mean ± standard deviation | P value | |
| Maternal age at birth (years) | 29.4 ± 3.2 | 29.5 ± 4.2 | 0.88 |
| Body mass index at birth (kg/m2) | 28.1 ± 3.9 | 29.2 ± 4.8 | 0.16 |
| Gestational age at inclusion (weeks+days) | 32+4 ± 21 | 32+2 ± 22 | 0.49 |
| Gestational age at birth (weeks+days) | 39+4 ± 7 | 39+3 ± 8 | 0.40 |
| Newborn birth weight (grams) | 3272 ± 363 | 3294 ± 377 | 0.75 |
| Induced birth (frequency, %) | 21 (32.8) | 17 (28.8) | 0.60 |
| Pregnancy pathologies | Frequency (%) | ||
| Body mass index >30 at birth | 14 (24.1) | 22 (37.3) | 0.16 |
| Gestational diabetes mellitus | 3 (4.8) | 7 (11.9) | 0.20 |
| Hypertensive disease during pregnancy | 2 (3.1) | 2 (3.4) | 1.00 |
| Fetus with birth weight <2500g | 1 (1.6) | 0 (0.0) | 1.00 |
| Fetus with birth weight >4000 g | 1 (1.6) | 0 (0.0) | 1.00 |
| Occiput posterior | 1 (1.6) | 0 (0.0) | 1.00 |
| Shoulder dystocia | 1 (1.6) | 2 (3.4) | 0.61 |
Levator ani muscle avulsion
No difference in the rate of levator ani muscle avulsion was identified between participants who used the device and those who did not (P=0.82), as shown in Table 2.
Table 2. Comparison of levator ani muscle avulstion incidence
| Frequency (%) | ||||
|---|---|---|---|---|
| Characteristic | Cases (n=64) | Controls (n=59) | Relative risk | P value |
| Total avulsions | 13 (21.0) | 11 (19.0) | 1.1 (0.7–1.5) | 0.82 |
| Left avulsions | 7 (11.0) | 3 (5.0) | ||
| Right avulsions | 3 (5.0) | 1 (2.0) | ||
| Bilateral avulsions | 3 (5.0) | 7 (12.0) | ||
| Incorrectly saved ultrasound record | 1 (2.0) | 0 (0.0) | 1.00 | |
Duration of second stage of labour and incidence of birth trauma
No difference in duration of the second stage of labour was found between the intervention and control groups (P=0.63), nor in the incidence of perineal tears (P=1.0) as well as other birth injuries (P=0.50). The incidence of episiotomy was lower in participants who used the device (P=0.007). An obstetric anal sphincter injury occurred only in one case (grade 3A), which was in the control group. The results are shown in Table 3.
Table 3. Comparison of duration of second stage of labour, incidence of episiotomy, perineal tears and other spontaneous birth injuries
| Frequency (%) | ||||
|---|---|---|---|---|
| Characteristic | Cases (n=64) | Controls (n=59) | Relative risk | P value |
| Median duration of second stage of labour (minutes) (interquartile range) | 14 (15) | 15 (12) | 0.63 | |
| Right side mediolateral episiotomy | 22 (34.4) | 35 (59.3) | 0.58 (0.39–0.86) | 0.007 |
| Total perineal tears | 15 (23.4) | 13 (22.0) | 1.06 (0.55–2.04) | 1.00 |
| First degree perineal tears | 8 (12.5) | 4 (6.8) | 1.84 (0.59–5.80) | 0.37 |
| Second degree perineal tears | 7 (10.9) | 8 (13.5) | 0.81 (0.31–2.08) | 0.78 |
| Third degree perineal tears (3A) | 0 (0.0) | 1 (1.7) | 0.48 | |
| Higher perineal tears (3B or higher) | 0 (0.0) | 0 (0.0) | ||
| Other birth injuries | 14 (21.9) | 10 (16.9) | 1.29 (0.62–2.68) | 0.51 |
Discussion
The main findings of this study were that antenatal training using the Aniball® device from 36 weeks of gestation does not lead to a statistically significant reduction in the rate of levator ani muscle avulsion, birth-induced perineal tears or other spontaneous birth traumas, nor in the duration of labour in nulliparous women with vaginal birth at term. The training was associated with a statistically significant reduction in the rate of episiotomies.
The ongoing debate regarding the possible effects of vaginal birth on women's postpartum health continues to create demand among both prospective mothers and physicians for procedures and methods capable of mitigating or eliminating its adverse effects (Kamisan Atan et al, 2016; Aasheim et al, 2017; Abdelhakim et al, 2020). Areas that have been investigated include intrapartum pelvic floor trauma and birth-induced perineal trauma. With respect to intrapartum pelvic floor trauma and its prevention, the Epi-No® device has been examined in detail. In spite of initially promising results indicating a shortening of the second stage of labour and lower incidence of levator ani muscle trauma (Hillebrenner et al, 2001; Kavvadias and Hoesli, 2016), no protective effect has been confirmed in more robust randomised controlled trials (Shek et al, 2011; Kamisan Atan et al, 2016). In terms of the Aniball® device, no significant difference in the rate of birth-induced levator ani muscle macrotrauma has been observed prior to this study.
In comparison with pelvic floor trauma, birth traumas and factors influencing their occurrence are examined in greater detail (Aasheim et al, 2017; Abdelhakim et al, 2020). A number of procedures are being investigated to reduce trauma incidence and severity, which can be subdivided into antepartum and intrapartum methods. Vaginal balloon devices, which are antepartum procedures, include the Epi-No® and Aniball® devices. Similarly to the results on pelvic floor trauma, the Epi-No® device showed initially promising results (Kovacs et al, 2004; Kok et al, 2004) that were not subsequently confirmed (Kamisan Atan et al, 2016; Brito et al, 2015). The Aniball® device has to date been examined in only one retrospective study with positive results. Its use was linked to a reduction in the episiotomy rate and an increase in the intact perineum rate (Bohatá and Dostálek, 2016). In this regard, the results of the present study are in agreement with previously published data.
With respect to affecting duration of the second stage of labour, the studied methods can be divided into antepartum and intrapartum procedures. To date, the only studies to have been published on balloon devices in the antepartum period have examined the effect of the Epi-No® device. As with the areas previously discussed, the initially established positive effects of shortening the second stage of labour (Hillebrenner et al, 2001) were not subsequently confirmed (Kamisan Atan et al, 2016; Schreiner et al, 2018). For the Aniball® device, its antepartum use has not proved to have a positive impact on the duration of the second stage of labour.
Although there has been a retrospective study examining the outcomes of antenatal pelvic floor training with Aniball® to date, it did not distinguish between Aniball® and Epi-No®; the published positive effects on the episiotomy and intact perineum rate were contributed to vaginal balloon devices as a group (Bohatá and Dostálek, 2016). Thus, the present study is the first to report solely on the Aniball® device and its effects on major phenomena associated with vaginal birth, including the incidence of intrapartum levator ani muscle avulsion, episiotomy, spontaneous birth trauma and duration of the second stage of labour. Although its use did not lead to a significant reduction in the incidence of levator ani muscle macrotrauma, did not significantly shorten the second stage of labour and did not lead to a significantly lower incidence of perineal tears and other spontaneous birth traumas, the reduction in the number of episiotomies constitutes a significant benefit.
These findings are essential for a better understanding of the relationship between antenatal pelvic floor training using vaginal balloon devices, the course of labour and its possible consequences. In addition, the present study provides important background information for further research with respect to the Aniball® device.
Strengths and limitations
The primary strength of this study was the selection of analysed women. The exclusion criteria successfully reduced the influence of most negative or positive factors on the development of pelvic floor trauma (eg caesarean section, forceps, premature birth associated with a generally lower birth weight of the newborn). The fact that only nulliparous women with spontaneous cephalic births after week 37+0 were studied in detail increases the reproducibility of the study with regard to a majority of the target population (prospective mothers with potential interest in antenatal training using a vaginal balloon device). The blinded evaluation of all ultrasound recordings by an expert urogynecologist with many years experience with diagnosis of pelvic floor disorders constitutes another significant strength of this study.
However, this study also has several limitations. First, this was not a randomised study. Women were free to decide whether they wished to be included in the intervention or control group, which may have subsequently influenced their attitude and approach to the intervention during the course of the study. This design was driven by an unofficial survey among pregnant women. In most cases, women had already decided whether they wanted to train with the device or not and only a small fraction were undetermined. As a result of time constraints, it was unfeasible to aim the study at the undecided group for randomisation, as it would take much more time to reach the same sample size.
Second, women were in no way restricted in their capacity to compose birth plans. This may have influenced the clinical staff during childbirth in the case of women who chose to use a birth plan (for example, they may have explicitly expressed a wish not to have an episiotomy in any case, which may then influence clinical staff 's attitude to this procedure). This may have affected the results, as in the authors' experience, women choosing to train with the device antenatally more commonly seek alternative approaches to pregnancy and childbirth. Thus, they may more frequently reject an episiotomy than the general population. These women also more frequently compose birth plans, and there are no data on how many participants had a birth plan or how many explicitly expressed that they did not want an episiotomy, which may impact the results.
Conclusions
Antenatal pelvic floor training with the Aniball® device in nulliparous women from 36 weeks of gestation with spontaneous cephalic vaginal birth at term has not been found to bring a statistically significant reduction in the rate of levator ani muscle avulsion during childbirth, duration of the second stage of labour or incidence of perineal tears or other spontaneous birth traumas. However, it may reduce the necessity of an episiotomy. Further research based on more robust trials is needed to confirm these results.
Key points
- The present study examined birth outcomes in Czech nulliparous women with spontaneous cephalic vaginal birth at term, comparing training with a balloon device antenatally or not training with a device.
- There was no statistical difference in the incidence of levator ani muscle avulsion or spontaneous perineal tears between women who trained with a balloon device antenatally and those who did not.
- However, a statistically significant lower incidence of episiotomies was associated with device use.
- Further research is needed to confirm the outcomes of this study.