Impact of infectious factors in cervical and vaginal secretions and inflammatory parameters in pregnant women on preterm birth

Abstract

Introduction: Preterm birth is a significant clinical issue in obstetrics. According to the World Health Organization’s definition, it is characterized by the birth of a newborn after the twenty-second week but before the thirty-seventh week of pregnancy. Prematurity is associated with a significant increase in neonatal and infant mortality and morbidity, as well as long-term negative effects on physical and intellectual development. The direct causes of preterm birth include spontaneous preterm labor (sPTL), preterm premature rupture of membranes (PPROM), and medically indicated preterm termination of pregnancy. Inflammation within the reproductive system is considered the main cause of prematurity, accounting for 25–40% of preterm births. Intrauterine infection-related inflammation triggers the body’s inflammatory response, leading to preterm labor and the progressive dilation of the cervix. 
The aim of the study was to assess the impact of genital tract infections and elevated C-reactive protein (CRP) levels and leukocyte counts in pregnant women on the occurrence of preterm labor and preterm rupture of membranes leading to preterm birth. 
Materials and methods: The study was retrospective and included 206 pregnant women, divided into 2 groups: study and control group. The study group consisted of 133 women diagnosed with preterm birth, while the control group included 73 women who delivered at term. Statistical evaluation results were provided for the entire study group, and later stage s involved dividing the group into subgroups of patients with preterm birth due to sPTL and PPROM. 
Results: The most common pathogens found in the genital tracts of patients in the study group were Gram+ bacteria, which accounted for approx. 50.0% of infections. The second most common pathogens were mycoplasmas (22.56%), followed by Gram– bacteria 
(19.55%). In the subgroup of patients with preterm birth due to sPTL, Gram+ bacteria were identified in 53.85% of cases. In the subgroup of pregnant women diagnosed with preterm birth due to PPROM, Gram+ bacteria were cultured in 46.91% of swabs. Based on the obtained results of blood morphology with an automatic differential, it was found that the median white blood cells (WBC) values in patients with preterm birth due to sPTL were: at admission, 12.85 thousand/µL; on the day of the swab, 12.9 thousand/µL; and on the first day postpartum, 15.4 thousand/µL. Similar results were obtained in patients with preterm birth due to PPROM, where WBC values were: at admission, 12 thousand/µL; on the day of the swab, 12.9 thousand/µL; and on the first day postpartum, 15.55 thousand/µL. Analyzing CRP concentrations between the subgroups of the study group, it was shown that CRP levels on the day of admission (p = 0.004) and on the day of the swab (p = 0.042) were significantly higher in the sPTL group, at 6.15 mg/L and 6.3 mg/L, respectively, compared to the PPROM group, where CRP levels were 3.9 mg/L and 4 mg/L, respectively. 
Conclusions: 1. Acute-phase protein concentrations in serial measurements can be a very useful parameter for assessing inflammation and excluding infections within the genital tract in pregnant women. Additionally, fluctuating CRP levels coincide with preterm labor. 2. The duration of pregnancy is influenced by a positive culture result from genital tract swabs, regardless of the mechanism of preterm birth. 3. Further research should be conducted to effectively prevent preterm births.