Influence of cervical balloon fluid volume on maternal labor process, maternal and infant outcomes, and pregnancy-related anxiety

Abstract

BACKGROUND

The full implementation of the national two-child policy has presented significant challenges in ensuring the safety of pregnant women.

AIM

To investigate the effect of cervical balloon fluid volume on maternal processes, maternal and infant outcomes, and anxiety during pregnancy.

METHODS

A total of 100 singleton term pregnancies with cervical maturity induction and anxiety were selected using a lottery method; 50 women were included. Cervical balloons were used for all participants. In the control group, 80 mL of fluid was injected into both balloons; in the observation group, 80 and 100 mL were injected into the vaginal and cervical balloons, respectively. The two groups were compared for cervical maturity, labor duration, anxiety, maternal and infant outcomes, and effects on cervical ripening.

RESULTS

After treatment, the cervical maturity test (Bishop) score was significantly higher in the observation group (9.76 ± 1.19) than in the control group (7.62 ± 0.83), and the Hamilton Anxiety Scale score was lower in the observation group (7.32 ± 0.85) than in the control group (13.05 ± 1.12). The observation group showed higher rates of natural delivery and lower rates of cesarean section than the control group. The first and total stages of labor were shorter in the observation than in the control group; no significant differences were found in the second and third stages. The incidence of complications was lower in the observation group [1 (2.00%) vs 9 (18.00%) for complications; 49 (98.00%) vs 41 (82.00%) for non-complications].

CONCLUSION

The selected fluid volumes to promote cervical maturity and induce labor stabilize maternal mood, increase the natural delivery rate, shorten labor, and improve maternal and infant outcomes.

Key Words: Cervical balloon fluid volume; Singleton pregnancy; Cervical ripening; Anxiety state; Maternal labor process

Core Tip: Cervical maturity is an important factor in determining the success of labor induction and is crucial for improving the success rate of labor induction and shortening the time from labor induction to delivery.

INTRODUCTION

Full-term labor induction involves the use of artificial methods to stimulate uterine contractions and facilitate the delivery of the fetus through the vagina, with the primary aim of protecting both the mother and fetus from further harm. Promoting cervical maturity refers to the use of drugs or mechanical methods to soften, efface, and dilate the cervix prior to labor induction, increasing the likelihood of a successful vaginal delivery. The success of labor induction primarily depends on the maturity of the cervix[1,2]. Research has shown that[3] maternal prenatal anxiety can affect up to 27% of pregnant women. Anxiety can lead to increased sympathetic activity, uterine vasoconstriction, reduced uterine blood flow, and fetal hypoxia. It may also cause weak contractions, slow cervical dilation, and labor stall, all of which can seriously compromise the safety of both mother and child. Methods to promote cervical maturity include cervical cerclage, misoprostol induction, cervical balloons, prostaglandin E2 induction, and cervical water sac injection, with the cervical balloon being a commonly used method in clinical practice. The cervical balloon is a midwifery device in which 80 mL of normal saline is injected into each balloon. Through mechanical stimulation that mimics the pressure of the fetal head, the device compresses the cervix, helping to soften and dilate it[4]. However, as cervical balloons are used more frequently in clinical practice, some women exhibit poor cervical response after balloon removal. As a result, some researchers have suggested that[5] increasing the volume of fluid in the cervical balloon improves cervical softening and dilation; however, there are few clinical reports on this approach at present.

The Bishop score is commonly used to assess cervical readiness for labor. A higher Bishop score is associated with more favorable labor outcomes, making it a crucial metric for evaluating the success of cervical ripening interventions. By recording the duration of labor and monitoring any adverse maternal or neonatal outcomes, we can assess the overall impact of the cervical balloon on the labor process. Shorter labor duration and fewer complications indicate the potential of the device to enhance the birthing experience. These indicators are essential for a comprehensive evaluation of the cervical balloon’s performance, ensuring that it not only facilitates cervical ripening but is also safe and beneficial for both mother and infant. These measures contribute to the body of evidence supporting best practices in obstetrics. This paper aims to explore the effect of cervical balloon fluid volume on cervical maturity induction, maternal and infant outcomes, and anxiety in singleton term pregnancies, with the findings presented here.

MATERIALS AND METHODS

General information

A total of 100 singleton term pregnancies with cervical maturity induction and anxiety admitted to Wuxi People's Hospital between January 2023 and January 2024, were selected using a lottery method as the basis for the group, and 50 cases were chosen. The inclusion criteria were as follows: (1) Meeting the diagnostic criteria for promoting cervical ripening and labor induction in late pregnancy[6]; (2) Singleton pregnancy; and (3) Signed informed consent. The exclusion criteria were: (1) Cervical Bishop score of 6; (2) Presence of genital tract infections, such as vaginitis or cervicitis; or (3) Presence of gestational hypertension or diabetes.

Specific operation

To ensure the procedure's reproducibility and safety, detailed descriptions of the key operational details are provided below.

Disinfection is vital for preventing infection: The disinfection range covered the entire perineal area, from the mons pubis to the anal verge, and laterally to the inner thighs. A suitable antiseptic solution (e.g., povidone-iodine) was applied systematically, starting from the sterile area (i.e., the introitus) and moving outward.

Positioning of the cervical clamp: The position of the cervical clamp was determined through visual inspection and palpation. The clamp was positioned at the 3 and 9 o'clock positions of the cervix to ensure symmetrical placement and avoid excessive pressure on the cervical tissue. The clamp was applied gently and periodically checked to ensure it remained in the correct position throughout the procedure.

Placement of cervical balloon: (1) Control group: 80 mL of normal saline was injected into each of the two balloons; and (2) Observation group: 20 mL of normal saline was injected into the uterine balloon (marked with a red letter “U” at the end). The catheter was then gently withdrawn until the balloon was near the cervical os. Another 20 mL of saline was injected into the vaginal balloon (marked with a green letter “V” at the end). The fluid volume in the balloons was gradually increased (20 mL at a time) until the vaginal balloon contained 80 mL and the cervical balloon, 100 mL. The balloons were left in place for 12 hours before removal, ensuring no leakage or discomfort.

Ensuring safety and stability during balloon placement: (1) Preplacement check: Ensure the patient is in a comfortable and appropriate position (e.g., lithotomy position). Perform a final check of the equipment to ensure the balloon is intact and defect-free; (2) Gentle insertion: The catheter was inserted gently and slowly with lubricant if necessary to minimize discomfort and reduce the risk of trauma. Steady pressure was applied to advance the catheter until the balloons reached the desired position; (3) Periodic monitoring: Once in place, the patient was monitored regularly for signs of discomfort, bleeding, or other complications. The balloon position and catheter integrity were checked to ensure security and functionality; and (4) Postplacement care: After balloon placement, clear instructions were given to the patient about what to expect and how to report any concerns. Ensured the patient’s comfort and kept the area clean and dry to prevent infection.

Volume of cervical balloon fluid in both groups

In the control group, 80 mL of liquid was injected into the two balloons. In the observation group, 20 mL of saline was injected into the uterine balloon (marked with a red letter “U”), and the catheter was withdrawn outward until the uterine balloon was near the cervical opening. Then, 20 mL of saline was injected into the vaginal balloon (marked with a green letter “V”). The fluid volume in the balloons was gradually increased (20 mL at a time) until the vaginal balloon contained 80 mL and the cervical balloon contained 100 mL. Both groups were left for 12 hours before removal.

Observing indicators

Cervical ripeness: Maternal cervical maturity was evaluated using the cervical maturity test (Bishop score)[7]. The score consists of five aspects, with a maximum score of 13. A score of 4-6 points has a 50% success rate, 7-9 points has an 80% success rate, and > 9 points indicates a successful trial birth. The duration of labor and any adverse maternal or neonatal outcomes were recorded.

Anxiety: The Hamilton Anxiety Scale (HAMA)[8] was used to assess anxiety levels. Asymptomatic, mild, moderate, severe, and extreme anxiety were classified as < 7, 8-14, 14-21, and > 21, respectively.

Promotion of cervical ripening effect: Judged using the Cervical Bishop score. The effectiveness was categorized as effective (increase > 3 points), moderately effective (increase of 1-3 points), and ineffective (no increase). The total effective rate was calculated as 1 minus the ineffective rate.

Statistical analysis

The data were processed using Statistical Package for Social Sciences 22.0. Count data are represented as [n (%)], and the χ² test was used (with corrected χ² when n > 40 and 1 < 5). Measurement data are expressed as (mean ± SD), and t-tests were performed. A P value < 0.05 indicated statistical significance.

RESULTS

General data of the study subjects

The control group had ages ranging from 24 to 33 years, with a mean age of 28.51 ± 2.42 years, and gestational weeks ranging from 37 to 42, with a mean of 39.51 ± 0.76 weeks. There were 28 and 22 cases in each respective subgroup. The observation group had ages ranging from 24 to 33 years, with a mean age of 28.54 ± 2.40 years, and gestational weeks ranging from 37 to 42, with a mean of 39.53 ± 0.79 weeks. The observation group consisted of 23 and 27 cases, respectively. There were no significant differences between the groups (P > 0.05).

Pre- and posterior cervical maturity between the two groups

Before treatment, no significant difference was observed between the two groups (P > 0.05). After treatment, the score increased in both groups and was higher in the observation group (P < 0.05; Table 1).

Table 1 Comparison of cervical maturity in the two groups (mean ± SD, score).

Group	Case	Pretherapy	Post-treatment	t’	P value
Control	50	2.87 ± 0.47	7.62 ± 0.83	35.213	< 0.001
Observation	50	2.89 ± 0.48	9.76 ± 1.19	37.858	< 0.001
t		0.211	10.430
P value		0.834	< 0.001

Comparison of maternal delivery mode between the two groups

The number of cesarean sections and vaginal deliveries in the control group was higher than that in the intervention group, the number of natural deliveries was lower than that in the intervention group, and the two groups were significantly different (P < 0.05; Table 2).

Table 2 Comparison of maternal delivery mode between the two groups, n (%).

Group	Case	Uterine-incision delivery	Vaginal midwifery	Natural labor
Control	50	13 (26.00)	18 (36.00)	19 (38.00)
Observation	50	4 (8.00)	16 (32.00)	30 (60.00)
Z		-2.376
P value		0.017

Comparison of labor time between the two groups

The first and total stages of labor were shorter in the observation group than in the control group (P < 0.05). However, no significant difference was found in the second and third stages of labor (P > 0.05; Table 3).

Table 3 Comparison of the labor time of the two groups (mean ± SD, minute).

Group	Case	First stage of labor	Second stage of labor	Third stage of labor	Total stage of labor
Control	50	603.52 ± 47.21	49.71 ± 7.86	11.30 ± 1.39	663.05 ± 45.19
Observation	50	440.12 ± 32.25	48.73 ± 5.14	10.96 ± 1.35	496.21 ± 42.03
t		18.684	0.684	1.126	17.383
P value		< 0.001	0.496	0.264	< 0.001

Comparison of maternal anxiety before and after treatment

Before treatment, no significant difference was observed between the two groups (P > 0.05). However, after treatment, a significant difference was found (P < 0.05; Table 4).

Table 4 Comparison of anxiety in the two groups (mean ± SD, score).

Group	Case	Pretherapy	Post-treatment	t’	P value
Control	50	22.79 ± 3.10	13.05 ± 1.12	20.895	< 0.001
Observation	50	22.81 ± 3.13	7.32 ± 0.85	33.771	< 0.001
t		0.032	28.817
P value		0.974	< 0.001

Comparison of maternal and infant outcomes between the two groups

The incidence of adverse maternal and infant outcomes was lower in the observation group than in the control group (P < 0.05; Table 5).

Table 5 Comparison of maternal and infant outcomes between the two groups, n (%).

Group	Case	Excessive contractions	postpartum hemorrhage	Cervical edema	Asphyxia neonatorum	Fetal distress	Total incidence
Control	50	2 (4.00)	1 (2.00)	3 (6.00)	1 (2.00)	2 (4.00)	9 (18.00)
Observation	50	1 (2.00)	0 (0.00)	0 (0.00)	0 (0.00)	0 (0.00)	1 (2.00)
χ2							7.111
P value							0.008

Comparison of the effect of promoting cervical ripening in the two maternal groups

The observation group showed better results than the control group (P < 0.05; Table 6).

Table 6 Comparison of maternal cervical ripening efficacy in the two groups, n (%).

Group	Case	Excellence	Effective	Invalid	Total effective rate
Control	50	18 (36.00)	23 (46.00)	9 (18.00)	41 (82.00)
Observation	50	32 (64.00)	17 (34.00)	1 (2.00)	49 (98.00)
χ2					7.111
P value					0.008

DISCUSSION

Full-term labor induction involves the use of drugs or mechanical methods to stimulate maternal contractions, promote cervical softening and maturity, and facilitate vaginal delivery. Clinical studies have shown that cervical maturity is a crucial factor in determining the success of labor induction[9]. Without proper induction, the risk of complications increases, and the health and safety of both the mother and infant can be severely compromised. Consequently, enhancing the safety and clinical efficacy of cervical ripening has become a key area of research.

The results of this study indicated that the cervical Bishop score was significantly higher in the observation group (9.76 ± 1.19) than in the control group (7.62 ± 0.83) (P < 0.05). In the observation group, 49 patients (98.00%) had effective results, compared with 41 patients (82.00%) in the control group (P < 0.05). This suggests that injecting 80 and 100 mL of fluid into the vaginal and cervical balloons can enhance cervical maturity. The primary mechanism of cervical balloon ripening involves dual balloon pressure, simulating the fetal head’s effect on the cervix, accelerating cervical expansion. The injection of saline into the cervical balloon generates pressure that stimulates the synthesis and release of prostaglandins, aiding in cervical softening. The higher volume of fluid in the cervical balloon (100 mL) enhances the stimulation of the cervix, thereby improving the effect on softening and dilation. These findings align with previous studies highlighting the effectiveness of mechanical stimulation in promoting cervical ripening[10]. The observation group’s higher Bishop score suggests that increasing the fluid volume in the cervical balloon enhances the mechanical pressure on the cervix, leading to more effective softening and dilation. This is supported by international research showing that mechanical dilation techniques significantly improve cervical readiness for labor.

Regarding delivery outcomes, the observation group had a higher rate of spontaneous deliveries (60.00% vs 38.00%) and lower rates of cesarean sections and vaginal deliveries (8.00% and 32.00% vs 26.00% and 36.00%, respectively), with significant differences between the groups (P < 0.05). The observation group also had shorter first and total stages of labor than the control group (P < 0.05), while no significant differences were observed in the second and third stages (P > 0.05). These results demonstrate that injecting 80 and 100 mL of fluid into the vaginal and cervical balloons can promote natural delivery and significantly shorten labor duration. Cervical maturity is closely related to smoother delivery, and the cervical balloon functions as a double-lumen catheter that places a water sac between the uterine wall and fetal membrane, generating mechanical stimulation of the uterus and cervical canal, similar to the natural cervical ripening process[11]. This stimulation induces uterine contractions, helping the cervix dilate gradually and safely. Additionally, patients can walk freely after the balloon is inserted, which supports cervical dilation and fetal head descent while reducing the likelihood of cesarean section[12]. The injection of 80 and 100 mL of fluid into the vaginal and cervical balloons, respectively, aids in cervical dilation and facilitates fetal delivery.

In terms of maternal and infant safety, the study found a significantly lower incidence of adverse outcomes in the observation group (2.00%) than in the control group (18.00%) (P < 0.05). This indicates that injecting 80 and 100 mL of fluid into the vaginal and cervical balloons, respectively, can help ensure the safety of both mother and infant. Some researchers have suggested that cervical ripening promotes regular uterine contractions[13], thus reducing the risk of complications such as prolonged labor and dystocia, ultimately ensuring maternal and fetal safety.

Regarding maternal anxiety, the HAMA score was significantly lower in the observation group (7.32 ± 0.85) than in the control group (13.05 ± 1.12) (P < 0.05). This suggests that the injection of 80 and 100 mL of fluid into the vaginal and cervical balloons can improve the maternal psychological state. Owing to hormonal changes and concerns about fetal health, many women experience anxiety. By promoting natural delivery and ensuring the safety of both mother and baby, this intervention effectively helps alleviate anxiety and improves maternal well-being.

CONCLUSION

Injecting 80 and 100 mL of fluid into the vaginal and cervical balloons of singleton term pregnancies can promote cervical maturity and induce labor, particularly in cases with anxiety. This approach stabilizes maternal mood, improves the rate of natural delivery, shortens labor, and enhances maternal and infant outcomes. It is a well-recognized method and is highly recommended for clinical practice.