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. GBS is a β-hemolytic gram-positive bacteria that colonizes the gastrointestinal and urogenital tracts. Pregnant women, newborns, and the elderly are susceptible [6]. At present, GBS has become one of the main pathogenic bacteria that cause perinatal infections in mothers and children. There has been a lot of research into GBS infection in pregnant women in recent years. According to recent studies, the colonization rate of GBS in pregnant women abroad ranges from 3.3–26% [7–9].
According to research into different Chinese regions, the prevalence of GBS infection in pregnant women in China ranges from 3.7–32.4% [10–13]. 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 fluid, and cesarean sections were all higher compared to GBS-negative 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 fluid pollution. Aspiration of fetal amniotic fluid 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 significant. There was no significant 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 confidence 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 significantly higher than the control group’s 4.05%. This finding 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 inflammation 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.