On the Safety of COOK Double Balloons to Promote Cervical Ripening in Pregnant Women With Group B Streptococcus Colonization

Background: For pregnant women who develop complications during the third trimester of pregnancy, or who have not given birth naturally after more than 41 weeks of pregnancy, articial induction of labor is needed in order to obtain a healthy outcome for both the mother and the child. The 2014 edition of the Guidelines for Promoting Cervical Maturation and Delivery in Late Pregnancy point out that the use of COOK cervical ripening balloons to mechanically dilate the cervix can be used in the third trimester to promote cervical ripening and labor induction [1]. The disadvantage is the risk of infection, premature rupture of membranes, and umbilical cord prolapse [2]. The safety of balloon induction for pregnant women colonized by group B streptococcus (GBS) is currently lacking in multi-center clinical research data. This article will study the safety of COOK double balloon induction in pregnant women colonized by GBS. Methods: A total of 1,681 pregnant women who used COOK double balloons for cervical ripening in Changsha Maternity and Child Health Hospital from September 2018 to September 2020 were selected as the research subjects, from which 125 cases with colonization of group B streptococcus in the reproductive tract were selected as the observation group. Pregnant women without group B streptococcus colonization (N = 1556) served as the control group. This study compares the two groups’ delivery methods, postpartum complications, and neonatal conditions. Results: The rate of transition to cesarean section in the observation group was slightly higher, and the difference was statistically signicant (p = 0.049). The rate of postpartum hemorrhage was higher than that of the control group (p < 0.05). Although chorioamnionitis increased compared to the control group, the difference was not signicant (p > 0.05). The comparison of newborn birth indicators between the two groups showed no statistically signicant difference (p > 0.05). Conclusion: When pregnant women with colonization of group B streptococcus of the genital tract use the COOK double balloon to promote cervical ripening, the success rate of labor induction is high. Use of the balloon does not increase the cesarean section rate and the incidence of chorioamnionitis, nor

Inclusion criteria. (1) Gestational age ≥ 37 weeks, with indications for labor induction, but no serious maternal comorbidities and complications such as severe preeclampsia, diabetes with poor blood sugar control, and severe organ dysfunction; (2) Single live birth, head position, no contraindications for vaginal delivery such as placenta previa and vascular previa; (3) Cervical score: ve points; (4) No recent acute infection of respiratory tract, urinary tract, digestive teact ; (5) No chlamydia, herpes simplex virus, or other infections. Exhaust standard: Those who are allergic to penicillin.
Method. Both groups used the COOK cervical ripening balloon method. In this method, the patient takes the lithotomy position, the drape is routinely sterilized, the cervix is fully exposed, the double balloon is inserted into the cervical canal, and 80 ml of normal saline is injected into the piston marked with a red U and a green V. After ensuring that the water bladder is near the cervical canal, the end is xed onto the patient's inner thigh with tape, without restricting the patient's activities [3]. The balloon was placed at 20:00 and then removed at 08:00 the next morning, and the membrane was arti cially ruptured. If there were no regular contractions one hour after rupture, a small dose of intravenous oxytocin was used for cervical ripening. Penicillin was used intravenously to prevent infection 30 minutes before arti cial rupture. The rst dose was 4.8 g, and then a 2.4g dose was given every 4 hours until delivery.
Observation indicators. Delivery methods, postpartum complications during delivery, and birth conditions of newborns served as observation indicators in this study.
Statistical processing. This study uses SPSS 26.0 statistical software: (x̅ ±sd) for measurement data, independent sample t-test for comparison of means, χ2 test for comparison of rates. p-values < 0.05 are deemed statistically signi cant.

Results
Comparison of general conditions of pregnant women. The general information of the two groups of pregnant women includes age, gestation times, parity times, and gestational weeks of delivery. The difference was not statistically signi cant (p > 0.05). See Table 1 for details. Complications. The main comorbidities of the two groups of women undergoing COOK balloon induction of labor were hypertension during pregnancy, GDM, oligohydramnios, delayed pregnancy, and the composition ratio of ICP. The differences were not statistically signi cant between groups (p > 0.05). See Table 2 for details. Comparison of delivery situation. There was no signi cant difference in the incidence of chorioamnionitis between the two groups. The rate of cesarean section in the observation group was slightly higher than in of the control group, and the postpartum hemorrhage rate of women with GBS colonization increased signi cantly (p < 0.05). See Table 3 for details. Comparison of newborns' birth conditions. There was no signi cant difference between the two groups of newborns (p > 0.05) in the 1-minute and 5-minute Apgar scores, the incidence of fetal distress, as well as the incidence of neonatal infection, asphyxia, pneumonia, and other complications. See Table 4 for details.

Discussion
In postterm pregnancies, or in the event of comorbidities that risk termination of the pregnancy with no contraindications to vaginal delivery, in order to increase the vaginal delivery rate, different methods are selected for induction of labor according to the pregnant woman's cervical ripening. The current methods for promoting cervical ripening mainly involve prostaglandin preparations and mechanical dilatation.
Prostaglandin preparations include controlled-release dinoprostone suppositories and misoprostol. The disadvantage is that the rate of tonic contraction of the uterus is higher, and the incidence of fetal distress is increased [4]. Compared with dinoprostone suppositories, the cervical dilation balloon is a relatively mild means of inducing labor. The main mechanism of action is to simulate the fetal head continuously compressing the cervix, gradually softening and dilating the cervix through stable mechanical force while simultaneously stimulating the endogenous prostate. The synthesis and release of hormones induce uterine contractions. The operation is simple and safe, does not affect the daily activities of pregnant women, and can also reduce the risk of tonic contractions [5].
Infection is one of the main causes of adverse maternal and infant outcomes during the perinatal period. According to research into different Chinese regions, the prevalence of GBS infection in pregnant women in China ranges from 3.7-32.4% [10][11][12][13]. In GBS-positive pregnant women, the rate of neonatal infection and asphyxia, as well as the incidence of chorioamnionitis, puerperal infection, premature membrane ruptures, fecal staining of the amniotic uid, and cesarean sections were all higher compared to GBSnegative pregnant women. [14] [15]. GBS infection leads to premature rupture of fetal membranes. After the rupture of the membranes, pathogens continue to invade the uterine cavity, causing infections of the fetal membranes and placenta, thereby increasing the incidence of intrauterine infection. GBS can cause amniotic uid pollution. Aspiration of fetal amniotic uid during childbirth can lead to neonatal infection and neonatal pneumonia, which usually appear within 6 to 12 hours after birth, manifesting as symptoms of respiratory distress, hypotension, and unstable body temperature.
The CDC guidelines in the United States recommend that GBS-positive pregnant women be given prophylactic antibiotics during childbirth, and penicillin is recommended [16] [17]. McNanley et al. [18] state that antibiotics given four hours before delivery can reduce the vaginal GBS count by a factor of 50. For GBS-positive pregnant women, administering adequate penicillin as soon as possible after delivery can reduce the amount of GBS carried in the vagina and rectum of the mother. When the interval between starting penicillin and childbirth, is less than one hour, the vertical infection rate of the GBS-positive mother and infant is more than 40%. When that interval is increased to four hours, the vertical infection rate is reduced to 1% [19]. The results of this study show that the prevalence of chorioamnionitis (8.8%) in pregnant women with GBS colonization using COOK balloons to promote cervical ripening was slightly higher than that of pregnant women without GBS infection (6.23%), but the difference was not signi cant. There was no signi cant difference in neonatal birth score, incidence of fetal distress, and incidence of neonatal infection, asphyxia, pneumonia and other complications, which is considered to be a positive result of the active use of penicillin before delivery.
In this study, the cesarean section rate in the GBS group was 24%, slightly higher than 17% in the control group, and still lower than the total cesarean section rate of 29-31% in our hospital. In the GBS group, 10 primiparous women had no medical indications for cesarean section during vaginal delivery after the balloon was removed, but they refused to continue vaginal delivery and requested cesarean section. Parturients considering GBS colonization are concerned about the increased risk of fetal infections due to the prolonged labor process, and require cesarean section to end the delivery process as soon as possible. Therefore, the risks and countermeasures should be fully explained to GBS-positive women before introducing the COOK balloon, so as to enhance their con dence in vaginal delivery and reduce the incidence of caesarean section.
In this study, 11 cases of postpartum hemorrhage occurred in 125 pregnant women with GBS colonization, accounting for 8.8%, which was signi cantly higher than the control group's 4.05%. This nding is consistent with studies by Kwatra [20] and others. The causes of postpartum hemorrhage in the GBS group included seven cases of uterine asthenia, two cases of placental factors, and two cases of soft birth canal laceration. Among them, two cases were complicated with chorioamnionitis, accounting for 18.18% (2/11) of postpartum hemorrhage in the GBS group, which was much higher than the 9.52% (6/63) rate of postpartum hemorrhage and chorioamnionitis in the control group (p = 0.015). Considering that GBS colonized in the vagina, rectum, and urinary tract during pregnancy can spread ascending to infect the cervix, uterus and fetal membranes-soft birth canal due to in ammation and edema increased fragility, leading to soft birth canal laceration, thereby increasing the rate of postpartum hemorrhage; Intrauterine infection leads to uterine contractions. Fatigue also increases postpartum hemorrhage. Therefore, pregnant women with GBS colonization should receive active measures to prevent postpartum hemorrhage as soon as possible after delivery, including continuous uterine massage and medications to cause contractions, such as Carboprost tromethamineand ergonovine.

Conclusions
In summary, the application of COOK balloons to promote cervical ripening in pregnant women with GBS colonization of the genital tract can create conditions for vaginal delivery. Before the operation, it is necessary to fully evaluate the situation of the mother and child, and to inform the women and their families of the procedure's risks and countermeasures, thereby increasing their con dence in vaginal delivery. Treatment with antibiotics for more than four hours before delivery does not increase the risk of infection for pregnant women with GBS colonization or their children, but the rate of postpartum hemorrhage increases. Therefore, pregnant women who are colonized with GBS need to take more active and effective measures to prevent postpartum hemorrhage. In addition, whether combined GBS colonization can be an independent high-risk factor or a synergistic factor for postpartum hemorrhage needs to be further studied in future clinical work. All authors reviewed the manuscript.