At present, most countries have conducted GBS screening for pregnant women aged 35–37 weeks in the third trimester of pregnancy and conducted IPA for pregnant women infected with GBS. This measure effectively reduces the incidence of GBS in newborns. Penicillin is recommended as the first-choice drug for IAP in various countries [6–7].The global detection rate of GBS in pregnant women varies by region, and reports show that the colonization rate of GBS in pregnant women worldwide is approximately 17.4% (95% CI 16.3% -18.5%) [5].The overall colonization rate of GBS among pregnant women in China is 8.1% (95% CI, 7.2–8.9) [2], with the highest rate being 9.3% (95% CI 6.6–12.0) in the central region, followed by 8.3% (95% CI 5.5–11.0) in the eastern region, and the lowest rate being 6.8% (95% CI 5.4–8.3) in the western region [8].The GBS colonization rate of pregnant women in this study was 6.52%, which is lower than the domestic and global average. The differences in colonization rates among different studies or regions may be related to regional differences, detection methods (culture/PCR), sampling sites (vaginal/rectal sampling), and differences in sampling gestational weeks. It is also not ruled out that this may be related to pregnancy management and a decrease in the incidence of high-risk factors such as gestational anemia and prenatal care.
During pregnancy, high levels of estrogen and Progestogen lead to congestion and edema of vaginal folds, a decrease of barrier function, and a large amount of estrogen causes glycogen accumulation in Vaginal epithelium, and Progestogen promotes intracellular glycogen release, all of which provide conditions for the mass reproduction of GBS. Some studies have shown that the presence of old age, GDM, reproductive tract infection, obesity during pregnancy, previous abortion history, and other factors is more likely to cause an imbalance of Vaginal flora, which will lead to an increased chance of GBS infection in pregnant women [9–11].However, in this study, no association was found between advanced age, GDM, and GBS infection in pregnant women, consistent with the previous research findings [12].G.B.S. belongs to β Hemolytic streptococcus-like bacteria with a good affinity for chorion. It promotes the activation of Prostaglandin by producing many phosphatase A2, leading to inflammatory reactions around the cervix. At the same time, the invasion of G.B.S.-related metabolites can reduce the local tension of the fetal membrane and eventually cause premature rupture [13].There was no significant difference in the premature rupture rate of membranes between the GBS positive group and the control group in this study, which may be related to the higher GBS screening and IAP implementation rates.
Neonatal infection is one of the expected adverse outcomes of GBS infection during pregnancy. Without preventive measures, about 50% of the colonized women will vertically transmit GBS to the baby through contaminated amniotic fluid and body fluid before or during delivery, leading to invasive diseases of the newborn, such as pneumonia, neonatal sepsis and neonatal meningitis [14–15].Because compared with Neisseria gonorrhoeae and Escherichia coli, G.B.S. has more robust adsorption capacity and penetration to the chorion and can be carried to the placenta through lymph nodes or dendritic cells. Such placental colonization may increase the risk of Neonatal infection [16]. In this study, Neonatal infection was taken as the dependent variable, and G.B.S. infection, Vaginal delivery, and G.D.M. in the elderly and women in late pregnancy were taken as independent variables. The results showed that G.B.S. infection in women in late pregnancy was an independent risk factor for Neonatal infection.
In summary, clinical practice should attach great importance to GBS infection in late pregnancy, strengthen GBS screening in late pregnancy, and actively implement the strategy of intrapartum antibiotic intervention (IAP), which is of great significance in reducing the vertical infection rate of maternal and infant GBS and improving the quality of newborn birth.