Atraumatic forceps-guided insertion of the cervical pessary: a new technique to prevent preterm birth in women with asymptomatic cervical shortening

Introduction

Preterm birth (PTB), one of the main causes of neonatal morbidity and mortality, is any live birth before 37 weeks of gestation (WG), which occurs in almost 10 % of all births and places a huge burden on national economies [1], [2], [3]. Cervical insufficiency or incompetence, on the other hand, is one of the most common causes of PTB, in which many etiological factors play a role. The diagnosis is usually based on the medical history, gynecological or sonographic examinations [4].

Cervical cerclage is a common surgical procedure to keep the cervix closed and prevent PTB [5]. Like all surgical procedures, cervical cerclage is an invasive procedure that requires anesthesia and is associated with potential complications such as premature rupture of membranes, cervical injury, bleeding, infection, pregnancy loss and even the formation of a vesicovaginal fistula [6]. Alternatively, vaginal progesterone has been also recommended for the prevention of PTB in singleton pregnancies [7], 8].

On the other hand, cervical pessaries are designed and approved for the prolongation of pregnancy in patients with a short cervix, as determined by gestational age-specific centiles of cervical length (CL), and/or an overstretched uterus, as in multiple pregnancies and polyhydramnios, as well as in patients with placenta previa to stabilize the cervix [9]. Furthermore, insertion of an Arabin cervical pessary to prevent PTB is a simple, effective and non-invasive alternative that does not require medication, surgery or anesthesia, with acceptable complications such as increased vaginal discharge, pelvic discomfort and expulsion of the pessary [10]. However, in the years since the introduction of the cervical pessary in the 1950s, studies on the effectiveness of the pessary in preventing PTB have produced conflicting results, with most showing that the pessary is as effective as other prevention methods [11], [12], [13], [14], [15]. However, the traditional technique of cervical pessary insertion, in which the pessary is inserted directly into the upper vagina, does not seem to be able to fulfill its task completely. On the other hand, although treatment with the pessary is apparently simple, there is a confidence and learning curve. In this context, there are some studies that emphasize the importance of the learning curve, proper application technique and appropriate management to achieve significant improvements in the prevention of PTB [16], [17], [18]. França et al. reported that a learning curve of at least 30 applications was necessary to prevent PTB effectively enough [17]. On this basis, we hypothesized that our new technique, in which the pessary can be placed more firmly around the cervix, could be more effective than the traditional method in preventing PTB in women with cervical insufficiency. Therefore, in this context, we aimed to investigate the feasibility, efficacy and safety of our new technique for cervical pessary placement by describing our new technique and comparing the results with the traditional method.

Subjects and methods

Steps of the procedure

Once written consent for the procedure has been obtained, the woman is placed in the lithotomy position and the cervix is examined with a speculum to determine the optimal pessary size. A pair of ring forceps are passed through the central hole of the pessary, with the curvature of the pessary facing upwards (Figure 1). The vaginal entrance is opened and the cervix is exposed with the help of two vaginal retractors. The upper and lower cervical lips are carefully grasped with the ring forceps, which are already inserted through the center hole of the pessary. The pessary is pushed forward over the shafts of the ring forceps into the vagina and placed firmly around the cervix (Figure 2). Finally, the forceps are removed.

Figure 1:

Two ring forceps are inserted through the pessary ring with the curvature of the pessary facing upwards.

Figure 2:

The pessary is pushed forward over the shafts of the ring forceps into the vagina and placed firmly around the cervix.

After insertion of the pessary (for both techniques), the patient is observed for a few hours for uterine contractions, pain, vaginal bleeding or rupture of the membranes. After 48 h, a vaginal examination with transvaginal sonography is performed to check the position of the pessary, and follow-up examinations were then carried out every three weeks. The intervals between examinations, the need for hospitalization and/or additional treatment were determined individually and modified depending on the severity of the condition, e.g., in the case of an imminent PTB. The pessary should remain in place until the 37th WG, unless it has to be removed for another indication. Premature removal was performed in cases of persistent, tocolysis-resistant uterine contractions, active vaginal bleeding, severe discomfort or a desire to discontinue the procedure. In the case of a pessary that was stuck around the cervix due to cervical oedema or uterine contractions, the pessary was removed by cutting one side so as not to injure the patient. The patients were cared for by the same perinatologist for the entire duration of their pessary treatment.

Results

During the study period, 82 women were identified for data collection. However, 14 of these women were excluded. Finally, a total of 68 eligible participants, 39 of whom were treated with the traditional insertion technique (group 1) and 29 with new insertion technique (group 2), were included in the study (Figure 3).

Figure 3:

Flow diagram of the study groups.

A comparison of baseline characteristics and clinical variables of the study population was summarized in Table 1. A further comparison of the clinical characteristics at the time of application as well as the perinatal and birth-related characteristics between the two groups is shown in Table 2. There were no statistically significant differences in mode of delivery (p=0.644). The median gestational age at pessary application was significantly higher in group 1 (p=0.019) and the median time between pessary application and delivery was significantly longer in group 2 (p<0.001). Besides, median gestational age at delivery, birthweight, APGAR-1 and -5 scores and women’s satisfaction with the method were higher (p=0.011, 0.043, 0.010, 0.009 and 0.042, respectively) while the median numbers of PTB before 34 and 37 WG were lower in group 2 (p=0.020 and 0.014, respectively). In addition, concomitant use of vaginal progesterone was significantly more frequent in group 1 (p=0.005). A total of six perinatal deaths due to extreme prematurity occurred in both groups [5 (12.8 %) vs. 1 (3.4 %) in groups 1 and 2, respectively; p=0.229]. Newborns with a birthweight >2,500 g accounted for 82.8 % of all births in group 2, while this rate was 41 % in group 1, representing a significant difference between the two groups (p=0.001). However, the rate of newborns with a birthweight between 1,500 and 2,500 g was significantly higher in group 1, while no significant difference was found for a birthweight <1,500 g (p=0.010 and 0.229, respectively) (Table 3).

In the binary logistic regression analysis, the use of the traditional method was identified as an independent risk factor for delivery before 34 WG [odds ratio (OR) =5.42, 95 % confidence interval (CI) 1.393–21.064, p=0.015 and before 37 WG (OR=3.97, 95 % CI 1.426–11.040, p=0.008)]. The traditional method was also found to be an independent risk factor for delivery before 34 WG (OR=5.64, 95 % CI 1.387–22.939, p=0.016) and before 37 WG (OR=9.42, 95 % CI 2.187–40.632, p=0.003) when patients were adjusted for age, BMI, multiparity, a history of ≥2 s trimester losses, a history of PTB <28 WG and CL between the 5th–10th centiles. Using our new technique for inserting a cervical pessary resulted in 5.42- and 3.97-fold protection (and even 5.64 and 9.42-fold protection after the above adjustment) against PTB before 34 and 37 WG, respectively. CL between the 5th–10th centiles was another independent risk factor only for delivery before 37 WG (OR=11.20, 95 % CI 2.299–54.562, p=0.003), while age, BMI, multiparity, a history of ≥2 s trimester losses and/or PTB <28 WG were not independent risk factors for delivery before both 34 and 37 WG.

Discussion

The main results of our study were: (1) The rate of spontaneous PTB before 34 WG as the primary outcome was significantly lower in the new technique group. (2) Birthweight, APGAR-1 and -5 scores and women’s satisfaction with the method were significantly higher, while PTB before 37 WG was significantly lower in the new technique group. (3) Concomitant use of vaginal progesterone was required more frequently in the group using the traditional method. (4) Traditional method was identified as an independent factor for delivery before 34 and 37 WG.

In both halves of the study, the indications, treatment strategy and adherence to the current IFU of Arabin pessary were the same, and both periods involved qualified and audited implementers who had the same level of expertise in the use of cervical pessaries in patients at high risk of PTB. In the second half, all pessaries were inserted using either the new or the traditional method by the same perinatologist who had pioneered the new technique. Increasing experience may have contributed to the better results with the new method. However, this contribution affected the results of both methods equally, as the inventor who carried out both methods was the same in the second half. The contribution of increasing practical experience to better results is therefore undeniable, but the most important contribution was made by the new technique.

The use of the cervical pessary for the prevention of PTB has always been controversial, as some studies have shown a benefit [22], 23], while others have not [23], [24], [25], [26]. However, the conflicting results could be related to various factors, such as the use of different CL cut-offs for increased risk of PTB, the presence of obstetricians who were not adequately trained in the use of the pessary, and the different designs of the studies. As Kyvernitakis et al. emphasized in their integrity meta-analysis focusing on compliance with the European Medical Device Regulation, varying compliance with IFUs and a learning curve can influence the effectiveness of the pessary and thus the results [27]. This meta-analysis also reported that a significant number of pessary implementers are still not sufficiently aware of the importance of ensuring that medical devices are used in accordance with the IFU, so that serious legal consequences may be unavoidable [27].

In addition, a recent randomized controlled trial has shown that cerclage, cervical pessary and vaginal progesterone reduce PTB equally when used for the indication of a short cervix. This emphasizes that the effectiveness of the pessary is closely related to its use according to the indications stated in the IFU [28]. The results of this study can be used as a counseling tool for clinicians in the management of women with a short cervix. On the other hand, Seravalli et al. pointed out the importance of having a previous episode of threatened preterm labor in the current pregnancy, another condition that should be considered in patients in whom pessary treatment is planned due to cervical shortening [29]. They found that the use of pessaries in women with a short cervix after an episode of threatened preterm labor was less effective than in women with an asymptomatic cervical shortening.

The insertion of a cervical pessary is an affordable, safe and non-invasive method for the prevention of PTB that has been used for over two decades [30]. Although the mechanisms that counteract cervical insufficiency are not clearly known, the pessaries act as a lever that pushes back the cervical canal, which is already centralized by cervical insufficiency. Much of the pressure exerted on the cervical canal by the pregnancy itself is therefore directed towards the anterior lower uterine segment [30]. Another proposed mechanism is that the pessary ensures the integrity of the mucus plug and maintains the immunological barrier against ascending infections, thus contributing to the suppression of labor-inducing inflammation and associated processes [22], 31]. Once the pessary is inserted using our new technique, the above-mentioned mechanisms for preventing PTB can potentially become much more effective and better stabilization of the cervical canal length can be achieved through perfect positioning. Therefore, this technique can also be an alternative for physicians who are not confident with purely digital insertion.

It is an indisputable fact that in women with cervical insufficiency who have cervical changes, especially advanced cervical effacement and/or painless dilatation, the insertion of a cervical pessary using the traditional method can be difficult and is usually ineffective. However, in cases with cervical dilatation to a certain degree (e.g., less than 1–2 cm) without advanced effacement, correct placement may also be feasible using our new technique, in which the pessary is placed under the guidance of the forceps grasping the cervical lips.

Cervical pessary has an acceptable range of side effects. In a questionnaire study examining the impact of cervical pessary use during pregnancy on daily life, data such as perceived discomfort, side effects and pain during removal, and fulfillment of patients’ expectations of treatment were analyzed using numerical rating scales from 0 to 10, and most women reported an overall positive experience. The level of patient satisfaction was high and only one participant (0.6 %) had to be removed prematurely due to discomfort [32]. As vaginal discharge is the most frequently reported side effect, women should be informed before using the pessary. However, it should also be mentioned that this vaginal discharge does not always mean an infection, unless an infection is detected by vaginal culture [32].

In our study, despite the potential pain sensation during grasping of the cervical lips with ring forceps, patient satisfaction with the new method was higher than with the traditional method in which no additional instrumentation was required. This could be due to the fact that a significant proportion of births in the traditional technique group occurred at lower gestational ages than in the new technique group and therefore a negative experience related to the premature birth could also have influenced the reported experiences of some women. As pessary stabilization with our new technique is potentially much more effective than the traditional method, concomitant vaginal progesterone therapy was less preferred in group 2. It is also likely that the less frequent use of vaginal progesterone influenced the higher satisfaction with the method in group 2, as vaginal progesterone is an independent risk factor for vaginal discharge.

As far as we know, this is the first study to propose a new technique for inserting a cervical pessary as an alternative to the traditional method. Major strength of this study is that it was conducted in a large tertiary reference hospital that uses the same algorithms for diagnosis, treatment and follow-up. However, our study has some limitations, mainly due to its retrospective nature, the relatively small sample size and the lack of a control group. Although the results may not be representative of the entire population of interest due to the relatively small sample size, as previously mentioned, the present study describes a novel technique that has never been performed before. In addition, the significantly higher rates of concomitant progesterone use in the traditional method group may have underestimated the success of the new technique. On the other hand, the fact that the new technique was used at a time when clinicians, and in particular the perinatologist who introduced the new technique, were more experienced may have led to some bias in success rates. Moreover, the definition of satisfaction with the method was not specific enough, as it was defined with a general satisfaction and the positive consideration of offering the method to someone else. Satisfaction with the method should be evaluated with a Likert scale and defined more objectively. On the other hand, despite the retrospective nature of the study, there were no between-group imbalances in baseline variables, including maternal age, BMI, nulliparity, parity. Furthermore, as the cases in which PTB or termination of pregnancy was indicated and the women who discontinued the method were not included in the analysis, any associated bias in the results could also be excluded.

In conclusion, the preliminary results of our study suggest that our new technique of pessary placement may be more effective in preventing PTB, especially in women with a short or soft cervix, as it allows the pessary to be inserted higher than with digital procedure alone. Further prospective, randomized, controlled trials with larger sample sizes comparing our forceps-guided technique with the traditional method are needed to better demonstrate the efficacy and limitations.