Invest Clin 65(1): 5 - 15, 2024 https://doi.org/10.54817/IC.v65n1a01

Corresponding author: Xiaorui Han. Department of Gynecology and Obstetrics, Xingtai People’s Hospital, Xingtai

045031, Hebei Province, China. Email: hanxrxph@xamy-edu.cn

Clinical effects of Cook® cervical ripening

balloon on promoting cervical dilation for

early termination of pregnancy in high-risk

parturients.

Xiaorui Han, Junnan Cai, Wei Dong and Ya Li

Department of Gynecology and Obstetrics, Xingtai People’s Hospital, Xingtai, China.

Keywords: Cook® cervical ripening balloon; cervical dilation; high-risk parturient;

termination of pregnancy.

Abstract. We aimed to evaluate the clinical effects of oxytocin, misopros-

tol, controlled-release dinoprostone suppository, and Cook® cervical ripening

balloon on early termination of pregnancy in high-risk parturients. Four hun-

dred high-risk full-term parturients not in labor who were unsuitable for await-

ing delivery and treated from May 2018 to July 2020 were divided into groups

I-IV with a random number table (n=100). They received labor induction by

oxytocin, misoprostol, controlled-release dinoprostone suppository, and Cook®

cervical ripening balloon, respectively. The general data, cervical ripening ef-

fect, delivery outcome, delivery time, adverse reactions, and neonatal condi-

tions were compared. The time from the beginning of labor induction to labor

and duration of the first, third, and total stages of labor were shorter in group

II-IV than in group I (p<0.05). The incidence rates of excessive uterine contrac-

tion in groups II and III were higher than those of groups I and IV, and the inci-

dence rates of fetal distress in groups I-III exceeded that of group IV (p<0.05).

The neonatal Apgar scores of groups III and IV were higher than those of groups

I and II (p<0.05). Cook® cervical ripening can promote cervical maturation

and shorten the labor induction time and stage of labor.

6 Han et al.

Investigación Clínica 65(1): 2024

Efectos clínicos del balón de maduración cervical de Cook®

sobre la dilatación cervical para la interrupción temprana

del embarazo en las parturientas de riesgo alto.

Invest Clin 2024; 65 (1): 5 – 15

Palabras clave: balón de dilatación cervical COOK; maduracion cervical; parturientas

de alto riesgo; interrupción del embarazo.

Resumen. Nuestro objetivo fue evaluar los efectos clínicos de la oxitoci-

na, el misoprostol, el supositorio de dinoprostona de liberación controlada y

el balón de maduración cervical de Cook® en la interrupción temprana del

embarazo en parturientas de alto riesgo. Cuatrocientas parturientas a término

de alto riesgo que no estaban en trabajo de parto y que no estaban aptas para

esperar el parto y fueron tratadas desde mayo de 2018 hasta julio de 2020 se

dividieron en grupos I-IV con una tabla de números aleatorios (n = 100). Reci-

bieron inducción del trabajo de parto con oxitocina, misoprostol, supositorio

de dinoprostona de liberación controlada y balón de maduración cervical de

Cook®, respectivamente. Se compararon los datos generales, efecto de ma-

duración cervical, resultado del parto, tiempo de parto, reacciones adversas y

condiciones neonatales. El tiempo desde el inicio de la inducción del trabajo

de parto hasta el parto y la duración de la primera etapa, tercera etapa y etapa

total del trabajo de parto fueron más cortos en el grupo II-IV que en el grupo I

(p<0,05). Las tasas de incidencia de contracción uterina excesiva en el grupo

II y III fueron más altas que las del grupo I y IV, y las tasas de incidencia de

sufrimiento fetal en el grupo I-III excedieron las del grupo IV (p<0,05). Las

puntuaciones de Apgar neonatal del grupo III y IV fueron más altas que las del

grupo I y II (p<0,05). El globo de maduración cervical de Cook® puede pro-

mover la maduración cervical, acortar el tiempo de inducción del parto y las

etapas del parto.

Received: 06-11-2022 Accepted: 26-09-2023

INTRODUCTION

Social development and lifestyle chang-

es have made high-risk complications more

commonly seen, such as gestational hyper-

tension, diabetes, oligohydramnios, and pro-

longed pregnancy, which may endanger ma-

ternal and infant health. Induction of labor

serves as a frequently used clinical method

for managing high-risk pregnancies. It in-

volves the adoption of manual interventions

to stimulate uterine contractions and assist

in early vaginal delivery before natural labor

starts. Clinical experience has shown that

the success of induced labor is closely cor-

related with the degree of cervical maturity

and that induction of labor when the cervix is

immature can lead to a prolonged labor pro-

cess, fetal distress, and even failed induced

labor, significantly increasing the risk of ce-

sarean section in parturients 1. According to

the data, the failure rate of induced labor is

Early termination of pregnancy for high-risk parturients 7

Vol. 65(1): 5 - 15, 2024

increased by six times, and the risk rate of

cesarean section can be increased twice in

parturients whose cervical Bishop score is

below 3 points compared with those in par-

turients with a cervical Bishop score above

3 points, revealing that promoting cervical

maturation is necessary for successful in-

duced labor and natural delivery of parturi-

ents 2. Currently, there are several clinical

approaches to promote cervical maturation

and induction of labor. Although there is

extensive clinical experience in medication

methods, individual differences make it

challenging to fully guarantee efficacy and

safety 3. The Cook® cervical ripening bal-

loon has been widely applied in clinical prac-

tice abroad, but it is still in the promotion

stage in China. It certainly causes no adverse

reactions and can stimulate the cervix me-

chanically and generate pressure, thereby

promoting cervical maturation and inducing

labor 4. However, there has been no optimal

plan yet. Therefore, 400 high-risk full-term

parturients not in labor who were not suit-

able for awaiting delivery and treated in

our hospital were selected in this study, and

the clinical effects of oxytocin, misoprostol,

controlled-release dinoprostone suppository,

and Cook® cervical ripening balloon were

explored, aiming to provide a solid basis to

clinical application.

MATERIAL AND METHODS

General data

Four hundred high-risk full-term partu-

rients not in labor who were unsuitable for

awaiting delivery and treated in our hospital

from May 2018 to July 2020 were selected

and divided into groups I-IV (n=100) using

a random number table. Inclusion criteria

were as follows: 1) primiparae aged 20-35

years old, 2) those with singleton pregnancy

in cephalic presentation and gestational age

of 37-42 weeks, 3) those without contrain-

dications to induced labor and vaginal trial

labor, 4) those with a cervical Bishop score

<6 points, 5) those with indications for in-

duced labor in the third trimester, including

gestational diabetes mellitus, gestational

hypertension and intrahepatic cholestasis of

pregnancy, and those with oligohydramnios,

delayed pregnancy and fetal growth restric-

tion that could be tolerated, 6) those with

complete clinical examination data, and 7)

those whom or whose families signed the in-

formed consent. Exclusion criteria were as

follows: 1) parturients complicated with se-

vere dysfunction of the heart, liver, or kidney,

2) those unable to cooperate in the study

due to mental disorders, or 3) those with

bleeding in the third trimester or a history

of uterine surgery. This study was reviewed

and approved by our hospital’s Medical Eth-

ics Committee.

METHODS

All parturients underwent detailed

prenatal examinations, the vital signs of

parturients and fetuses were monitored in

real-time, and prenatal guidance and psy-

chological comfort were given.

Oxytocin (NMPN: H31020850, Shang-

hai Harvest Pharmaceutical Co., Ltd.) was

given to group I. 2.5 U of oxytocin added into

500 mL of normal saline was intravenously

infused at 8 drops/min at first. The infusion

speed was adjusted if no uterine contraction

occurred, 40 drops/min at most. Intrave-

nous infusion lasted 8-12 h a day until effec-

tive uterine contraction occurred, i.e., uter-

ine contraction three times within 10 min,

more than 30 s per time. Cervical Bishop

score was given to the parturients still not

in labor after infusion with 2.5 U of oxytocin

or regular uterine contraction for more than

6-8 h. Those with a cervical Bishop score

<6 points continued to receive labor induc-

tion by oxytocin in the same way the next

day. Those with a cervical Bishop score ≥6

points continued to receive labor induction

by oxytocin if there was no effective uterine

contraction with normal amniotic fluid one

hour after the artificial rupture of the fetal

membrane. If the parturients still failed to

8 Han et al.

Investigación Clínica 65(1): 2024

enter the stage of labor at 3 d, the induced

labor was deemed a failure, and they were

converted to cesarean delivery.

Misoprostol (NMPN: H20000668, Bei-

jing Zizhu Pharmaceutical Co., Ltd.) was ap-

plied to group II. After routine vaginal and

vulvar sterilization, 25 μg of misoprostol was

placed at the posterior fornix of the vagina,

and the parturients were instructed to rest

in bed. After 30 min, the uterine contrac-

tion was observed, and the fetal heart rate

was monitored. If there was still no uterine

contraction after six hours, misoprostol was

applied once again, and the total dose was

50 μg at most within 24 h. Once persistent

uterine contractions occurred, misoprostol

was immediately taken out. The fetal mem-

brane was artificially ruptured for the par-

turients with a cervical Bishop score >6

points. Oxytocin was also used if there was

no effective uterine contraction with normal

amniotic fluid after one hour. If the parturi-

ents still failed to give birth at 3 d, induced

labor was considered a failure, and they were

converted to cesarean delivery.

A controlled-release dinoprostone

suppository (trade name: Propess, model

MA09P01B, CTS, UK) was used in group III.

After routine vaginal and vulvar sterilization,

one 0.8 mm controlled-release dinoprostone

suppository was placed at the posterior for-

nix of the vagina and rotated 90°, and the

termination tape was rolled up and packed

into the vaginal orifice. Then, the partici-

pants were instructed to rest in bed for 30

minutes, during which the fetal heart rate

was monitored. If indications for labor were

found, and uterine tetanic contraction or

hyperstimulation, fetal distress, rupture of

membranes, tachycardia, hypotension, nau-

sea, and vomiting, or other severe adverse

reactions occurred, the controlled-release

dinoprostone suppository was taken out, and

its placement time was 12 hours at most. The

fetal membrane was artificially ruptured for

the parturients with a cervical Bishop score

>6 points. Oxytocin was also used if there

was no effective uterine contraction with

normal amniotic fluid after one hour. If the

parturients still failed to give birth at 3 d,

induced labor was considered a failure, and

they were converted to cesarean delivery.

The Cook® cervical ripening balloon

(model J-CRB-184000, Cook, USA) was used

in group IV. After it was confirmed that relat-

ed examination results were normal and the

oxytocin challenge test result was negative,

the bladder was emptied, the parturients lay

in a lithotomy position, the vulva, vagina,

and cervix were sterilized, and a speculum

was placed to expose the cervix fully. Then,

the Cook® cervical ripening balloon was

placed into the uterine cavity, with both

balloons entering the cervical canal. 40 mL

of normal saline was injected from the red

tube marked by U to fill the uterine balloon.

The uterine balloon was pulled backward to

make it cling closely to the cervix. Besides,

20 mL of normal saline was injected from

the green tube marked by V to fill the vagi-

nal balloon in the outer cervix. After that,

the speculum was withdrawn, the balloons

were placed on both sides of the cervix, and

normal saline (80 mL at most) was injected

into each balloon. The tail end of the bal-

loon was fixed on the inner thigh, followed

by timing. The uterine contraction and fe-

tal heart rate were monitored. When there

was vaginal discharge or persistent uterine

contraction, the balloon was withdrawn, or it

was removed after 12 h. The fetal membrane

was artificially ruptured for the parturients

with a cervical Bishop score >6 points, and

the uterine contraction and character of am-

niotic fluid were closely monitored. If there

was no effective uterine contraction with

normal amniotic fluid after one hour, oxyto-

cin was used until the uterine orifice opened

3 cm. The parturients with a cervical Bishop

score <6 points continued to receive labor

induction by oxytocin. If they still failed to

enter the stage of labor at 3 d, the induced

labor was deemed a failure, and they were

converted to cesarean delivery.

Early termination of pregnancy for high-risk parturients 9

Vol. 65(1): 5 - 15, 2024

Observation indices

The basic data of parturients, cervical

ripening effect, delivery outcome, delivery

time, adverse reactions, neonatal Apgar

score, and body weight in each group were

recorded.

Before and at 12 h after intervention in

induced labor, the cervical ripening effect

was assessed according to the cervical Bish-

op score, including five indices (position of

uterine orifice, the openness of uterine ori-

fice, cervical stiffness, cervical canal regres-

sion, and presentation position). The total

score is 13 points, in which 10-13 points,

7-9 points, 4-6 points, and 0-3 points indi-

cate a success rate of spontaneous labor of

nearly 100%, 80%, about 50%, and failure

of artificial rupture of fetal membrane, re-

spectively. The effectiveness evaluation cri-

teria were markedly effective: in labor or

an increase in the cervical Bishop score by

3 points or more. Effective: an increase in

the cervical Bishop score by 2 points. Inef-

fective: an increase in the cervical Bishop

score by less than 2 points. Total effective

rate = (markedly effective cases + effective

cases)/total cases × 100%.

Neonatal Apgar score was given at 5

min after birth. Regarding skin color, red-

ness of systemic skin and mucosa, redness

of body and blue-violet color of four limbs,

and blue-violet or pale color of the whole

body were scored 2 points, 1 point, and 0

point, respectively. Regarding heart rate,

>100 beats/min, <100 beats/min, and no

heartbeat after birth were scored 2 points,

1 point, and 0 point, respectively. Regard-

ing response, 2 points, 1 point, and 0 points

were given to normal response after birth,

slight movement, and no response, respec-

tively. As for muscular tension, 2 points, 1

point, and 0 points were given to free move-

ment of four limbs, slight flexion of four

limbs, and low muscular tension, respective-

ly. As for breathing, regular breathing after

birth, slow and irregular breathing, and no

breathing were scored 2 points, 1 point, and

0 points, respectively. The total scores of

8-10 points, 4-7 points, and 1-3 points indi-

cated normal condition, mild asphyxia, and

severe asphyxia, respectively.

Statistical analysis

IBM® SPSS 16.0 software was used

for statistical analysis. Numerical data were

expressed as n (%) and compared among

groups by the chi-square (χ2) test. Mea-

surement data were expressed as mean ±

standard deviation (x ± s) and compared

among groups by one-way variance analysis

and between two groups by independent t-

test in the case of statistical significance.

p<0.05 suggested that the difference was

statistically significant.

RESULTS

Baseline clinical data of parturients

There were no significant differences

in the parturients’ age, gestational age,

BMI, cervical Bishop score before the inter-

vention, and indications for induced labor

among groups (p>0.05) (Table 1).

Cervical ripening effects

No significant differences were found

in the cervical Bishop score and total ef-

fective rate of cervical ripening between

group I and group II and between groups

III and IV (p>0.05). The cervical Bishop

score and total effective rate of cervi-

cal ripening in group III and group IV

were higher than those in groups I and II

(p<0.05) (Table 2).

Delivery outcomes

There was no significant difference

in the delivery mode between group I and

group II and between groups III and IV

(p>0.05), but the spontaneous labor rate in

group III and group IV was higher than that

in group I and group II (p<0.05). The post-

partum blood loss was not significantly dif-

ferent among group I, group II, and group III

(p>0.05), but it was more significant than

that in group IV (p<0.05) (Table 3).

10 Han et al.

Investigación Clínica 65(1): 2024

Table 1

Baseline clinical data of parturients.

ouGrop n Age

(year,

x ± s)

Gestational age

(week,

x ± s)

BMI

(kg/m2,

x ± s)

Cervical

Bishop score

(point,

x ± s)

Indication for induced labor [n (%)]

Prolonged

pregnancy

Oligohy-

dramnios

Gestational

diabetes

mellitus

Gestational

hypertension

Group oup I 100 28.55±4.05 39.55±1.71 28.57±2.86 2.96±1.43 43 (43.00) 34 (34.00) 16 (16.00) 7 (7.00)

Group II 100 27.56±3.41 39.48±1.79 29.11±2.83 2.85±1.40 39 (39.00) 36 (36.00) 15 (15.00) 10 (10.00)

Group III 100 28.25±3.17 39.51±1.66 28.92±2.93 3.12±1.46 42 (42.00) 35 (35.00) 15 (15.00) 8 (8.00)

Group IV 100 28.21±3.49 39.51±1.76 28.42±3.02 2.76±1.33 40 (40.00) 38 (38.00) 16 (16.00) 6 (6.00)

F/χ2 0.819 0.263 1.294 1.586 1.682

P 0.354 0.708 0.116 0.215 0.996

The count data were expressed as n (%), and compared among multiple groups by the chi-square (χ2) test. The measurement data were expressed as mean ±

standard deviation (x ± SD) and compared among multiple groups by one-way analysis of variance (F value). p values indicated the differences among multiple

groups.

Table 2

Cervical ripening effects.

Group n

Cervical Bishop

score

(point, x ± s)

Cervical ripening effect [n (%)] Total effective rate

(%)

Markedly effective Effective Ineffective

Group I 100 5.36±1.67 29 (29.00) 36 (36.00) 35 (35.00) 65.00

Group II 100 5.54±1.71 32 (32.00) 35 (35.00) 33 (33.00) 67.00

Group III 100 6.79±1.49ab 53 (53.00) 34 (34.00) 13 (13.00) 87.00ab

Group IV 100 6.85±1.74ab 57 (57.00) 35 (35.00) 8 (8.00) 92.00ab

F/χ25.672 39.862 32.761

p <0.001 <0.001 <0.001

The count data were expressed as n (%), and compared among multiple groups by the chi-square (χ2) test. The measurement data

were expressed as mean ± standard deviation (x ± SD) and compared among multiple groups by one-way analysis of variance (F

value). a p<0.05 vs. group I, b p<0.05 vs. group II.

Early termination of pregnancy for high-risk parturients 11

Vol. 65(1): 5 - 15, 2024

Delivery time

There was no significant difference in

the duration of the second stage of labor

among groups (p>0.05). The time from the

beginning of labor induction to labor and the

duration of the first, third, and total stage of

labor had no significant differences among

group II, group III, and group IV (p>0.05),

but they were all shorter than those in group

I (p<0.05) (Table 4).

Adverse reactions

The incidence rates of amniotic fluid

pollution, laceration of the birth canal, in-

trauterine infection, and postpartum hemor-

rhage had no significant differences among

groups (p>0.05). Group II and Group III had

a higher incidence rate of excessive uterine

contraction than Group I and Group IV, and

Group I, Group II, and Group III had a high-

er incidence rate of fetal distress than Group

IV (p<0.05) (Table 5).

Neonatal conditions

There was no significant difference in

the neonatal birth weight among groups

(p>0.05). The neonatal Apgar score was

higher in Group III and Group IV than that

in Groups I and II (p<0.05) (Table 6).

DISCUSSION

The degree of cervical maturity is a

critical factor in determining the success of

induced labor. According to data, induced

labor can be successful among parturients

with a cervical Bishop score ≥9 points, while

the success rate of induced labor is only 20%

among those with a cervical Bishop score of

<6 points, so measures of cervical ripening

need to be taken5. Currently, the commonly

used cervical ripening and labor induction

methods include medication (oxytocin,

misoprostol, and controlled-release dinopro-

stone suppository) and mechanical methods

(Cook® cervical ripening balloon). Daykan

et al. 6 found that the total effective rate of

cervical ripening by Propess was significantly

higher than that by misoprostol and oxyto-

cin. The success rate of cervical ripening by

the Cook® cervical ripening balloon is far

higher than that produced by a low-dose

intravenous infusion of oxytocin 7. Herein,

the cervical ripening effect was compared

among four commonly used methods of la-

bor induction, and the conclusions were con-

sistent with the above reports. Oxytocin is a

commonly used traditional drug for induced

labor, and it mainly acts on the receptors in

Table 3

Delivery outcomes.

Group n Delivery mode [n (%)] Postpartum blood loss

(mL,x ± s)

Spontaneous labor Cesarean delivery

Group I 100 63 (63.00) 37 (37.00) 236.85±24.71

Group II 100 66 (66.00) 34 (34.00) 232.49±23.59

Group III 100 85 (85.00)ab 15 (15.00)ab 238.74±24.62

Group IV 100 90 (90.00)ab 10 (10.00)ab 205.53±18.47abc

F/χ2 29.934 8.317

p <0.001 <0.001

The count data were expressed as n (%), and compared among multiple groups by the chi-square (χ2) test. The

measurement data were expressed as mean ± standard deviation (x ± SD) and compared among multiple groups

by one-way analysis of variance (F value). a p<0.05 vs. group I, b p<0.05 vs. group II, c p<0.05 vs. group III.

12 Han et al.

Investigación Clínica 65(1): 2024

Table 4

Delivery time.

Group n Time from

beginning of labor

induction to labor

(h,x ± s)

First stage

of labor

(h, x ± s)

Second stage

of labor

(h, x ± s)

Third stage

of labor

(h, x ± s)

Total stage

of labor

(h, x ± s)

Group I 63 15.41±3.76 9.52±2.37 0.42±0.15 0.20±0.07 10.34±1.09

Group II 66 12.11±2.95a 5.30±1.44a0.40±0.13 0.16±0.05a 5.92±0.96a

Group IIII 85 12.04±2.22a 5.17±1.54a0.41±0.12 0.15±0.07a 5.90±1.05a

Group IV 90 11.41±2.90a 5.18±1.36a0.39±0.15 0.15±0.06a 5.83±1.09a

F 7.326 14.238 1.324 4.753 23.542

P <0.001 <0.001 0.169 <0.001 <0.001

The measurement data were expressed as mean ± standard deviation (x ± SD) and compared among multiple

groups by one-way analysis of variance (F value). a P<0.05 vs. group I.

Table 5

Adverse reactions.

Group n Amniotic fluid

pollution

[n (%)]

Excessive

uterine

contraction

[n (%)]

Laceration of

birth canal

[n (%)]

Intrauterine

infection

[n (%)]

Fetal

distress

[n (%)]

Postpartum

hemorrhage

[n (%)]

Group I 100 4 (40.00) 2 (2.00) 8 (8.00) 2 (2.00) 14 (3.00) 3 (3.00)

Group II 100 11 (11.00) 11 (11.00)a7 (7.00) 3 (3.00) 18 (18.00) 3 (3.00)

Group III 100 10 (10.00) 12 (12.00)a9 (9.00) 3 (3.00) 13 (5.00) 4 (4.00)

Group IV 100 6 (6.00) 1 (1.00)bc 5 (5.00) 4 (4.00) 2 (2.00)abc 2 (2.00)

χ24.581 16.619 1.301 0.687 13.574 0.687

p 0.205 0.001 0.729 0.876 0.004 0.876

The count data were expressed as n (%), and compared among multiple groups by the chi-square (χ2) test. a p<0.05

vs. group I, b p<0.05 vs. group II, c p<0.05 vs. group III.

Table 6

Neonatal conditions

Group n Neonatal Apgar score

(point, x ± s)

Birth weight

(g, x ± s)

Group I 100 8.99±0.19 3299.28±239.10

Group II 100 9.02±0.18 3315.37±242.96

Group III 100 9.35±0.20ab 3286.35±231.89

Group IV 100 9.40±0.23ab 3336.34±231.10

F 7.618 1.328

p <0.001 0.125

The measurement data were expressed as mean ± standard deviation (x ± SD) and compared among multiple

groups by one-way analysis of variance (F value). a p<0.05 vs. group I, b p<0.05 vs. group II.

Early termination of pregnancy for high-risk parturients 13

Vol. 65(1): 5 - 15, 2024

decidual cells to promote the synthesis and

release of prostaglandins, stimulating and

exciting the uterine smooth muscle and in-

ducing uterine contraction. However, its re-

ceptors are widely distributed in the uterus

but less distributed in the cervix, leading to

a limited effect. Misoprostol, as a prostaglan-

din E1 preparation, enhances the effective

softening of uterine fibrous tissues and the

degradation of collagen fibrin by promot-

ing the release of a variety of proteases by

cervical connective tissues, thereby induc-

ing uterine smooth muscle contraction,

cervical dilation, and uterine muscle excite-

ment. However, it is difficult to control its

dosage, and the inaccurate dosage can not

only harm cervical ripening but also cause a

series of adverse reactions. In this study, the

spontaneous labor rate in the four groups

was in accord with the view that the degree

of cervical maturity determines the success

of labor induction and also consistent with

multiple early reports 8.

The labor time and duration of the

stage of labor of parturients in the balloon

group were significantly shortened com-

pared with those of the oxytocin group 9.

In a retrospective controlled study, the time

from drug or balloon placement to labor

and the duration of the total stage of labor

in the dinoprostone suppository group was

evidently shorter than those in the balloon

group 10. In this study, the results did not

fully agree with the above reports. The rea-

son is that the delivery time was compared

among participants receiving successful la-

bor induction so the results may be incom-

pletely consistent due to differences in sam-

ple size and research methods. However, it

is recognized clinically that labor induction

with oxytocin has a low success rate and a

long stage of labor.

In addition to the cervical ripening ef-

fect and the success rate of labor induction,

maternal-infant safety cannot be ignored.

The ideal methods of cervical ripening and

labor induction should cause no excessive

uterine contraction and damage to maternal

health and lead to no adverse reactions in

infants, such as organ damage and respira-

tory depression. It has been reported early

that the overall safety of full-term partu-

rients using oxytocin is not high, and they

often suffer from complications such as

cervical edema, intrauterine fetal distress,

and neonatal asphyxia 11. The application of

misoprostol in the vagina has a specific risk

of causing excessive uterine contraction,

meconium-stained amniotic fluid, abnormal

fetal heart rate, emergency cesarean sec-

tion, postpartum hemorrhage, and neonatal

asphyxia12. Dinoprostone suppository can re-

sult in persistent and uterine solid contrac-

tion, so magnesium sulfate needs to be used

to inhibit uterine contraction and fetal dis-

tress can be caused in severe cases, in which

case parturients need to be converted to

emergency cesarean section 13. In this study,

the misoprostol and controlled-release dino-

prostone suppository used in groups II and

III were prostaglandin E1 and E2 prepara-

tions, respectively. Multiple studies in Chi-

na and foreign countries have revealed that

the more severe adverse reaction caused by

prostaglandins in labor induction is uter-

ine hyperstimulation, and fetal distress may

even occur. In group I, oxytocin was used for

a long time, and uterine inertia also lasted

for an extended period, thus increasing the

incidence of fetal distress. In group IV, the

Cook® cervical ripening balloon had small

and mild stimulation, significantly reducing

uterine hyperstimulation, and it can even be

applied in the scarred uterus. As a result,

Groups II and III had a higher incidence rate

of excessive uterine contraction than Group

I and Group IV, and Group I, Group II, and

Group III had a higher incidence rate of fetal

distress and a more considerable postpar-

tum blood loss than Group IV. Moreover, the

neonatal Apgar score was higher in Groups

III and IV than in Groups I and II, and the

possible reason is closely related to the short

stage of labor in Groups III and IV.

Regardless, this study is limited. This

is a single-center study with a small sample

14 Han et al.

Investigación Clínica 65(1): 2024

size. Further multicenter studies with more

cases are needed to confirm our findings.

In conclusion, Cook® cervical ripening

balloons can exert an excellent effect, short-

en the duration of induced labor and stage of

labor, raise the spontaneous labor rate, and

reduce adverse maternal-infant outcomes,

worthy of clinical popularization and appli-

cation. In clinical practice, however, it is still

necessary to first check the specific position

of the placenta by ultrasound and determine

whether there is placenta previa or low-lying

placenta in parturients. The balloon should

be placed into the uterine cavity in the con-

tralateral direction of the placenta to avoid

placental abruption. The balloon should not

be placed for more than 12 hours, and cor-

responding measures should be taken later

according to the specific situation.

ACKNOWLEDGMENTS

None.

Funding

None.

Conflicts of interest

No potential conflict of interest was re-

ported by the authors.

Author ORCID number

• Xiaorui Han (XH):

0000-0002-0382-932X

• Junnan Cai (JC):

0000-0001-6042-7776

• Wei Dong (WD):

0000-0003-2301-1872

• Ya Li (YL):

0000-0003-0430-7926

Authors’ contribution

XH, JC designed this study and signifi-

cantly revised the manuscript; WD, YL per-

formed this study and wrote the manuscript.

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